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ALUMINUM CAN TECHNOLOGY TO MAINTAIN
COMPETITIVENESS BY REDUCING COST

By

Tatsuya Hanafusa

A THESIS
Submitted to
Michigan State University
in partial fulﬁllment of the requirements
for the degree of

MASTER OF SCIENCE

School of Packaging

1 996

ABSTRACT

ALUMINUM CAN TECHNOLOGY TO MAINTAIN
COMPETITIVENESS BY REDUCING COST

By

Tatsuya Hanafusa

Aluminum cans for beverages are one of the most popular forms of
packaging. In 1994, aluminum cans made up 72 percent of the US beverage can
market. The aluminum can has advantages, such as lightweight, excellent shelf
life, good recyclability and inexpensive price. This research focused on the cost
reduction of aluminum cans by reduction of weight. The highest fraction of a can
production cost is the aluminum metal cost, about 58 percent for a can body and
78 percent for a can end. Reducing the weight of aluminum metal has been a
primary approach to reducing the cost of the aluminum can since its introduction.
The weight of the can body has been reduced to 54 percent of the weight in the
early 1960’s.

The can body is divided into three parts in terms of weight reduction: thick
wall area, thin wall area and bottom area. The weight of each area can be reduced
by different technologies. By using a combination of technologies, it will be
possible to reduce the weight by about 11 percent in the near future.

The weight of the can end has bemn reduced to 45 percent of the weight in
the early 1960’s. There are two ways to reduce the can end weight, reduce the

diameter and the thickness of the can end. Reducing end diameter is more

effective because the reduction of the diameter enables a simultaneous reduction
in thickness. Over time, the diameter of the can end has decreased in steps from
211(2-11/16 inches) to 209, 207.5, 206, 204, 202. Further switch to a 200(2
inches) diameter end is expected and will be required to further reduction of the
cost.

The total expected weight reduction of aluminum can is around 11 ~ 12
percent. However, the ﬂuctuation of the aluminum metal price may be large
enough to counteract the can weight reduction. Therefore, not only weight
reduction, but also recycling or increasing the attractiveness of aluminum cans will

be important to maintain the competitiveness of aluminum cans in the future.

ACKNOWLEDGMENTS

I would like to express my hearty appreciation to my major professor, Dr.
Harold A. Hughes (School of Packaging) for his valuable advice and guidance
through the graduate program.

I also thank my committee members, Dr. Gary Burgess (School of
Packaging) and Dr. William Haines (Department of Agricultural Economics) for

their assistance.

TABLE OF CONTENTS

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

List of tables vii
List of ﬁgures viii
Chapter 1 1
Introduction 1
History of aluminum cans for beverages 1
Aluminum beverage can market in USA 8
Cans for soft drinks and beer 12
Objective 19
Chapter 2 20
Literature review 20
Aluminum can body 20
Aluminum can end 21
Aluminum can forming process 22
Other information sources 23
Chapter 3 26
Aluminum can manufacturing 26
Aluminum can manufacturing process 26
Aluminum Can body Line 26
Aluminum Can end Line 41
Aluminum metal for beverage cans 43
Aluminum alloys for can bodies 43
Aluminum alloys for can ends 45
Chapter 4 48
Light Weighting 48
Can body lightweighting 52
Can wall thickness reduction 54
Thin-wall 56
Thick—wall (Neck Wall) 57

Bottom thickness 58

Can End Lightweighting 61

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chapter 5 64
Recycling 64
Packaging materials in the municipal solid waste 65
Recovery of aluminum metal from municipal solid waste 68
Aluminum used beverage can recycling business 69
Aluminum metal price and recycling 71
Recycled content of UBC in new cans 74
Aluminum can recycling problems to be solved 77
Chapter 6 79
Further can weight reduction 79
Price competitiveness 79
Can weight reduction 80
Can body weight 84
Thin wall thickness and weight 90
Reduction of the thin wall 92
Resistance to hoop stress 97
Neck wall weight and thick wall thickness 105
Die-necking process 109
Spin-necking process 1 12
Spin-flow-necking process 114
Neck wall weight reduction 116
Can body bottom weight 120
Bottom shape 120
Bottom thickness and metal strength 123
Bottom reforming 126
Can end weight reduction 130
Aluminum metal for cans 132
Chapter 7 138
Discussion and conclusion 138
Aluminum can market
1 3 8
Cost of aluminum can 138
Reduction of aluminum weight 138
Future weight reduction 140
Effect of aluminum metal price 141
Future aluminum can 143
References 146

vi

Table 1-1
Table 1-2
Table 1-3
Table 1-4
Table 3-1
Table 3-2
Table 3-3
Table 3-4
Table 4-1
Table 4-2
Table 5-1
Table 5-2
Table 5-3
Table 5-4
Table 5-5
Table 6-1
Table 6-2
Table 6-3
Table 6-4
Table 6-5
Table 6-6

Table 6-7

LIST OF TABLES

 

 

 

 

US food and beverage container market 10
US can shipments by sector (Millions) 12
US Beer container market share 15
US soft drinks container market share 16
Nominal Composition of Aluminum Alloy for can body 43

 

Mechanical properties of aluminum alloys for can bodies -—----45
Guaranteed chemiwl composition of aluminum alloys for can ends 46

 

 

 

 

 

 

Mechanical Properties of aluminum alloys for can ends 47
Aluminum can body cost (206/211 330ml can) 49
Aluminum end cost (Diameter 206) 49
Aluminum Products in MSW, 1993 68
Processing costs vs. prices of recycled materials 71
Aluminum alloy components list (weight %) 74
Calculated components of recycled aluminum from UBCs --75

 

Example of component of recycled aluminum metal from UBCs ---76
Thin wall thickness history 92
Can body dimension and performance example 94
Example of Neck thickness 106
Example of thick wall thickness (Neck wall thickness) history ----106
General Necking Steps for Each Reduction 108
The number of the die necking process required to make 204, 202

neck with various thick wall thickness
Bottom performance of reformed bottom

 

 

 

 

 

116
128

 

vii

LIST OF FIGURES

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 1-1 US Packaging Market in 1993 9
Figure 1-2 US Metal Food and Beverage Can Market 11
Figure 1-3 Beverage can shipments in US 14
Figure 1-4 Metal cans and non-retumable glass market trend for beers in US -17
Figure 1-5 Metal cans and PET bottles market trend for soft drinks in US ---18
Figure 3-1 Typical aluminum can body line 30
Figure 3-2 Typical aluminum can end line 31
Figure 3-3 Drawing process ( 1) 32
Figure 3-4 Drawing process (2) 33
Figure 3-5 Drawing process (3) 34
Figure 3-6 Drawing process (4) 35
Figure 3-7 Drawing process (5) 36
Figure 3-8 Redrawing and Ironing Die Set 37
Figure 3-9 Ironing Process 38
Figure 3-10 Ironing Process, Magniﬁed picture 39
Figure 3-11 Bottom forming 40
Figure 4-1 Aluminum can weight history (12-ounce can) 51
Figure 4-2 Aluminum can body lightweighting history 53
Figure 4-3 Can Cross-sectional Proﬁle 55
Figure 4-4 Bottom cross section 59
Figure 4-5 Bottom reforming 60
Figure 4-6 Aluminum can end weight history 63
Figure 5-1 Sources of Landﬁlled Waste 66
Figure 5-2 1993 recovery rates for selected components of municipal solid waste

(percentage of total generation) 57
Figure 5-3 Aluminum metal prices, LME prices vs. UBC prices 73
Figure 6-1 Can Body Classiﬁcation 81
Figure 6-2 Can end classiﬁcation and name of dimension 82
Figure 6-3 Can weight reduction : Relationship diagram of factors 83
Figure 6-4 Typical can body dimension, 202/211 12-cunce can 85
Figure 6-5 Aluminum can weight break down, 202/211 12-ounce 88
Figure 6-6 Thin wall thickness vs. Column Strength (Axial Strength) -------95
Figure 6-7 Maximum hoop stress (at 6.3 kg/cmz) vs. Thin wall thickness --—-98
Figure 6-8 Tensile strength and hardness, 3004-H19 100
Figure 6-9 Work hardening of can body 101
Figure 6-10 Can body hardness after baking and before necking 102

viii

Figure 6-11 Thin wall weight vs. thin wall thickness 104

 

 

 

 

 

 

 

 

 

 

 

 

Figure 6—12 Die-necking 111
Figure 6-13 Spin-necking 113
Figure 6-14 Spin-ﬂow-necking 115
Figure 6-15 Neck weight (Neck length is 21.1mm) 119
Figure 6-16 Typical can bottom shape 122
Figure 6-17 Buckling pressure vs. bottom thickness for commercial can bodies

125
Figure 6-18 Bottom reforming process 127
Figure 6-19 Bottom weight vs. Bottom thickness 129
Figure 6-20 End diameter and thickness trend 132
Figure 6-21 Aluminum Metal price 135
Figure 6-22 Aluminum an shipment and recycling rate 136

Figure 6-23 Aluminum metal price and UBC (used beverage can) price 137

 

Chapter 1

Introduction

History of aluminum cans for beverages

The aluminum can is one of the most popular and dominant forms of
packaging for beer and soft drinks. The history of the aluminum beverage can
began in the mid 1900’s, less than 40 years ago. However, steel cans were used
earlier for beverages.

In 1909, a Montana brewer made the ﬁrst inquiry about the use of metal
cans for beverages. He wrote to the American Can Company, one of the largest
commercial can manufacturers in the USA at that time, asking if cans were
available for packaging beer. Of course, beer cans were not commercially
available at that time. But researchers at American Can had made experimental
cans for beer. The results had been unsuccessful and a negative reply was
returned to the brewer(1-1). Twenty years later, Anheuser-Bush and Pabst also
tried and failed to develop a metal beer can.(1-2).

One of the primary difﬁculties was the inability of the cans to withstand the
pressure during pasteurization process. Beer eons must withstand an internal
pressure as high as 5.6 kglcm2 (80 psi), much higher than the pressure used for
ordinary food cans (around 2.8 kglcmz).

The taste or ﬂavor of beer is very sensitive and changes when exposed to

steel. To protect against the effect, manufacturers tried using tin plated steel, but it

2

wasn’t satisfactory. There were enough ﬂaws in the coating to negatively affect
the taste.

In 1933, the Gotfried Krueger Brewing Company of Newark, NJ, test ﬁlled
12-02‘” (355 ml) three-piece steel cans, made by the American Can Company,
and delivered them to beer drinkers, along with questionnaires asking their
opinions about beer in cans. Two years later, in 1935, the same Gotfried Krueger
Brewing Company test-marketed the ﬁrst commercial beer in cans in Richmond,
VA. They had made two signiﬁcant improvements to the cans. They developed a
stronger seam for the three-piece steel can and applied a two-layer coating on the
internal surface of tin plated steel with “Vinylite”, a vinyl copolymer (synthetic
plastic) which was developed by Carbide and Carbon Company to prevent off-
ﬂavor(1-3). Later, still in 1935, following the lead of G. Kerueger Brewing and the
American Can Company, other breweries and can manufacturers engaged in the
canned beer business. In 1935, more than 200 million cans were sold to 23
brewers. They were all of the tin plated steel three-piece type.

The ﬁrst canned soft drink was test-marketed by Clicquout Club in 1936.
Coca-Cola test-marketed 474 ml (16 oz) and 947 ml (32 oz) cans in 1941, but
postponed the launch of armed soft drinks because of the metal shortage during
the war (1 -4).

The history of the D&I aluminum can (drawing and ironing can) was
started by Jakob Keller in Switzerland during World War II. At that time,

Switzerland was almost totally cut off from imports and ran short of tin plated steel

( 1) Since the term 12-oz occurs many times as a descriptive term, the metric equivalent will
not be expressed.

3

to make cans. However, Switzerland had aluminum available. Jakob Keller, a
consulting engineer in Zurich, Switzerland, proposed using aluminum to make
cans instead of tin plated steel, but few people believed it would be possible
because aluminum didn’t seem to have enough strength and was very expensive
when compared to steel (1-5). Keller was issued the ﬁrst D&l patents in 1944
and 1947. He used a horizontal press to make cans. The process formed a circle
of aluminum sheet into a shallow cup and then stretched the cup by using 2 or 3
ironing dies. He discovered that the ironing die required a sharp edge proﬁle to
effectively thin down the walls of the aluminum cups. At that time, Keller was using
soft tempered pure aluminum instead of a work hardened aluminum alloy (1-5).
Switzerland used the drawn-redrawn cans for packaging condensed milk during
World War II. The D&I process was suited to making pressurized cans, but beer in
cans was not imaginable in Europe at that time. After the end of World War I I, the
attraction of the aluminum can faded when tin plated steel again became
available.

At that time, Alcan had an ofﬁce in Zurich and supported Keller’s work.
Sometime later, Alcan established a can laboratory in a research center in
England where they installed a Keller D&I press and an impact extrusion press.
They promoted the potential beneﬁts of aluminum cans to companies in the US,
and several of the companies started to research aluminum cans as a result.
Among them were Coors, Kaiser and Reynolds. Kaiser and Coors worked in
parallel. Kaiser pursued the D&I process and Coors worked with the impact

extrusion process(1-5).

4

In the 1950s, Coors was still a regional brewery, distributing lager to
eleven westem states and attempting to expand into other markets. Coors was
less devoted to bottles and more committed to cans than other brewers. In spite of
all the advances in can making over the years, the beer can was still an imperfect
container. Beer was sometimes exposed to steel which caused the wer to cloud
and gave it a metallic taste. In addition, the three-piece steel cans available at that
time were of indifferent quality with a tendency to leak through the body seam and
the top and bottom lid seams. Coors initiated research to develop better beer cans
to solve these problems because cans were the brewery’s single largest expense
(1-6). Coors established a company called Aluminum lntemational in conjunction
with Beatrice Foods and Bronsten. They bought impact extrusion equipment from
Germany and supplementary equipment from Italy and set up an impact extrusion
can line (1-7). Coors and Aluminum lntemational made aluminum cans for Primo,
small Hawaiian brewery. They test-marketed in 1958. This was the ﬁrst use of
commercial aluminum oons for beverages. The Coors aluminum can, which
debuted in January 1959, was a 7-ounce impact extruded beer can. It went on the
market nearly 24 years after the ﬁrst steel cans for beer had been introduced to
the worid(1-8). The impact extrusion method was never suitable to be scaled up to
full-size cans. The process was too slow and it required the use of pure aluminum,
which was soft and had difﬁculty holding its shape and withstanding the internal
pressure after being ﬁlled with beer. To compensate for these defects, impacte
extruded cans had to have a relatively thick wall. In fact, that original 7-ounce can

weighed more than a modern 474 ml (16-ounce) can (1-8). The impact extrusion

5
process produced a side wall of uniform thickness from the bottom of the wall to

the top ﬂange. The thickness of the can wall was determined by the thickness of
the can ﬂange to which a lid (a can end) was seamed after the can was ﬁlled. The
can’s side wall didn’t need to be as thick to withstand the internal pressure, so
there was unnecessary metal on the can wall and it was less economical. After
recognizing the shortcomings of their process, Coors began looking for an
alternate can manufacturing process.

Kaiser Aluminum set up a can development center in Chicago in 1956 and
concentrated on the D&I process. The big advantage of the D&I process was that
it allowed control of the distribution of metal along the side wall of a can. The neck
and bottom side wall areas could be thicker than the middle portion of the side
wall. Kaiser used an aluminum-magnesium alloy, 3004-O, with soft temper instead
of pure aluminum(1-9). The 3004 alloy is still one of the standard materials for
aluminum can manufacturing. The alloy was stronger than pure aluminum, so cans
could be lighter in weight without losing their shape or strength to withstand the
internal pressure and the axial load during seaming. A pilot scale can line was set
up at the'Kaiser Wanatah facility in Indiana. However, the major can makers, who
were still committed to tin plated steel cans, opposed Kaiser’s aluminum can
development. They threatened Kaiser Steel with cancellation of all tin plate orders.
Kaiser followed their “suggestion” and terminated development work on the
aluminum can. Several members of the development team promptly moved to
other companies which were still interested in aluminum can manufacturing. Some

of the former Kaiser employees took their expertise to the Reynolds Metals

6

Company, which became the ﬁrst commercial producer of 12-cunce aluminum D&I
cans in 1964 (1-10).

Reynolds also started their development effort with the extrusion process.
After the former Kaiser researchers joined the company, Reynolds changed the
direction of their efforts. They built D&I presses and set up a pilot line at their
equipment center. They made 12-ounce beer cans from 3004 half hardened sheet
in 1964 (1-11). The cans were not necked down at that time. This was the ﬁrst
12-ounce aluminum two piece can with 211 diameter (2 11l16 inches diameter,
about 68 mm) and it became an industry standard size for beverages.

Meanwhile, Coors replaced the impact extruders on their 207 ml (7-ounce)
aluminum can line with Kaiser D&I presses. In 1966, they set up an 11-ounce line
in a new can plant (1-12). At that time, Reynolds had already introduced the 12-
ounce aluminum can for beer and it had become the industry standard size.
Therefore, Coors also had to again convert their equipment to adopt the 12-ounce
size. These circumstances still left Coors with a non-standard can which had a
different height and diameter than the industry standard which was a 12-cz can
with a 211 diameter. Since Coors used the aluminum cans to package their own
beer, there was no problem with this difference and they continued to use the
non-standard 12-ounce cons.

SOOn after the major can manufacturers entered the aluminum two piece
can business, the industry initiated an ongoing program of developments to reduce
costs because aluminum is a relatively expensive packaging material. The efforts

focused on weight reduction and improvement of can production efﬁciencies.

7

There were few changes which increased costs until recently. One was the
introduction of “Stay-on-tab” which was introduced to reduce the littering of tabs.
The “Stay-on-tab” was developed by the Reynolds Metals Company in response
to complaints from the public about tab littering, but it also increased the can
weight and cost. Other than that example, most of the developments were aimed
at cost reduction. Manufacturers reduced the can side wall thickness, bottom
thickness and end thickness. They changed the bottom shapes to get higher inner
pressure resistance and reduced end diameter to save material. Initially, the end
diameter, denoted the 211 end, was same diameter as the an body. End
diameters were mduced in steps from 211 to 209, 207.5, 206, 204 then 202.
Currently, 204 ends are used for beer and 202 ends are used for soft drinks in the
US.

In 1994, 106 billion aluminum cans were used in the US. Canned beers
held 60.8% of the total beer market and canned soft drinks held 53.7 % of the total
soft drink market(1-1.3). Aluminum cans are clearly the dominant form of
packaging for beverages.

The largest portion of the cost of an aluminum can has continued to be the
aluminum metal. Fluctuation of aluminum prices directly affects the cost of cans.
The price of aluminum metal started to increase in 1994, causing the price of cans
to increase. As a result of the price increases, the competitive position of
aluminum cans has been declining in comparison to other containers such as
glass and PET bottles. As a result, can manufacturers are again emphasizing

further efforts at cost reduction.

8

Aluminum beverage can market in the USA

Metal cans, the second largest sector of the packaging industry following
corrugated paper packaging, represent over 18 percent of the package market in
terms of sales dollars, as shown in Figure 1-1. Aluminum cans are used primarily
as containers for food, especially beverages. The overall rigid food and beverage
container industry, including metal cans, glass bottles, jars, plastic containers and
paperboard cartons, had an average growth rate of 3.3 °/o annually between 1988
and 1993. Each segment of the rigid food and beverage container industry has
competed to win a larger share of the market. Table 1-1 shows the size of each
market segment and the rate of increase for the last 13 years. The table shows
that metal cans have historically held the largest share of the food and beverage
container market, but have been losing market share since the middle 1980’s.
The rate of increase in the sales of metal container market is relatively low
compared to the rate of increase in plastic packaging.

Figure 1-2 shows a breakdown of the can market. Aluminum cans have
had a dominant share of the beverage can market and consumption has been
growing steadily since the late 1970’s. Steel cans have lost market share in the
beverage market but still are dominant in the food can market.

Table 1-2 shows US can shipments by sector for the last four years. In
1994, beverage cans made up 74 percent of the US can market and food cans
represented 26 percent. The can market grew steadily during these four years.

The increase in aluminum can shipments during these years was mainly the result

9

of the increase in use for beverages, especially soft drinks. Shipments of cans for

beer have been declining.

Paper
Flexible Closures Paper
5°/ 4% '
Glass 0 ‘ Corrugated
30%

  
   

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Figure 1-1 US Packaging Market in 1993
source: Industry, Goldman Sachs estimates (1-14).

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Table 1-2 US can shipments by sector (Millions)
Year 1991 1992 1993 1994
Total Shipments 129248 130685 132148 139254
Beverage (total) 94651 95678 97605 103119
(73.2%) (73.2%) (73.9%) (74.1 %)
Soft drinks 55821 57449 60074 66325
Beer 38830 38229 37531 36794
Others (total) 34597 35007 34543 36153
(26.8%) (26.8%) (26.1%) (26.0%)
Vegetables/juices 9982 9466 8739 9738
Pet foods 6061 6703 7000 7389
Other foods 5618 5568 5603 6063
Fruit/fruit juices 3192 3000 3009 2463
Aerosols 2653 2843 2785 2914
Seafood 1788 1907 1880 1906
Meat and poultry 1296 1435 1452 1782
Babyfoods 1101 1116 1134 1040
Dairy products 1051 1008 1015 1010
Material used
Steel 35276 3521 1 34156 33240
L27.3%) 426.9%) (25.8%) (23.9%)
Aluminum 93972 95469 97992 106014
(72.7%) 473.1%) (74.2%) (76.1%)

 

 

 

 

 

 

Source: Can Manufacturers Institute

 

13

Cans for soft drinks and beer

As shown in Table 1-2, about three-quarters of all cans are used for
beverages, soft drinks and beer. Both beverages contain carbon dioxide which
produces pressure in the cans. Carbonated products are suitable for aluminum
cans. The aluminum can wall is too thin to provide enough strength to support
normal stacking loads. The pressure is needed to support loads. Therefore, if
aluminum cans are used for beverages without wrbon dioxide, liquid nitrogen is
usually used to create the needed internal pressure.

The shipments of cans for soft drinks increased steadily until recently, but
the market for beer in cans has been declining for several years. Figure 1-3 shows
the trends in beverage can shipments for the last six years. Can shipments
increased during each of these six years, except for 1995. In 1995, total can
shipments decreased in comparison to the previous year. However, the simple
statistics do not reveal the entire story. In early 1994, the price of aluminum
increased sharply. Alert can users bought extra supplies of cans before the
increase in the price of aluminum affected can prices and stockpiled them for later
use. This pre-buy in 1994 was estimated to be as high as 3.2 billion cans (1-15).

If the data are adjusted to compensate for this pre-buying, aluminum can usage for

beverages increased in each of the last six years.

14

Beverage can shipments in US

 

Ll Beverage El Soft drinks & juice I Beer)

 

1 10
1 00
90
80
70
60
50
40
30
20

 

 

 

 

Billions of cans

 

 

 

1990 1991 1992 1993 1994 1995
Year

Figure 1-3 Beverage can shipments in US
Source: MPC Chronicle, March 1996 (1-15)

Table 1-3 shows the share of the beer market held by each type of
container. Aluminum cans were used for 60.4 percent of US beer production
(including draft). The second position was held by glass bottles. Table 1-4 shows
the relative amounts of each type of container used for soft drinks. The aluminum
can share was 53.7 percent of the US soft drink container market in 1994. The
PET (Polyethylene terephthalate) share of the soft drink market has been

increasing rapidly for the last four years. The increase in the PET bottle shipments

for soft drinks is a direct threat to the aluminum can industry.

15

Figure 1-4 shows

the metal can market and the non-retumable glass bottle market for beer. As

shown in Table 1-3, about 99 percent of the metal cans for used for beer are

aluminum. Therefore, the graph if Figure 1-4 can be regarded as that of “aluminum

mns vs. glass bottles for beer containers”. The aluminum can has been gradually

losing its market and the glass bottle has been gradually gaining.

Figure 1-

5 shows the metal can market and PET bottle market for soft drinks. As shown in

Table 1-3, about 95 percent of the metal containers for soft drinks are aluminum

cans. Therefore, Figure 1-5 shows nearly the same trend as that of “aluminum

cans vs. PET in soft drink container market”. The consumption of both aluminum

cans and PET bottles have been increasing for several years, but the rate of

increase in PET bottle shipments is higher than the rate for aluminum cans.

Table 1-3 US Beer container market share

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(12-Ounce Equivalent, %)
Year 1987 1988 1989 1990 1991 1992 1993 1994
Can (100%) 62.7 63.0 62.9 63.6 64.2 62.4 61.2 60.8
Aluminum (%) 100.0 99.7 99.0 99.0 99.0 98.9
Steel (%) 0.0 0.3 1.0 1.0 1.0 1.1
Glass (100%) 25.5 25.6 26.0 25.3 24.5 26.0 27.5 27.8
NR Glass (%) 97.2 97.2 97.1 97.8 97.3 97.3 96.8 97.2
R 6'3.“ (%) 2.8 2.8 2.9 2.2 2.7 2.7 3.2 2.8
Draft 11.8 11.4 11.1 11.1 11.3 11.6 11.3 11.4
Source: Beverage Industry; Business Trend Analysts

Can Manufacturers Institute; Business Trend Analysts (1-16)

16

 

 

 

 

 

 

 

 

 

 

Table 14 US soft drinks container market share
(12-Ounce Equivalent, %)
Year 1 989 1 990 1 991 1992 1 993 1 994
Can J100%) 47.9 50.4 51.3 52.5 53.2 53.7
Aluminum (%) 92.5 92.3 95.0 95.5 96.5
Steel GEL 7.5 7.7 5.0 4.5 3.5
PET 30.6 30.2 31.9 35.0 37.9 39.3
Glass (100%) 21.5 19.3 16.8 12.5 9.0 7.0
NR Glass (%) 59.5 67.4 69.0 74.4 80.0 84.3
R Glass (%) 40.5 32.6 31.0 25.6 20.0 15.7

 

 

 

 

 

 

 

 

Source: Beverage Industry; Business Trend Analysts
Can Manufacturers Institute; Business Trend Analysts (1-16)

 

17

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1 9
Objective
The goal of the research reported in this thesis was to evaluate and
discuss the factors that have affected the ability of aluminum cans to gain and
maintain competitiveness, especially the cost oompetitiveness gained by
lightweighting. The speciﬁc objectives are:
1. To survey trends in the aluminum beverage can market.
2. To identify and evaluate methods which have been used to reduce
the costs of aluminum beverage cans.
3. To identify and evaluate techniques used to reduce the weight of
aluminum cans.
4. To determine the effect of the price of aluminum metal on the price
of aluminum beverage cans.
5. To predict the potential for future weight reduction and cost saving

for aluminum cans.

In this paper, the discussion of can manufacturing production costs other
than the cost of the aluminum metal have been excluded. Those costs are speciﬁc
to each manufacturer. The discussion is focused on the general trends affecting

the can itself, especially can weights in the past and the future.

Chapter 2

Literature review

The technical literature about aluminum beverage cans is limited. Most of
the available papers have been written by researchers or engineers in the
aluminum can industry or the aluminum metal industry. Some of them have been
written to emphasize the advantage of certain products, machines or technologies~
over those of other companies. The aluminum can companies occasionally publish
papers about forming processes using their machines to emphasize their
advantages. Recently, there has been a trend toward reducing can end diameters,
so papers about can body neck reducing processes have been published.

The following section describes and discusses recent papers about

aluminum cans.

Aluminum can body

Smith (1995) discussed and summarized some of the major forrnability
barriers that limit lightweighting aluminum mns(2-1). He presented a summary of
the history of aluminum can body lightweighting and classiﬁed aluminum can body
lightweighting into three categories, thick wall thickness, thin wall thickness and
dome gauge (can body bottom thickness). He discussed smooth die-necking
technology which enables neck reduction from 211 diameter to 204 or 202
diameter. Suggested number of steps of die-necking, diameter reduction for each

step, and thick wall thickness were shown in the paper. Required steps for neck

20

21
reduction with 0.167 mm of thick wall from 211 to 204 was nine steps and

that for 202 is twelve steps. He further showed that if a thinner thick wall is used
for necking, more necking process steps will be needed.

Smith pointed out that the end diameter for soft drink cans has been
reduced to 202 and that a new can bottom design with a smaller base diameter is
required as a result to facilitate stackability. However, cans with smaller base
diameters tend to have wrinkles on the bottom. To solve this problem, he

recommended the introduction of a process using a pre—fonned cup.

Aluminum can end

Biondich(1989) discussed the shell forming process for an ends (2-2).
He introduced a newly designed reformed shell, and discussed advantages of
reforming the shell, the process used for reforming, and computer simulation of the
reformed shell. The advantage of the reformed and is that reforming process can
make a deep countersink without thinning the panel wall. The conventional shell
process uses one-step forming. If the countersink is deepened to increase
pressure resistance, thinning occurs at the panel wall due to restrained metal flow
and it is difﬁcult to get satisfactory pressure resistance. The reforming process
uses two steps to make the countersink without creating tensile stress at the panel
wall. Therefore, no thinning will occur. Biondich emphasized cost saving of

reformed shells due to lightweighting.

22

Aluminum can forming process

Lee and Payne (1993) introduced and discussed the spin-ﬂow—necking
process which is used to reduce the neck diameter of cans (2-3). The process was
ﬁrst introduced on a production line in 1992. Advantages of the spin-ﬂow process
were discussed. Spin-ﬂow necking is a tension process which is tolerant of thick
wall variation and defects in the can body. Thick wall variations of :I: 0.013 mm
were acceptable, whereas normal acceptances were 1: 0.008 mm. The tension
process allows the manufacturer to use a shorter can height. The can height for a
204/211 12-ounce spin-ﬂow-necked can is around 123.19 mm, about 0.38 mm
shorter than a spin-necked can and 0.64 mm shorter than a smooth die-necked
can. Those characteristics enable further lightweighting and saving cost. The
paper showed the detailed function of each die and included an explanation of the
spin-flow process.

- Jowitt (1993) discussed can bottom reforming (2-4). In the continuing
efforts to reduce the weight of the aluminum two-piece can, the ability to create an
improved bottom proﬁle is becoming an important factor. He described a process
that allowed further lightweighting of can bodies by reforming can bottoms. The
process of reforming bottoms involves reshaping the stand area of the can
bottoms. A smaller stand area radius increases inner pressure resistance of the
bottom. However, conventional bottom forming processes have limitations in their
ability to shape the stand area and the radius. The bottom reforming process adds

another opportunity to form the bottom and gives further freedom in shaping the

bottoms. In the paper, the effect of the reforming was 16.5 percent increase in

23

buckling pressure of the bottom. The target of the reforming was reducing
aluminum sheet thickness for can bodies from 0.300 mm (0.0118 inches) to 0.280
mm (0.0110 inches) with same bottom shape and material. This reduction in
thickness lead to a seven percent material saving.

Jowitt (1995) discussed forming processes, including spin-necking, for
metal can manufacturing (2-5). The spin-necking process for necking a 211 can

body into a 202 neck was described as follows.

Die-necking d Spin pre-necking I} Spin-necking and Flanging

Two or three steps of die-necking were required for ﬁrst stage, depending
on material and wall thickness. It was emphasized that a signiﬁcant number of can
manufacturing lines in Europe and in the US were running the spin-necking

machine.

Other information sources

Most of the papers on can manufacturing, including those discussed in the
preceding section, were written for specialists in the aluminum can industry.
Therefore, the contents are about specialized technological topics.

Most of the research and technological development has been done by
aluminum metal or aluminum can companies instead of public organizations or
institutes. Competition has been an issue. This situation has decreased the

number of the papers about aluminum cans.

24

Other information sources include industrial or trade magazines. There are
three magazines which emphasize information about the can industry: “The
Canmaker”, “The Canner’ and “Cantech lntemational”.

The Canner (1995) (2-6) discussed price trends of beverage cans. In 1994,
aluminum cans were the lowest cost choice with a price of $56.56 per 1000 cans,
compared to $60.77 for steel cans, $71.01 for PET containers and $95.99 for
glass bottles. However, since the beginning of 1994, the price of aluminum metal
has been increasing. By 1995, aluminum cans had lost price competitiveness with
a price $70.58 per 1000 cans, compared to steel cans at $65.58, PET bottles at
$70.6, and glass bottles at $95.22. The Canmaker (1995) (2-7), discussed prices
for aluminum metal aluminum cans. They predicted that the price of aluminum can
sheet would rise by 60 percent during 1995.

Cantech lntemational (1995) (2-8), discussed the availablility of alternate
containers, since aluminum cans had lost price competitiveness, such as glass
bottles for beer or PET bottles for soft drinks.

The articles in magazines usually discussed economic situations or trends
and showed little speciﬁc explanation of factors related to can manufacturing
technologies with data. Magazines tend to pick up the tOpics currently popular.
Therefore, the contents tend to focus on the temporary topics and narrow areas
and sometime they are too vague to understand the whole trend because of lack

of technological explanation and speciﬁc data.

25

So far, no comprehensive papers are known about aluminum can cost
reduction which include the trends of the recent technologies for lightweighting,
aluminum metal cost and aluminum prices.

This paper focuses on a comprehensive study of aluminum beverage can

technological trends, including lightweighting for cost saving.

Chapter 3

Aluminum can manufacturing

The Aluminum can manufacturing process

An aluminum two piece can literally consists of two parts, a can end (lid)
and a can body. The process of can end manufacturing is similar to the process
used for other types of cans, such as food cans. Aluminum can ends are often
used on steel two-piece or three-piece cans. Aluminum can bodies are made by a
unique process not used for other cans, such as steel three-piece cans or two-
piece draw-and-redraw steel cans. The ironing process is used for making the
aluminum can body. The process and equipment for can body and can end

manufacturing are shown in Figure 3-1 and 3-2.

Aluminum can Body Line

The aluminum can body manufacturing line is relatively large and long
compared to lines for other containers or can ends. The capital investment for a
new can body line may be as high as 30~40 million dollars today. To reduce the
cost of the cans, line speeds have been increased. In the early 1980's, a common
speed was around 800 cans per minute. Manufacturing rates in excess of 1600
cans per minute are common today. The function of each step in the process of

making a can is explained in the following section.

26

27

. Lubricator

Add lubricant to aluminum sheet for drawing.

. Cupper (Cupping Press)

Blank the aluminum sheet into circles and draw them into shallow
cups.

. Bodymaker (Redraw and Ironing Press)

Redraw the cups and iron into cans. The can body wall and bottom is
formed in this process.

. Trimmer

Trim the top of the cans to the speciﬁed height.

. Washer

Wash the cans to remove lubricant and contamination and apply
surface treatment to improve corrosion resistance and adhesion of
coating, then dry the cans.

. Base Coater

Apply white coating to improve the quality of color.

This process is for special design products.

. Base Coater Oven

Dry and cure the base coating.

. Decorator

Print and apply varnish on the cans.

. Decorator Oven

Dry and cure the ink and varnish.

28
10. Inside Spray

Spray coating on the inside of the cans.
11. Inside Spray Oven

Dry and cure the inside coating.
12. Necker & Flanger

Form neck and ﬂange.
13. Tester

Check the cans for pin holes or cracks.
14. Palletizer

Stack the cans on pallets.

The process step which differentiates the manufacturing of aluminum two-
piece cans from other two-piece cans, is the ironing process in the bodymakers,
the redraw and ironing presses. The aluminum sheet is ﬁrst drawn into shallow
cups in the cupper. The cups are then redrawn and ironed into cans by the
bodymakers. The drawing process is illustrated in Figures 3-3 and 3-7.

Drawing and ironing forming is limited in the amount of forming reduction
that can be done. The limit is called the limiting draw ratio or limiting ironing ratio.
Drawing the aluminum circle into a cup with the same diameter as the can and
ironing the deep cup into a can exceed the limits of the limiting draw ratio and the
limiting ironing ratio, respectively. Therefore, each forming operation needs to be
done in multiple steps. The drawing process is usually done twice to reduce the

aluminum circle into a can and the ironing process is usually done three times in

29

one pass of a punch to achieve the desired can wall thickness. Figure 3-8 shows
the die set for the redrawing and ironing process. Figures 3-9 and 3—10 show the
ironing forming of the can body. The bottom of the can body is also formed by the

bodymaker at the end stroke of the punch as shown in Figure 3-11.

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41

Aluminum Can End Line

Figure 3-2 shows the process of a typical can end manufacturing line. Each
process is explained below.
1. Shell press
Blank out circles from aluminum sheet and make shells for ends.
2. Curler
Roll the edge of the shell with a curl shape which is important for
seaming the end to a can body.
3. Compound Liner
Spray rubber based material onto the curl of the shells to improve
scalability.
4. Conversion Press
Make tabs and convert the shells into ends by combining with the tabs.
5. Palletizer

Stack the ends into paper bags and load them onto pallets.

Can end lines are relatively small and short when compared to can body
lines. There are no painting or coating processes and no bulky washing machines
and drying ovens. The speed of can end lines has increased dramatically in recent
years. A new type of shell press can produce 4,500 ends per minute and a new
type of conversion press can produce 1800 ends per minute for a three-lane
system and 2400 ends per minute for a four-lane system. Two conversion presses

are usually required for one shell press. Since there is no washer, decorator or

42

coating process, other equipment, such as a water treatment and distribution
system, a central coating storage system, a fuel storage system for dryers, an
exhaust treatment system, etc, is not required.

Can ends are packaged in a cylindrical paper bags which are stacked on
pallets. Ends are not bulky like can bodies and are relatively ﬂat. Therefore, the
transportation cost is relatively lower than for the can body. Because of these
differences, the can end lines are not necessarily located in the same plant as the

can body lines.

43

Aluminum metal for beverage cans

When aluminum cans were ﬁrst manufactured, by the impact extrusion
process, they were made of pure aluminum metal. However, the use of stronger
aluminum alloys in the drawing and ironing process has enabled manufacturers to
make cans lighter and less expensive. The aluminum alloys used for can bodies
are different than those used for the can ends. The alloy for tabs is also often

different from the can ends.

Aluminum alloys for can bodies

The aluminum metals currently used for can bodies are aluminum-
manganese alloys 3004 or 3104. The most common is 3004. The nominal

composition of these alloys is shown in Table 3-1.

Table 3-1 Nominal Composition of Aluminum Alloy for can body

 

 

 

 

 

 

 

 

Weight (%)
[ Element I Si Fe Cu Mn Mg Al I
| 3004 l 0.18 0.45 0.13 1.10 1.10 Remainin
| 3104 1 0.18 0.45 0.15 0.9 1.25 Remainin

 

Source: Reynolds Metals Company

Mg, Mn and Cu, the major strengthening elements, are controlled carefully

to achieve desired strength. However, the rate of strain caused by cold milling and

44
the heat treatments after cold milling or during cold milling are also important
factors determining strength.

The ﬁrst aluminum alloy used for beverage can bodies was 3004-O. It had
relatively low strength, so the industry switched to 3004-H32 which predominated
until the late 1960’s. In 1970's, there was another switch to a stronger alloy, 3004—
H19, which is still the most common aluminum alloy for beverage cans (3-1). The
symbols have the following meanings.

O : Annealed

The alloy loses the strength produced by strain hardening, so it is
weaker than a strain hardened alloy, such as a cold rolled alloy, but
is also easier to form.

H1 : Strain hardened

The alloy is made stronger by strain hardening thanwhen originally
caSt. The strain hardening is usually caused by cold rolling.

H3 : Strain hardened and stabilized
After strain hardening, a heat treatment is applied to stabilize the
alloy. This process increases the elongation and decreases strength
slightly.

The number after the H1 or H3, as in H32 and H19, shows strength.

The can body manufacturing line includes several process, such as the
base coater oven, decorator oven and inside spray oven, which take place at
temperatures about 200° C. The aluminum alloy receives a certain amount of
heat treatment in those processes which changes its mechanical properties.

Table 3-2 shows the mechanical properties of aluminum alloy both before and

after the heat treatments.

45

Table 3-2 Mechanical properties of aluminum alloys for can

bodies

 

As rolled Properties

After baking, 20 min at 204°C

 

 

 

 

 

 

 

 

 

 

Alloy Tensile Proof Elongation Tensile Proof Elongation
Strength Stress Strength Stress
(kg/mmz) (kg/mmz) (%) (kg/mmz) (kg/mmZ) (%)
3004 30.8 28.0 5.0 27.8 25.9 5.0
3104 31.5 28.1 5.0 29.4 26.6 5.0

 

Aluminum alloys for can ends

Source: Aluminum Company of America (3-2)

Aluminum alloys for can ends are strengthened by adding magnesium.

Other elements such as manganese and chromium are also added in minor

amounts to ﬁne tune strength and forrnability. The Table 3-3 shows the

guaranteed chemical composition of ALCOA (Aluminum Company of America)

aluminum end sheets.

 

46

Table 3-3 Guaranteed chemical composition of aluminum alloys

for can ends

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Alon Si Fe Cu Mn Mg Cr Zn Ti Other Al
5182 0.20 0.35 0.15 0.20~ 4.0~ 0.10 0.25 0.10 0.15 remaining
0.50 5.0
5082 0.20 0.35 0.15 0.15 6.0~ 0.15 0.25 0.10 0.15 remaining
5.0
5052 0.25 0.40 0.10 0.10 2.2~ 0.15~ 0.10 - 0.15 remaining
2.8 0.35

 

 

Composition in percent maximum unless shown as a range

Source: “Aluminum Easy Open End Manual”, ALCOA (3-3)

Alloy 5182-H19 is the most common selection for beverage can ends, but
some can manufactures use 5182-H42. Alloy 5082, developed for rivet-easy-Open
beer can ends, is composed of aluminum plus 5.5 percent magnesium. It used to
be common for beverage can ends, but the improved alloy 5182, which has higher
strength, has mostly replaced it. Another alloy, 5052, has lower strength than 5082
or 5182 but has good fon'nability. It is used to make ends for unpressurized cans
for oil and dry food products. Table 3-4 shows the mechanical properties of these

alloys.

Table 34 Mechanical Properties of aluminum alloys for can ends

47

 

 

 

 

 

 

 

 

Tensile Strength Proof Stress Elongation
(kg/mmz) (kg/mmz)
(%)
5182-H19 48.2 40.1 4
5082-H19 40.8 39.0 4
5052-H19 33.0 31.6 3

 

 

Source: “Aluminum Easy Open End Manual”, ALCOA (3-3)

The aluminum alloys used for tabs have properties similar to those used for
ends. The most popular aluminum alloy for tabs is 5082-H19, but 5042-H19 is also

used. The 5042-H19 has similar mechanical properties to those of 5082-H19.

Chapter 4

Lightweighting

To the ordinary consumer, two piece aluminum cans always look the
same. It is true that the basic dimensions, the body diameter and the shape, of
aluminum wns have not changed signiﬁcantly. However, can manufacturers have
been making efforts to change dimensions to reduce weights and costs ever since
the introduction of the aluminum can, over 30 years ago. Table 4-1 shows cost of
can bodies of some European can manufacturers.

The cost of the aluminum metal for the usual 12-ounce aluminum can
body is the highest fraction of the total production cost, 57.6 percent. The standard
can size in Europe is 330ml, a size close to the 12-ounce in the US. Therefore, it is
reasonable to asmme that the cost of aluminum metal for usual a 12-ounce US
can is around 58 percent. The aluminum metal cost of the can end for 12-ounce
beverage can is between 73 and 78 percent (4-2). Therefore, it is obvious that
reducing the weight of aluminum metal in a can in order to simultaneously reduce

costs has been a consistent goal for can manufacturers.

48

49
Table 4-1. Aluminum can body cost (2061211 330ml can)

 

 

 

 

 

 

 

 

Metal cost . 57.6 %

Production cost 42.4 %
Coating (inks, lacquers) 7.4 %
Other supplies (lubricant, washer chemicals, etc.) 5.7 %
Utilities (gas, water, electricity, etc.) 6.2 °/o
Labor 9.8 "/0
Others (taxes, equipment, building, maintenance, 13.3 %
etc.)

Total 100 %

 

 

 

 

 

Source: 'rhe Canner’ July 1995 (4-1)

Table 42. Aluminum and cost (Diameter 206)

Metal cost
Production cost

Labor
Overhead
Total

 

Example data from US companies (4-2)

To reduce costs, an manufacturers have developed technologies to
lighten cans. Programs to reduce costs have focused on reducing the weight of
metal for more than 30 years. It is not an exaggeration that the history of aluminum
can manufacturing is the history of the can light weighting.

Figure 4-1 shows the historical pattern of lightweighting aluminum cans.

Weights of both ends and bodies have been reduced. The weight of the end has

50
declined to 45 percent of the weight of the ﬁrst aluminum can end, and a can body

weighs 54 percent as much as it did in the early 1960's (4-3).

Can manufacturers have reduced the metal thickness for can bodies from
0.495mm (0.0195 inches) to 0.292mm (0.0115 inches). Net weight of the can body
fell from 17.79 (39 lbs/1000cans) to 11.39 (25 lbs/1000cans) (4- 4).

Research on lightweighting of can bodies and can ends has been pursued

separately and will be discussed separately in this paper.

51

 

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52

Can body lightweighting

Figure 4-2 shows the history of the can body weights over more than 30
years. Lightweighting progress in the ﬁrst several years, from 1962 to 1968, was
relatively rapid. This was the initial improvement of the can technologies in use
when aluminum beverage cans were ﬁrst manufactured. After the initial period, the
weight of the can body has been decreased gradually over time, reaching
25poundsl1000 mns in 1995. Recently, however, the weight has been decreased
further with a new technology, bottom reforming. By adding an extra forming
process in a can line after necking, the thickness of the bottom of the can has

been decreased further.

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54

Figure 4-3 shows the cross section of a typical aluminum two piece can body.
Can manufacturers have developed technologies to reduce the thickness of the can wall
including the neck thickness and the thickness of the can bottom. Weight reduction in

each of these areas uses signiﬁcantly different technologies.

Can wall thickness reduction

The aluminum sheet is ﬁrst drawn to shallow cups with a diameter larger than the
cans. The cups are drawn again to the same diameter as the cans. Then, the relatively
deep cups with the same diameters as the cans, are stretched. The thickness of the wall
of the cups is reduced to the clearance between two dies, the punch and ring-die. This
can wall forming process is called the “ironing” and the ring-die is called “ironing die”.
Usually, to get the wall thin enough, the ironing reduction is done three times on each
stroke of the punch, using three ring-dies in one tool pack as shown in Figure 3-4.

The can wall is further classiﬁed into two regions, the thin-wall, the middle portion

of the can side wall, and the thick-wall, the neck area.

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Thin-wall
The thickness of the thin wall, the middle portion of the side wall, is
important if the can is to have adequate strength to withstand the hoop stress
developed by the internal pressure from carbonated drinks. The hoop stress can

be calculated as shown in the following example,

(lntemal Pressure) x (Can Diameter)
2 x (Wall Thickness)

 

Hoop Stress =

Maximum lntemal Pressure: 6.3 kg/cm2
Can Diameter: 6.64 cm (2.61 inches)

Wall Thickness: 0.0102 cm (0.0040 inches)

The maximum internal pressure was assumed to be 6.3 kglcmz, the
standard inner pressure resistance required for the beverage can in the US. Thin
wall thickness in the US is approximately 0.102 mm.

In the preceding example, the hoop stress was estimated to be
20.5kglmm2. This stress is well below the tensile strength of the can wall, about 30
kg/mm2 (43 kpsi). However, the strength needed to support the axial load when
the can body is seamed together with the can end is usually greater than the
strength required to support the hoop stress. Therefore, the axial load is used ﬁrst

to determine the required thin-wall thickness.

57
The thin-wall of the standard 12-ounce aluminum can body has been

reduced from 0.165mm (0.0065 inches) in 1965 to 0.107mm (0.0042 inches) in
1990 and is expected to reduced to less than 0.100mm in a few years (4-5). There
are several concerns about the thinner thin-wall, such as dent and puncture
resistance during distribution and axial load resistance while being seamed with a
can end. The processability of the thin wall during the ironing process may also be
a problem when the thin wall is reduced even further. Tear-off, the breakage of the
side-wall of the can during the ironing process, will occur if the forming force

surpasses the strength of the wall.

Thick-wall (Neck Wall)

The thick-wall section, sometimes it called the neck wall, is made thicker
than the thin-wall section to allow for neck forming. The typical thick wall has been
reduced from 0.229mm (0.0090 inches) in 1965 to 0.157mm (0.0062 inches) in
1990 (4-3). In the same time period, neck diameters have been reduced from 211
(two and 11l16 inches, 68 mm) to 206 (two and 6/16 inches, 60mm). Generally it is
more difﬁcult to form the neck as the neck diameter reduction increases and the
neck thickness gets thinner. However, thinning the neck has proceeded steadily
despite the difﬁculty of neck forming to smaller diameters. Wrinkles are a primary
problem when forming the reduced necks with thin thick walls. Wrinkles, sometime
called pleats or creases, vary in size and shape. Some are just cosmetic defects

with no signiﬁcant effect on the performance of a can as a beverage container.

58

However, when there are wrinkles, the danger of imperfect seaming or splitting the

ﬂange of necks during the ﬁlling operation is a concern for can users.

Bottom thickness

Bottom thickness is important since the bottom of the can body must have
enough strength to withstand the inner pressure produced by carbon dioxide or
nitrogen, up to 6.3 kglcmz (90 psi) in the us. The bottom should be designed with
a shape and thickness which provide enough strength to resist the inner pressure.
Stability of the can while being conveyed in a can making line or in a ﬁlling line and
stackability are also important factors to be considered in the design. Bottom
thickness of a typical can has decreased from 0.495mm (0.0195 inches) in 1965 to
0.292mm (0.0115 inches) in 1994. Further reduction of the bottom thickness will
require an extra forming process, called bottom-reforming. As shown in Figure 4-4
and 4-5, this forming process reduces the stand radius of the can body and the
base diameter. Some lightweighting of the can body is currently done by this

process.

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61
Can End Lightweighting

Figure 4—6 shows an example of end lightweighting. The end weight has
fallen from 6.39 (13.8lbsl1000 ends) to 2.59 (5.6lbsl1000 ends) during the last
twenty years. The lightweighting rate has not been steady. There are two ways to
reduce the can and weight. One way is to reduce the thickness of the aluminum
sheet used for end making. The other is to reduce and diameter. As can been
seen in Figure 4-6, the reduction of and weight has been done gradually by the
reduction of stock gauge, the thickness of aluminum sheet, and drastically by
diameter changes in 1977, 1992 and 1993. The increase in the weight in 1974 was
due to the introduction of the “stay on tab” which replaced the “ring pull tab” to
solve the tab littering problem.

Usually the minimum internal pressure which can buckle the can end is
required to be more than 6.3kglcm2 (90 psi). Development of a new type or shape
of and shell may lead to a reduction of the metal thickness and weight. But, the
reduction of end diameters produces greater pressure resistance at the same
metal thickness. When the end diameter is reduced, the metal thickness can also
be reduced even with a similar shape.

One of the reasons that aluminum cans dominate the large US beverage
packaging market is their relatively low cost. The decrease in aluminum metal
ingot prices contributed to the success of the aluminum can industry until 1993.
As can been seen in Table 4-2, metal cost is as much as 78.2 percent of the total
end cost for 206 diameter ends. Of course, the percentage will ﬂuctuate in

response to the prices of aluminum metal and other raw materials. The metal cost

62
ratio against the total cost of a 204 or 202 end, both of which were developed to

reduce can costs, will become relatively lower than for the 206 end because the
cost of metal decreases but the capital investment including end making

machinery will be required and other costs may remain the same.

 

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Chapter 5
Recycling

The aluminum can market for beverages in the US has grown steadily since
the cans were introduced in the 1960's. Light weight and stackability helped the
aluminum can quickly displace glass bottles and other containers in both the soft
drink and bear markets. But, one of the most signiﬁcant characteristics of the
aluminum can is its recyclability compared to other packaging materials. In the US,
aluminum beverage cans are considered to be environmentally friendly. This is
one reason that aluminum cans for beverages were accepted so quickly.
According to the Aluminum Association, 106,014 million aluminum cans were
shipped in the US In 1994, and the recycling rate reached 65.4 percent(5-1).

Aluminum cans must be reasonably cheap to be accepted as beverage
containers, even though the raw aluminum is not inexpensive. As shown in the
cost breakdown for aluminum cans, Tables 4-1 and 4-2 in Chapter 4, 57.6 percent
of the total production cost of the aluminum can body and 78.6 percent of that of
aluminum can end is the direct cost of the aluminum metal (5-2).

Since 1994, the price of aluminum has been increasing because of the
decreased shipments of aluminum ingots by Russia. As a consequence, aluminum
can recycling is attracting attention, not only from the environmental viewpoint,
but also from the business viewpoint, bewuse recycling aluminum used beverage
cans (UBCs) is proﬁtable. In 1994, the industry paid $1.15 billion for the 64.7 billion
aluminum UBC’s which were recovered for remelt (5-3).

64

65

Packaging materials in the municipal solid waste

Since the late 1980's, information and environmental events have raised
public awareness of the municipal solid waste crisis. In 1989, the Environmental
Protection Agency (EPA) formed a group to analyze the solid waste problem and
propose solutions. The experts developed an “Agenda for Action” to solve the
garbage problem(5-4). One program was designed to minimize the volume of solid
waste generated from packaging because approximately one-third of all landﬁlled
Municipal Solid Waste originates from packaging (5-4). EPA statistics on major
categories of MSW are shown in Figure 5-1. In 1993, 207 million tons of municipal
solid waste were generated in the United State and the recovery of materials for
recycling and composting reached an estimated 22 percent (5-5). The recovery
rates in 1993 for each component of municipal solid waste are shown in Figure 5-
2. The recovery rates of metal packaging, both aluminum and steel, are
signiﬁcantly higher than for other package materials. In 1993, the aluminum
packaging recovery rate was 53.0 percent overall and 59.5 percent for aluminum
cans (5-5). The recycling of aluminum cans has been good example of the
beneﬁts of recycling in general and has given the public a positive impression

about aluminum cans for beverages.

66

     

Food and
Other Wastes Containers
8%
and
Durable Packaging
Goods 33%

14%

Yard Waste
1 8%

Non-durables
27%

Figure 5-1 Sources of Landﬁlled Waste

Source: Characterization of the Municipal Solid Waste Stream, 1992
Update, US, EPA, October 1992 (5-13)

67

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68

Recovery of aluminum metal from municipal solid waste

Aluminum metal recovered from municipal solid waste (MSW) is mainly
from packaging, beverage cans for soft drinks or beer. The breakdown of

aluminum metal from MSW is shown in Table 5-1.

Table 5-1 Aluminum Products in MSW, 1993

 

 

 

 

 

 

 

 

 

 

 

 

Durable Nondurable Containers and Packaging
Goods Goods
Beverage Food and Foil and
Cans Other Closures
Cans
Generation 810 180 1610 40 330
(1000tons)
Recovery Neg Neg 1020 Neg 30
(1000tons)
Recovery Neg Neg 63.4 Neg 9.1
(%)
Neg. = negligible

Source: Franklin Associates, Ltd.

As shown in Table 5-1, the biggest aluminum product in MSW is aluminum
cans for beverages. Most of the recovered aluminum comes from UBC’s. The
recovery rate was 63.4 "/0 in 1993 and 65.4 % in 1994, the highest recovery rate
for common packaging materials (5-5). The primary reason for the high recovery
rate is the value of the UBC. However, the size of the market for aluminum UBC’s

also has a positive inﬂuence on the recycling rate.

 

69

Aluminum used beverage can recycling business
The market for aluminum beverage cans is substantial and the value of
UBC’s is relatively high, so some companies are collecting UBC’s as a business.
Most of these companies are subsidiaries of major aluminum, aluminum can, or
beverage companies. They have understood the importance of recycling since the
start of the aluminum beverage can business.
The following ﬁve companies controlled about 80 percent of UBCs
collections in US in 1994 (5-4).
oAnheuser-Bush Recycling Corp.
Subsidiary of Anheuser-Bush Inc., largest beer company in the world
oAlcoa Recycling Co.
Subsidiary of Alcoa, largest aluminum company in the world
oReynolds Aluminum Recycling Co.
Subsidiary of Reynolds Metals Co., third largest aluminum company
in the world and world’s third largest aluminum can company,
American National Can Company
Second largest aluminum can company in the world
oGolden Aluminum Company

Subsidiary of Coors beer company

In 1994, the industry paid approximately $1.15 billion to recyclers to get

back aluminum UBCs (5-10). The money was injected back into local economies

70

to beneﬁt individuals, municipalities, schools, churches, scout troops and non-
proﬁt organizations (5-6). Most of the used aluminum cans are returned through
the industry’s market-driven collection infrastructure, which includes thousands of
buy-back centers nationwide. About 60 percent of the total UBCs collected come
from buy-back centers (5-7).

Energy saving is a main beneﬁt of recycling aluminum. Recycling aluminum
saves about 95 percent of the energy needed to make the primary metal from I
bauxite. It takes more than 15,000 kWh to produce one metric ton of primary
aluminum metal compared with less than 1,800 kWh for recycled aluminum (5-8).
Aluminum recycling also requires much less capital investment than production of
the metal from primary sources. The processing cost of UBCs is about $143 per
ton (6.5 cents/pound) (5-9), whereas the price virgin aluminum metal was $1100 ~
1980 per ton (50 - 90 cents/pound) last year as shown in Figure 5-3. Processing

costs vs. prices of recycled materials are shown in Table 5-2.

71

Table 5-2 Processing costs vs. prices of recycled materials

 

 

 

 

 

 

 

 

 

 

Processing Cost Selling Price Ratio of
lDollarsper Tons) (Dollars per Tons) Price and Cost

Newspaper 34 0~25 0~0.74
Corrugated Board 43 8~30 0.19~0.70
Steel Cans 68 65~90 0.96~1.32
Clear Glass 73 40~45 0.55~0.62
Amber Glass 112 20~35 0.18~0.31
GreenGlass 87 4~12 o.05~0.14
PET 184 35~195 0.19~1.06
HDPE 188 35~240 0.19~1.28
Aluminum Cans 143 500~800 3.50~5.60

 

 

 

 

 

 

Source: Average process cost: National Solid Wastes Management Assn.
Recycled materials prices, East Central region, May 18, 1993: Recycling
Times, Packaging Digest, June 1993 (5-15)

For these reasons the industry demand for UBCs as a source of raw
material for making new cans has been stable and strong, especially since 1994,

when the price of aluminum began to rise sharply.

Aluminum metal price and recycling

The aluminum metal price affects aluminum can prices directly. Figure 5-3
shows aluminum metal prices and aluminum UBC prices. As can be seen, the
price of aluminum metal is unstable and the price of U805 has been changing in
relation to the LME (London Metal Exchange) prices for aluminum. This ﬂuctuation
in aluminum metal price is due to the relationship between demand and supply.

Prices were relatively low until the end of 1993 because of the high rate of export

72

of aluminum ingots to the world market from Russia. In January 1994, when
aluminum industries of the West signed a “Memorandum of Understanding” with
Russian aluminum suppliers(5-11), aluminum prices begins to rise. After the fall of
the Soviet Union, Russia had steadily increased the amount of aluminum ingots
that the nation sold on the world market. In the 1980’s, Russia was exporting
about 200,000 tons (441 million pounds) of aluminum ingots per year, but had
raised its annual aluminum ingot export to 2,000,000 tons (4410 million pounds) in
1993. The “Memorandum of Understanding” requires export of 500,000 tons (1100
million pounds) per year (5-11). The world wide aluminum surplus quickly turned
into an aluminum shortage and the price of aluminum rose almost 60 percent in
less than 10 months. Negotiations about aluminum can prices began between
suppliers and purchasers.

According to “Beverage World” (5-1 1), it is projected that as of year-end
1995, the cost of aluminum cans will stand at $70.58 per 1000 - versus $70.68 for
PET bottles and $65.66 for steel cans due to the aluminum metal price of $1760
per ton (80 cents per pound) (5-11). This price for aluminum cans is an increase of
25 percent compared to $56.56 per 1000 in 1994(5-12), and is the ﬁrst signiﬁcant
increase in beverage can costs in the last 10 years. The industry’s strong demand
for UBCs and the high recovery rate of UBCs in 1994 resulted from this economic

situation.

73

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74

Recycled content of UBC in new cans

According to the Aluminum Association and Can Manufacturers Institute,
UBC recovery in 1994 was 807,000 tons (1.78 billion pounds) and 1492,000 tons
(3.29 billion pounds) of cans were shipped (5-10 ). From these numbers the UBC
content can be calculated to be 54.1 percent, and this number is used in some
papers as an average UBC content in an aluminum can. However, recycled
aluminum metal from UBCs is usually not used for can ends (lids) but only for can
bodies. The reason is that different aluminum alloys are used for the can ends and
the can bodies, as explained in Chapter 3. Components of an example of each
type of alloy are shown in Table 5-3. There may be small differences in the amount
of each element added to aluminum from company to company, but aluminum

alloy 3004 is most commonly used for can bodies and 5182 for can ends.

Table 5-3 Aluminum alloy components list (weight %)

 

Alloy Si Fe Cu Mn Mg Cr Zn Ti Al
No.
Body 3004 0.28 0.48 0.23 1.00 1.1 0.02 0.05 0.03 rem.
End 5182 0.12 0.24 0.04 0.29 4.6 0.03 0.02 0.01 rem.

rem. = remaining

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Source: Mitsubishi Aluminum Co.

The important components of 3004 (for can bodies) are manganese and
magnesium. Manganese improves processability while ironing the can wall (the

ironing process is to make the metal wall thin using a male die and female dies

75

after the draw and redraw process, see Figure 3—10 ). The ironing process is not
used for making can ends, so little manganese is needed in 5182. Magnesium
increases the alloy strength which is important for resistance of the can against the
internal pressure. More magnesium is added to the alloy for the can ends to
increase strength.

Assuming that the average weight of the can end and the can body for 12
oz aluminum cans is 4.04 g (8.9lbsl1000) can ends and 11.7 g (25.8lbsl1000) can
bodies, as shown in Chapter 4, the components of the recycled aluminum metal

from UBCs can be calculated, as shown in Table 5-4.

Table 5-4 Calculated components of recycled aluminum from
UBCs

 

[Component [ Si Fe Cu Mn Wig Cr Zn Ti Al I
LCalculated % l 0.24 0.42 0.18 0.82 2.00 0.02 0.04 0.02 rem.|

rem. = remaining

 

 

 

 

 

 

 

 

 

 

By comparing the information in Tables 5-3 and 54, it can be seen that the
alloy components must be adjusted before the recycled aluminum can be used to
make new cans. For the can body alloy, virgin aluminum is added to reduce the
fraction of magnesium. The average magnesium content for can bodies is about
1.00 - 1.10 %. If the Mg content is higher, the tear-off rate (tearing of the can body)
during the ironing process may rise, causing production efficiency to decrease.

The maximum allowable magnesium content is approximately 1.10 percent.

76

Therefore, the theoretical maximum content of UBCs for a can body alloy is 55

percent due to the content of magnesium. For a can end alloy, the maximum is 21

percent due to other component such as Cu.

However, the actual percentages of the various components are often

different from the theoretical percentages because of oxidation or other reactions

with contaminants. Magnesium, especially, tends to be oxidized easily and some

of its oxides are eliminated when the UBC’s are melted. The actual components of

recycled aluminum from UBCs are shown in Table 5-5.

Table 5-5 Example of component of recycled aluminum metal

 

 

from UBCs
I component I Si Fe Cu Mn ML Cr Zn Ti Al j
[Calculated % | 0.27 0.47 0.22 0.97 1.35 0.02 0.05 0.03 rem. |

 

 

 

 

 

 

 

 

 

rem. = remaining

Source: from Mitsubishi Aluminum Co.

The estimated maximum content of UBCs for can body alloy is 81 percent

based on the preceding data. If the recycled aluminum is melted twice orif the

melted time is longer than is usual for the process, the content of magnesium will

be lower than 1.35 % because of increased oxidation. In this case, the maximum

possible content of UBCs will increase due to reduction of magnesium. However,

melting twice or using longer melting time will decrease production efﬁciency and

increase the cost.

77

The maximum content of UBC for the can end alloy is still about 20 percent
because the amount of Si, Cu, Fe and Zn in 5182 alloy should be low. Therefore, it
is difﬁcult economically to use UBCs for the can end alloy. If the content of certain
components is higher than the speciﬁcation, quality problems can result.

According to Reynolds Aluminum Recycling Company, “No companies are
using UBCs for can end alloy, 5182". They are mainly using UBCs for can body
alloys 3004 or 3104. Some companies are researching or testing new alloys for A

can ends which will allow greater use of UBCs.

Aluminum can recycling problems to be solved

Aluminum UBC recycling is business-oriented because the UBC has
enough value to justify recyling and because the beverage can market is large.
The recent rise of aluminum metal prices provides an incentive to attempt to
increase the recovery rate of aluminum UBCs. An increase in the recovery rate
improve the competitiveness of the aluminum cans vs. PET bottles or glass
bottles. But, taking into account the strong demand for UBCs and the public
understanding of the importance of recycling used packaging to avoid the future
municipal solid waste crisis, the recovery rate of Aluminum UBCs, 65.4 %, should
already be much higher. A more efﬁcient or broader system including state and
federal governments, communities, and industries will be needed to increase the
recovery of U803.

The aluminum companies need to develop new alloys for can ends which

can be made from UBCs to increase UBCs content in aluminum cans. If the UBC

78

recovery rate increases, the companies need to be prepared to use UBCs for can

ends. The ends should be less expensive as a result.

Chapter 6

Further can weight reduction

Price competitiveness

The price of aluminum is the most important factor in the competition
between aluminum cans and glass bottles, plastic bottles (PET) and steel cans.
Aluminum prices will have to be stabilized for aluminum cans to continue to be
competitive. If the rate of increase in aluminum can prices is greater than the
equivalent rate of increase for competing PET containers, aluminum will inevitably
lose market share.

This chapter focuses on possible future cost reduction of aluminum cans.
Three cost categories will be examined: 1) reduction of the amount of aluminum
metal in cans, 2) aluminum metal price fluctuations, and 3) other costs including

coating, production efﬁciency, and labor.

79

80

Can weight reduction

Since the introduction of aluminum cans, weight reduction has been the
primary approach that has been used to reduce costs. Weight reduction will
probably continue to be the primary method for the next several years. When
evaluating the potential for additional reduction in the weight of aluminum cans,
the can end and the can body must both be considered.

The can body and the weight of the can body can be segmented into three
sections as deﬁned in Figure 6-1: 1) neck, 2) thin wall, and 3) bottom. The can end
weight can also classiﬁed into two parts: 1) shell weight and 2) tab weight. Figure
6-2 shows the parts of a can end. In this Chapter, each part is discussed
separately.

To reduce the weight of a can, the dimensions of some part(s) of the can
must be reduced. Each dimensional change also affects certain properties or
characteristics of the can. Each change of dimension requires the consideration of
one or more factors related to the properties or the processability of the can.
Table 6-3 shows the outline of the relationships among these factors. Some
factors are related to other factors and two or more may have to be considered in

combination.

81

 

 

 

 

 

Can ' Crosssection
before Necking

 

Figure 6-1 Can Body Classiﬁcation

 

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Thin Wall Area

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Can body weight

The can body weight can be divided into three parts, neck weight, thin wall
weight and bottom weight, as deﬁned in Figure 6-1. The neck weight is deﬁned as
the weight of the upper part of the can wall where the thickness is usually constant
before the neck forming process. After necking, the thickness will increase
according to the amount of the reduction of the diameter. The thin wall weight is
deﬁned as the weight of the middle and thinnest part of the wall, including the
thickness transition zones to the neck and the bottom. Bottom weight is deﬁned as
the weight of the bottom part of the can where no ironing forming takes place.
Usually the weights of each of these three parts can be designed individually,
independent of each other except for the lengths of the neck wall and the thin wall
which are a function of the can volume.

The weight of each area of the can is not likely to be reduced at the same
rate. Some part of the can may be reduced signiﬁcantly, while the others are not
changed as much. Figure 6-4 illustrates a can cross section based on the data in
Table 6-2, Sample A, which is a recent typical US aluminum can for beverages.
The length and thickness data were measured by a “Can Body Measuring
Machine” at the Mitsubishi Maten'als Corp. The neck thickness and the neck length
were obtained before neck forming. These data an be used approximately and as
a reference. Each can manufacturer has different speciﬁcations, but the errors
which result by using these typical speciﬁcations for current aluminum beverage
inns in the US an be regarded as small. Therefore, in this chapter, these data

are used to analyze can body lightweighting.

85

  

 

 

 

 

 

 

 

 

/////////////////////////.«’// /////////// M/ﬂ \\\\\\\\\\\\\\\\\\

Con Crosssection
before Necking

 

Con Diameter : 6.61 cm

 

 

Density of Aluminum Alloy : 2.729/cm3

 

’/
W// '/////////////////////////////////////////////

 

 

Figure 64 Typical can body dimension, 202/21 1 12-ounce can

86
Using the data in Figure 6-4, the weight of each part of the can body can

be calculated as follows.
Neck Weight

2.11 X6.61nX0.0160X2.72 = 1.959 (0.00430 lbs)

Thin Wall Weight

0.6 x (0.0160+0.0104)/2 x 6.611: x 2.72 = 0.459 (0.00099 lbs)
7.8 X00104 X6611: x2.72 = 4.589 (0.0101 lbs)
1 x (0.299+0.0104)12 X6.611t x272 = 1.149 (0.00251 lbs)

Total = 6.179 (0.0136 lbs)

Bottom weight can be approximated by using the inner diameter of the
redraw die which is close to the diameter of the aluminum metal to be formed into
the bottom. Strictly speaking, some plastic ﬂow will occur from the outside into the
bottom area. The actual thickness before forming is 0.002 - 0.003mm greater than
the center of the bottom. Therefore, the actual weight will be slightly more than the
estimate. Using the redraw inner diameter (can diameter + ironing reduction x 2),
the approximate bottom weight can be calculated as follows.

Bottom weight

0.0299 x 1r{(6.61l21I-(0.0299-0.0104)}2 x 2.72 = 2.849 (0.00129 lbs)

Therefore, the total can weight is estimated to 10.969 (0.0242 lbs) (1.959
+ 6.179 + 2.849), a little lighter than the actual weight, 11.459 (0.0252 lbs) (6-2).
The difference of 0.499 (0.00108 lbs) is probably the result of under estimating the

can bottom weight. If the weight estimates of the neck and thin wall are accepted

87
as calculated, the bottom weight would be 3.339 (0.00734 lbs) (11.459 - 1.959 -

6.179).
Figure 6-5 shows the weight break down for typical aluminum beverage
cans in the US. The end shell weight and the tab weight in Figure 6—5 are from the

same company (6-2).

88

Aluminum can weight, 202/211,12-ounce

Tab
2%

Shell 202

Bottom

 

Thin Wall
43%

Figure 6-5 Aluminum can weight break down, 202/211 12-ounce

Because of the larger area of the side wall, the thin wall is the heaviest
part of an aluminum can. The wall of an aluminum beverage can feels very thin,
giving an impression that reduction of the wall would be nearly impossible.
However, as seen in the preceding discussion, further reduction of the thin wall
weight is essential to reduce cost.

The second heaviest section is the bottom. Reduction is also desirable in

the weight of the bottom. A new bottom shape will be required. There is also

89
another signiﬁcant problem with the bottom shape of 202/211 cans: stability when

cans are stacked on top of one another.
The example data is for a 202/211, 12-ounce can, indicating that the
weight of the end has already reduced from that of 206 or 204 diameter ends.

Further reduction of the end diameter is being researched by can manufacturers.

The possibilities of further lightweighting of each part are discussed in the

next section.

90

Thin wall thickness and weight

The thin wall is formed by an ironing process which reduces the thickness
of the can wall by squeezing it through the gap between a punch and ring-die.
The ironing process has enabled manufacturers to make the can wall thin and less
expensive by reducing its weight. The ironing process, shown in Figures 3—9 and
3-10, is used on beverage cans but not for making food wns. The thin wall is
much thinner than the original aluminum sheet The thinness of the wall is the
reason that a positive inner pressure is always required when aluminum beverage
cans are used. The cans simply do not have the axial strength required for
stacking unless they are pressurized.

The percentage of reduction from ironing is illustrated below.

Thickness before Ironing - Finish Thickness
Thickness before Ironing

 

Reduction (%) = x 100

A similar equation can be used to calculate other reductions. For example,
the ironing reduction of a can which has 0.103mm (0.0041 inches) thin wall
thickness made from 0.290mm (0.0114 inches) thickness aluminum sheet will be
64.5 percent. Immediately before ironing, the can wall is thicker than the original
aluminum sheet due to drawing. Therefore, the real ironing reduction will be a
little greater than 64.5 percent.

Generally, the maximum thickness reduction is about 40 percent in one
ironing pass. Therefore, two or more passes are required to make a can body.

Current practice is to use three ironing passes for good can quality and good

91

operating efﬁciency of the can body press machine. To eliminate problems, three
ironing dies are mounted in a tool pack, also called a die-set, to make the can wall.

A tool pack with three ironing dies is longer than one with two dies.

There needs to be enough distance between dies to avoid two ironing dies
working on the material at the same time. A shorter tool pack can be operated at a
higher press speed, directly improving production efﬁciency. A longer ironing press
stroke, which accommodates a longer tool pack, decreases the speed of the
press. In the 1960's, presses which could operate at 100 strokes per minute were
rather fast. Current ironing presses can be operated at more than 400 strokes per
minute. Some manufacturers tried a shorter tool pack with only two ironing ring-
dies to increase the press speed, but the tear-off rate increased and the life of the
ring-dies decreased.

The following items are important factors to improve the ironing process.

a. Tool geometry and quality

b. Lubrication

c. Metal properties and quality

d. Ironing press quality (Tool Alignment)

Technologies to control these factors have been developed by can
manufacturers. Metal properties, manipulated by aluminum companies, have
affected both the production efﬁciency of the can line and can performance.
Future changes could be made to increase the strength of the aluminum alloys

and give higher strength to the cans but the changes might also decrease

92

forrnability, which would lower production efﬁciency and could conceivably make

the ironing process impossible.

Reduction of the thin wall

The thin wall has been reduced signiﬁcantly since the introduction of

aluminum can. The history the thin wall thickness is shown in the Table 6-1.

Table 6-1 Thin wall thickness history

 

 

 

 

IYear J1965 1970 1975 1980 1985 1990 1995 1
Thickness 10.165 0.145 0.135 0.126 0.114 0.107 0.102
(mm)

 

 

 

 

 

Source: Aluminum Company of America (G.L. Smith, “Barriers to Lightweighting

of Aluminum D&I Beverage Can”), (6-1)

During these 30 years, the thin wall was reduced from 0.165mm (0.0065

inches) to 0.102mm (0.0040 inches), a 38 percent decrease. The critical factor

limiting the reduction of the thin wall thickness is the axial strength of the cans,

referred to as “column strength”. Column strength is required when the can body is

seamed together with a can end after being ﬁlled. Some axial loading is required to

get proper double seam dimensions during the seaming operation.

Dimensions and other data about cans made by companies in the US and

Europe are shown in Table 6-2 (6-2). Figure 6-6 shows the relationship of column

strength and thin wall thickness. The data are from cans made by three US

93

companies refened to as A, B, and C. It can be seen that the axial column strength
of can bodies is approximately proportional to the thin wall thickness.

The column strength, axial strength of the can wall is theoretically a
function of the thin wall thickness and the compression strength of the aluminum
alloy.

Column Strength = F (t, c, f)

t = thin wall thickness
3 = compression strength of aluminum
f = shape factor

The aluminum alloys used for the can bodies are all similar, usually 3004-
H19 or 3104-H19, aluminum-manganese alloy and the hardness data of these can
bodies in Table 6-2 doesn’t'show many differences. The shape factors are also
assumed to be very similar to each other. Therefore, the column strength of the
can bodies can be assumed as a function of the thin wall thickness.

Column Strength = F (t)

According to the data of the Figure 6-6, the relationship will be as following,

Column Strength (kg) = 1257 >< Thin wall thickness (mm) + 3.3 -—(A)

(Column Strength (lb) = 70400 X Thin wall thickness (inch) + 7.28)

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96

Each data value in Figure 6-6 is the average of data for three cans in the
same lot. The limitation to the reduction of the thin wall has been the column
strength of the can body instead of resistance to rupture during distribution or
internal pressure of the product. Column strength is required dun'ng distribution
and also for the for ability to withstand the load placed on the can when the an
body and the can end are seamed together. The rapid rise of the lifter assembly
combined with inertia creates high peak loads on the cans which are intensiﬁed by
rapid acceleiation, especially during high speed seaming when processing at a
high speed, such as 2000 cans per minute.

Column strength standards for aluminum beverage cans in the US are
between 90.7kg ~ 136.1kg (200 and 300 pounds) where peak load is expected to
be about 68.0kg (150 pounds) (6-3). The peak load exerted during seaming
depends on the adjustment of springs which prevent the cans from rotating
against the lifter pads to get satisfactory double seam dimensions. To soften the
peak loads, the technologies, including cam proﬁle, which control the lifter
movement have been improved. Recently, a new type of seamer, which reduces
the peak load to 27 kg (60 pounds) from the conventional load of 68 kg (150
pounds), has been developed (6-3). To compensate for the possibility that some
cans have defects or ﬂaws and to guarantee an effective seaming operation at
high speed, the speciﬁmtion of the column strength should be higher than the
peak load exerted by the seamer.

If the new seamers with low peak load allow cans to be manufactured

which have lower column strength standards, further reduction of the thin wall will

97
be possible. Based on the equation shown in Figure 6-6, the thin wall required for

36.3kg (80 pounds) of column strength is 0.026mm (0.00102 inches) and that for
54.4kg (120 pounds) of column strength is 0.041mm (0.00161 inches). Even if the
expected peak load continues to be 68 kg (150 pounds) the thin wall requirement
will be 0.051mm (0.002 inches), much thinner than the walls on current cans.

Die-necking is another operation which requires that the can have
adequate column strength. The collapse mode of the can wall due to an axial load
is bending toward the inside of the can in an area of the wall. During die-necking, 2
- 3 kglcmz (28.6 ~ 42.9 psi) of air pressure is applied to the inside of the can body
to increase the ability to support an axial load. The die-necking load ranges from
45kg ~ 1kg (100 to 200 pounds) (6-8), signiﬁcantly less than the column strength
with applying inner pressure. Therefore, necking loads don’t need to be
considered when the thin wall column strength is considered. However, the outer
nose wall of the bottom of the can body must have adequate resistance to the
necking loads to avoid damage.

After the new type of seamer comes into common use, further reduction of
the thin wall will depend on other factors, such as hoop stress resistance to the

inner pressure of the products or rupture resistance dun'ng distribution.

Resistance to hoop stress

The hoop stress can be calculated as shown below:

(lntemal Pressure) x (Can Diameter)
2 x (Wall Thickness)

 

Hoop Stress =

98
The internal pressure depends on the type of product and the

temperature. The inner pressure resistance standard in the US is 6.3kglcm2', so a
can should never be pressurized beyond that level. A standard 12—ounce can is
about 66.0mm in diameter. The maximum hoop stress, therefore, is a direct

function of the wall thickness and is calculated as shown below.

2.079

Hoo Stress k [mm2 =
p ( g ) Wall Thickness (mm)

 

Figure 6-7 shows the relation ship between the hoop stress and the thin

wall thickness.

Thin wall thickness vs. Hoop stress

h
01

 

 

 

 

 

m)
we
mo

)—

 

 

(a)
0

———--1r--—
p
b
_ sh—ydf %
.
,
p
b
p
___E_..__ _ _.

 

 

N
01

 

 

 

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.s
O

 

Hoop stress (kg/m
N
O

01

 

 

 

l
l
;
j

 

 

 

 

 

o A A A .
0.040 0.060 0.080 0.100 0.120 0.140 0.160

Thin wall thickness (mm)

Figure 6-7 Maximum hoop stress (at 6.3 kglcmz) vs. Thin wall
thickness

99

If the tensile strength of the aluminum can body metal is given, the
required wall thickness can be calculated. The tensile strength of the common
aluminum metal used for can bodies in the US is 28.1kglmm2 ~ 30.6kg/mm2 (40.1
kpsi ~43.7 kpsi) (6-4).

The tensile stress can also be estimated from the hardness of the metal if
data is available for mlibration of the relationship between the hardness and
tensile strength. Figure 6—8 shows the relationship for a particular aluminum alloy,
3004-H19. Usually, the tensile strength is not necessarily related to hardness.
However, when working with aluminum can metals, the compositions, rolling
conditions and heat treatments are all similar. Therefore, the tensile strength can
be estimated from hardness which is easier to measure than tensile tests using

real can body walls.

100

Tensile strength vs. Hardness
y = 0.203x + 9.74

 

31.5 1 s

30.5 ! ‘ /

30.0 ‘

l
29.5 i/l/
29.0

28.5

 

 

 

 

 

 

 

 

Ttensile Strength, kg/mm2

 

 

 

 

 

 

 

 

94 96 98 100 102 104 106
Hardness, Hv

Figure 6-8 Tensile strength and hardness, 3004-H19

Source: Mitsubishi Materials Corporation

The tensile strength of aluminum sheet before forming can be estimated
from the graph if the hardness is known. The strength of the metal changes during
forming because of work hardening and the thermal effects of the can
manufacturing line. Therefore, compensation should be considered when these
data are used. Figure 6-9 shows the effect of work hardening of the aluminum in a
can body due to ironing. Samples A and D are common can body alloys.

Samples B and C are special alloys developed to reduce the work hardening rate

and give better neck formability. The thin wall and thick wall are harder than the

101

bottom, approximately as hard as the aluminum sheet before forming. The thin

wall is harder than the thick wall because it is ironed more than the thick wall.

Hardness of aluminum can after D&I forming

 

 

 

 

 

 

 

 

 

 

 

 

 

 

125 —o—A
120 -'-B
115 ' C
E [no-D
a" 110
§
2 105
a
I 100
95
90

Bottom Thin Wall Thick Wall
Area of Aluminum Can

Figure 6-9 Work hardening of can body

Source: Mitsubishi Materials Corporation

After forming, the can body is moved to other processes: washing, drying,
printing, drying, inside coating, drying and neck forming. The three drying ovens
give the can body a slight heat treatment. The temperatures of the ovens are
controlled to the minimum level for drying or curing, usually lower than 200°C, but
high enough to affect material properties. Figure 6-10 shows the hardness after

baking and drying of each section of cans made of different materials.

102

Hardness of aluminum can
before neck forming

 

 

 

 

 

 

 

 

 

 

 

 

 

125 hr),
120 _ .- _ B

> 115 " C
I. ”no,
a 110
8
f, 105
O
I 100

95

90 1 #1

Bottom Thin Wall Thick Wall
Area of Can

Figure 6-10 Can body hardness after baking and before necking

Source: Mitsubishi Materials Corporation

The materials (A, B, C, and D) are the same as shown in Figure 68.
From the graph, it can be seen that the thin wall hardness is 5 ~ 10 percent higher
than the hardness of the bottom, about 10 percent for the usual can body materials
and about 5 percent for the low work harden materials.

The tensile strength plotted in the graph was measured along the rolling
direction. The anisotropy of the aluminum alloy also has to be considered. The
tensile strength in the rolling direction is higher than in the perpendicular direction.
The difference varies from alloy to alloy, but is usually less than 10 percent for

aluminum an body alloys.

103

The tensile strength in rolling direction of the material at the bottom of the
can body can be assumed to be approximately equal to the strength in cross
direction of the wall which resists the internal pressure. The tensile strength of the
bottom of can bodies can be approximately calculated with the following equation,

based on Figure 6-7.

Tensile strength (kg/mmz) = 0.203 x Hardness (Hv) + 9.74
(Tensile strength (psi) = 290 X Hardness (Hv) + 13900)

The average hardness of the bottoms of cans in Table 6-2 is 98.9 (Hv),
the tensile strength can be calculated to be 29.8 kg] mm2 (42.6 kpsi) and the thin
wall thickness can be calculated to be 0.070 mm (0.00276 inches). Therefore, the
theoretical minimum thin wall thickness is 0.070mm (0.00276 inches) to resist the
internal pressure of 6.3 kglcm2(90 psi).

A factor which must be taken into consideration, in addition to the axial
load resistance during seaming and the resistance to the inner pressure, is
damage during distribution. Ruptures or holes caused when the cans impact on
sharp objects are the most probable types of damage that can be directly related
to thin walls. Damage during distribution is highly dependent on the total
packaging system including the corrugated box or tray, secondary packaging (Hi-
cone rings), shrink ﬁlm and pallet, and the method of shipping or transportation.
Bemuse of the number of variables, it is difﬁcult to predict the level of damage

analytically. Testing is almost always required.

104
It can be predicted that further reduction of the thin wall will be possible

after introducing the new seamer which places less axial load on the can during
seaming. The factor which will limit the reduction will be burst resistance including
resistance to pin hole or rupture. On this basis, it may be possible to reduce the
thin wall to 0.090 mm (0.00354 inches) or less.

Figure 6-11 shows the thin wall weight as a function of wall thickness,
based on the can dimensions in Figure 6-4. The thick wall and thickness of each

transition area are assumed to be proportional to the thin wall.

Thin wall weight vs. Thin wall thickness

 

 

 

 

 

 

 

6.5

/
6.0 /
5.5 l //

 

 

 

 

i i.
i /1/ 1 4

 

99:5.
0100'!

 

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Thin Wall Weight (g)
01
O

 

 

 

 

 

 

1
1
i
i
l
1

 

l . l

 

3.0
0.065 0.075 0.085 0.095 0.105 0.115

Thin Wall Thickness (mm)

Figure 6-11 Thin wall weight vs. thin wall thickness

105

Neck wall weight and thick wall thickness

The neck wall, also called the thick wall, is the upper part of the can wall
where the thickness is greater than the thin wall. The thick wall is required to
achieve easy of reduction of the neck diameter from 211 to 206, 204 or 202. The
neck wall extends from the top of the can body to the beginning of the neck curve.
Therefore, the lightweighting of the thick wall depends on the neck forming
technology.

Before neck forming, the thickness of the neck wall is constant along its
length. After necking, the thickness is increased proportional to the reduction in
diameter. Table 6-3 shows an example of this increase in thickness caused by
neck reduction. In 1965, the thick wall was around 0.229mm (0.0090 inches) (6-5).
It has dropped to 0.155mm ~ 0.160mm (0.0061 ~ 0.0063 inches). The history of

the thick wall thickness is shown in Table 6-4.

106

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The required thickness of the thick wall depends on the neck forming

technology, the extent of diameter reduction and the formability of the aluminum
alloy. The thickness and the length of the neck wall have to be carefully designed,
looking at both the cost saving due to the reduction of the neck weight and the loss
of production efﬁciency and the quality problems due to low neck formability such
as neck wrinkles caused by the too thin thick wall.

There are three methods to reduce the neck diameter, die-necking, spin-
necking and spin-flow necking. Each forming method has advantages and
disadvantages. Spin-necking and the spin-ﬂow necking processes require the
die—necking process for pre-neck-forming. Table 6-5 shows the neck forming steps
for each type of forming to go from the 211 diameter to 206,204 and 202. There

are other combinations, but the ones shown in Table 6-5 are common examples.

108
Table 6-5 General Necking Steps for Each Reduction

 

Type of Neck Style of Neck Number of Neck Forming Step

Forming reduction
Die- 211—>209 Single Neck 1Die-necking

necking 211—>207.5 Double Neck 2 Die-necking

211—>206 Triple neck 3 Die-neckan

Quad Neck 4 Die-necking

Smooth Neck 6 Die-necking

211-2204 Smooth Neck 8~10 Die-necking

211—>202 Smooth Neck 10~12 Die-necking

Spin— 211—>206 Smooth Neck 2 Die—necking + 1 Spin-necking
necking 211—>204 Smooth Neck 2 Die necking + 2 Spin-necking
211—>202 Smooth Neck 3 Die—necking + 2 Spin-necking
Spin-ﬂow- 211—>204 Smooth Neck 3 Die-necking + 1 Spin-ﬂow-necking
necking 211—+202 Smooth Neck 4 Die-necking + 1 Spin-ﬂow-necking

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Source: The Canmaker February 1993 (6-6)
Reynolds Metals Company
L. Smith, “Barriers to Lightweighting of Aluminum D&I Beverage
Can”, SME Can Technology 1995,Singapore (6-7)

After the introduction of the 211/206 can, the appearance of the neck
became one of the most important factors which determined the necking process.
Triple neck or quad neck was considered to be less attractive than a smooth neck
in some places. Six stacks of die-necking for 211-206 neck forming resulted from
the intention to improve the bumpy neck appearance of the quad neck and triple
neck. However, smooth die-necking required too many steps to be practical. By
using the Spin-necking or Spin-flow-necking processes, the number of die-necking

steps could be decreased. The magnitude of the reduction which can be applied in

109
each die—necking station depends on the thickness of the thick wall. It is easier to

form the neck from a thicker wall.

Die-necking process

Die-necking is the conventional forming method and is the oldest in these
three methods, as shown in Figure 6-12. Die-necking tooling was used for the ﬁrst
neck reduction of aluminum two-piece cans, 211 to 209. Reducing can necks to
smaller and smaller diameters is accomplished by progressively stacking one neck
forming step onto another. The thick wall is forced into the clearance between a
necking die and a knock-out die. Plastic metal ﬂow occurs along the proﬁle of the
necking die. Processability depends on the proﬁle of the necking die, the
clearance between the necking die and the knock-out die, the can dimensions,
such as thickness, and the metal formability. Smaller reductions are easier to form.
However, the use of smaller reductions requires more steps to reduce the neck to
a Speciﬁc diameter.

Die-necking is more likely to cause wrinkles than other neck forming
methods. The important factors to eliminate the wrinkles during the die-neck
forming process are: the amount of reduction in diameter, die geometry, aluminum
alloy properties, and the thick wall dimension (thickness and variation of the

thickness). Examples of the effects of each factor are given below.

Diameter reduction: The less reduction, the better for wrinkles.

Die geometry:

Aluminum alloy properties:

Thick wall:

110
The radius of the shoulder of a necking die affects

wrinkle problem. A smaller radius tends to
prevent wrinkles, but increases the necking load.
Then the outer nose wall of the an bottom is

must be stronger.

Generally, wrinkles are more likely to occur in
stronger material. However, the stronger
materials are preferable for bottom weight
reduction. Material which has less tendency to
work harden is preferable.

A thicker wall is easier to neck down. Variation of
wall thickness tends to cause wrinkles in the

thinner areas.

111

 

 

 

 

 

KNOCKOUT

 

 

 

 

 

NECKING DIE

 

Figure 6-11 Die-necking process

1 12
Spin-necking process

The spin necking process, shown in Figure 6-13, has been used for more
than 10 years, after introducing 211/206 neck reduction. Spin-necking is done
under a lower axial load than die-necking. The can experiences an axial load of
less than 100 pounds (69). However, the small contact area between the rolling
die and the neck raises concerns about coating adhesion. Applying lubricants to
varnishes and internal coatings can reduce the problem.

The control ring controls ﬂange width variation. If all speciﬁcations are
implemented properly, ﬂange width variation should be on the order of 5 percent
(6-9).

An advantage of spin necking compared to die-necking is can height
growth. Die-necking decreases can height because of the high compressive load.
Spin necking, on the other hand, increases can height (about 0.75 mm for
reduction from 207.5 to 204) (6-12). The height increase is preferable for

lightweighting can bodies.

113

CONTROL RING

     

NECKING DISC

 

Figure 6-12 Spin-necking process

1 14
Spin-ﬂow-necking process

Spin-flow-necking, Shown in Figure 6-14, is the newest method for
necking two-piece cans. It has several advantages. A noticeable advantage is the
ability to make the reduction through a tension necking process. Spin-flow-necking
can make a 8.9 mm (0.350 inches) diameter reduction in one shot, compared to
the 1.9 ~ 2.8 mm (0.075 ~ 0.110 inches) that can be accomplished in a single step
with die-necking or Spin-necking, (6-10). Because an internal tool is used in the
spinning operation, spin-ﬂow-necking is can spin through more than one die-
necking bump.

The height of a 204 can made by spin-ﬂow-necking is 0.381 mm (0.015
inches) shorter than one made by spin-necking and 0.635 mm (0.025 inches)
shorter than one made by die necking (6-18). Spin-ﬂow-necking is the preferred
technique for lightweighting can bodies.

There are always some die-necking steps, usually 3 steps for 204 neck
and 4 steps for 202 neck from 211 can body, prior to Spin-flow-necking. Spin-
ﬂow-necking can roll out some of the defects that are result from die-necking.

On the other hand, the spin-flow-necking process is new and not fully

understood. Spin-ﬂow-necking is more complicated than other necking processes.

115

SLIDE ROLL

 

CAM RING

Wk
FORM ROLL/ 9&1

‘b — _ g“

 

 

 

 

 

 

 

 

 

 

 

 

 

ECCENTRIC ROLL

Figure 6-13 Spin-ﬂow-necking process

1 16
Neck wall weight reduction
It is difﬁcult to ﬁnd the neck wall thickness limit. Increasing the number of
steps in the necking process allows a thinner neck wall to be produced as Shown

in Table 6-6.

Table 6-6 The number of the die necking process required to
make 204, 202 neck with various thick wall thickness

 

Number of neckin process required

 

 

 

 

 

 

Initial thick wall Thickness 0.147mm 0.157mm 0.167mm
From 211 to 204 Diameter I 11 10 9
From 211 to 202 Diameter l 14 13 12

 

 

Source: G.L. Smith, ALCOA, “Barriers to lightweighting of aluminum D&I
beverage can”

It requires 14 steps of the necking process, larger space, a bigger or
longer machine, and many dies to make a 202 diameter neck on a 211 diameter
can with 0.147 mm (0.0058 inches) thick wall thickness. The usual die necking
machine has 12 -15 spindles for one necking, so 168 - 210 sets of dies are
required for 14 steps. There may be problems in can quality or production
efﬁciency when this equipment is applied to a real can line. It often happens that
the conditions which were expected before mass production was initiated have to
be changed to actually make products.

A necking method which produces no compression stress in the neck wall

would be most advantageous for reducing the thick wall thickness. Spin-flow-

117

necking is promising because it uses inner rolling dies. However, this process also
has some disadvantages. For example, earing, can height variability, and variation
of ﬂange width can occur during neck forming because of anisotropy of the
material. To control earing, three or four steps of die-necking are usually used
before Spin-ﬂow-necking. Even considering the disadvantages, spin-ﬂow-necking
is the most promising necking process for the future.

Recently, the thinnest thick wall which was could be manufactured was
0.150mm (0.0059 inches) (6-7, 6-12). Lacking any further information, this
thickness is considered to be the limit for the 202 can body with current
technology. Even if technology is developed which makes further reduction of the
thickness possible, it will probably continue to be more cost effective to reduce the
end diameter further, working toward the 200 diameter.

Neck length is another Signiﬁcant factor affecting neck weight. The die
necking process requires the thick wall to extend over the entire neck area. Neck
length can be reduced with improved technology, but a neck which is too short
spoils the appearance of the can and ease of pouring. Therefore, there is little
possibility of further reduction in the neck length.

There also is little possibility of eliminating the die necking process step
preceding Spin necking or spin-ﬂow necking because of roundness of can tops
and earing or variation of can height.

Spin-ﬂow necking doesn’t apply an axial compression load to the can body
because it uses the inner rolling die. AS a result, it causes less increase in the

neck thickness. Therefore, when spin-ﬂow necking is applied, the can body can be

118
a little Shorter before neck forming than when the die-necking or Spin-necking

processes are used. The difference in height depends on the amount of neck
diameter reduction. In one case, when spin-ﬂow technology was used, trim height
(can height before necking) for the 204/211 12-ounce can was about 0.38 mm
(0.015 inches) shorter than when the Spin-neck technology was used and 0.64mm
(0.025 inches) inches shorter than when die neck technology was used(6-11). For
a 202/211 can, when Spin-ﬂow is compared to die-necking, the difference is about
1mm (0.039 inches). Therefore, it can be concluded that use of the spin-ﬂow
technology can reduce the thick wall length by about 0.064mm (0.0025 inches) for
204/211 and about 1 mm (0.039 inches) for 202/211 can body. The can height
used in Figure 6—4 is for the 202/211 can body intended for spin-ﬂow-necking. It
can be assumed that the minimum thick wall length is 21.1mm (0.83 inches).
However, if the appearance of the an body can be changed then the neck length
can also be changed and the thick wall length will change.

Figure 6-15 Shows the neck weight which results from changes in the thick

wall thickness.

119

Neck Weight vs. Thick Wall Thickness

 

2.05 . ‘
2.00 I
1.95
1.90 +
l l ’ '

1.85 l //
/ 1

1.80 / i
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0.140 0.145 0.150 0.155 0.160 0.165 0.170

/

 

 

 

 

 

 

 

. , __ ”——

 

 

Neck Weight (g)

 

 

 

 

 

 

 

 

Thick Wall Thickness (mm)

Figure 6-15 Neck weight (Neck length is 21.1mm)

120

Can body bottom weight

The bottom of a can is designed primarily to resist the internal pressure.
The factors which determine the resistance are bottom thickness, Shape of the
bottom and the strength of the aluminum alloy used for the can body. The amount
of plastic forming at the center of the bottom is very small and it can be assumed
that the center bottom of the can body has the same thickness as the aluminum
sheet before forming. Therefore, the thickness of the bottom of can bodies can be
assumed to be the same as the thickness of the aluminum Sheet before forming.

In 1965, when the aluminum can was introduced, the thickness of the
aluminum Sheet used for can bodies was 0.495 mm (0.0195 inches). Recently it

has been reduced to around 0.285 mm (0.0112incheS) (6-5).

Bottom shape

In the US, aluminum beverage cans are designed to resist an inner
pressure of 6.3 kglcm2 (90 psi). The can bottom Should be designed to have
adequate strength to resist the pressure with minimum thickness of metal. The
stability of the can body when being conveyed in a an making line or a ﬁlling line
and the stackability when cans are stacked on one another are also important
factors to be considered. Since the end diameter has been reduced to decrease
the overall can weight, the newer bottom designs have reduced the base diameter

of the can bottom. Finite element modeling (FEM), which has been used to

121

analyze the stresses in the can body, is the most effective technique to use to
evaluate the effects of each dimension on the performance of the can bottom.
Computer soft-ware for FEM is readily available today and it has become
relatively easy to predict the stresses in cans under various loading conditions.
However, the process of the bottom forming also has to be taken into
consideration when designing the bottom because of'work hardening and other

effects. Figure 6-16 shows a typical bottom shape.

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The use of a smaller dome radius, stand radius and inner transition radius
tends to increase the ability of the bottom to resist the inner pressure. A smaller
angle between the inner transition wall and the axial direction also contributes to
the strength of the bottom. The smaller base diameter also increases the buckling
pressure of the bottom.

The lower body radius and the outer nose wall radius affect the axial load
resistance. Each dimension has limitations. A small dome radius increases the
bottom depth, resulting in lowered efﬁciency of the can volume and surface area.
A stand radius which is too small increases the likelihood of cracking in the inner
transition wall when the bottom is formed because the Sharp edge of the stand
radius on the punch prevents smooth ﬂow of the aluminum metal from the outer
stand radius to the inner transition wall. If the angle of the inner transition wall to
the axial direction is too small, inaccurate die alignment tends to create cracks. A
small base diameter reduces the resistance to axial loads and the stability of the
can, leading to problems in the can making and product ﬁlling lines.

For these reasons, the shapes of the bottom of aluminum cans made by
different can manufacturers look similar to each other even though they are all

individual designs.

Bottom thickness and metal strength

Bottom thickness and the strength of the aluminum metal used for the can
bodies are other factors which affect the inner pressure resistance. The strength

of the aluminum metal can not be easily changed because formability during wall

124

ironing and neck reduction are more important considerations. The strength of the
metal has been increased since the initial introduction of aluminum cans.
However, since switching to the 206 end diameter, it has been difﬁcult to ﬁnd ways
to apply stronger metal because of the large amount of neck forming. Aluminum
companies have continued research aimed at ﬁnding a new alloy which has a low
work hardening rate, and is easy to form into a neck, such as sample B and C
shown in Figure 6-9.

Figure 6-17 shows the relationship between bottom thickness and bottom
buckling pressure. The data are for commercial wns in USA, Europe and Asia (6-

13) including those Shown in Table 6-2.

125

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126

The resistance to the inner pressure of the bottom, called bulge strength,
has to be guaranteed to be greater than 6.3kglcm2 (90 psi). As shown in Figure 6-
16, the bucking pressure is higher than 6.3 kglcm2(90 psi). but some can bodies
have much higher pressure resistance than 6.3kglcm2(90 psi). There are two data
points which are signiﬁcantly different from the rest. The can bottoms represented

by those points were made in different way, by reforming.

Bottom reforming

The conventional bottom is formed by a body-maker, a redraw-and-ironing
press, immediately after wall ironing. It is difﬁcult to make the stand radius small
enough to increase the bulge strength of the can bottom because a small stand
radius, less than 1.0 mm (0.039 inches), leads to cracking at the inner transition
wall.

Forming the bottom in a separate operation after necking makes it
possible to decrease the stand radius of the bottom. This process is shown in

Figure 6-18.

128
Further reduction of the bottom thickness requires an extra bottom forming

process, called bottom reforming. There are two bottom reforming approaches:
forming the outer nose wall and forming the inner transition wall. In Figure 4-2,
further lightweighting of the can body in 1995 was done by this process. Bottom
reforming can also be used to decrease the base diameter.

As the diameter of the end was decreased from 206 to 204 or 202, the
need arose for bottoms with better stacking capability. For better stacking, the
bottom of one can should lock into the top of another. To achieve this goal, the
base diameter needed to be reduced. Unfortunately, smaller base diameters have
often lead to bottom wrinkling, caused when the metal is not sufficiently restrained
during the redraw operation.

The primary advantage of a smaller base diameter is increased resistance
to internal pressure, making a lighter bottom possible. Disadvantages include
decreased column strength because of deformation of the outer nose wall and
increased tendency of cans to tip over in conveying systems. Table 6-7 shows an

example of test data of the reformed bottom (6-12).

Table 6-7 Bottom performance of reformed bottom

 

I Bottom Thickness Buckling Pressure Column Strength Dgp resistance I
I 0.269 mm 6.74 gel/cm? 14053 152.4mm |

 

 

 

 

 

129
Figure 6-19 shows the bottom weight corresponding to the bottom

thickness based on data from Chapter 4. The weight of a 0.299 mm (0.0118
inches) thick bottom is 3.339 (0.00734 pounds), assuming the area of the cup
which is formed into the can bottom is constant. In reality, a deeper can bottom or

a more complicated shape can increase the area somewhat.

Bottom weight vs. Bottom thickness

 

 

 

 

 

3.4

3.3 l
3.2 ///
3.1 I

 

 

 

 

Bottom Weight (g)

3.0 .

2.9 /

2.8 r I

2.7 -
0.25 0.26 0.27 0.28 0.29 0.3

Bottom Thickness (mm)

 

 

 

 

 

 

 

Figure 6-19 Bottom weight vs. Bottom thickness

In the future, through the use of bottom reforming, aluminum beverage
can bodies with bottom thicknesses less than 0.270 mm (0.0106 inches) may be
common. In the case of 0.265 mm (0.0104 inches) thickness, the bottom weight

will be 2.959 (0.00650 pounds), a reduction of 11.4 percent.

130

Can End weight reduction

As discussed in Chapter 4, lightweighting of can ends has been
accomplished by reducing both the end thickness and the end diameter. A
decrease in the thickness of metal used has accompanied the reduction in end
diameter. It has changed from the 0.33mm (0.0130") in 209 diameter ends to
0.22mm (0.0088") in 202 diameter ends. Further reductions in can end diameter
and thickness are anticipated as the effort to lower costs continues.

Further decreases in end diameter would allow for the use of lighter gauge
metal even if the basic design of the end were unchanged. However, by modifying
the geometry of the ends, additional lightweighting can be achieved.

The buckling strength of can ends can be increased by changing their
shape. A recently developed end has a deeper proﬁle than the older ends, with a
deeper countersink, a panel wall that is more perpendicular to the horizontal plane,
and a smaller bend radius. In summary, the newer design enhances resistance to
buckling by changing the geometry of the end.

The conventional press method of manufacturing can not accommodate
the complicated geometry, so reforming of can ends has become a common
manufacturing technique. In addition to being able to manufacture the more
complicated end, reforming puts more work hardening into the end metal at some
locations such as small radii than conventional designs.

Lightweighting of the can ends is well underway in the US. All of the major
beer companies have changed end diameters from 206 to 204. Soft drink

companies are changing from 206 to 202. There was a controversy among the can

131
manufacturing and beverage industries, whether switching from 206 to 204 or 202

was the best way to reduce cost. There is still some uncertainty about both can
making and beverage ﬁlling technology. The ﬁrst change was made by a large
beer company which switched to 204. Other beer companies soon followed.
One of the concerns was settled by successfully ﬁlling more than 2000 cans per
minute. A large soft drink company switched all of their US plants to 202 ends in
1995. Other soft drink companies are joining the movement.

The further reduction of the can end diameter will be difﬁcult because of
problems with both can making and can ﬁlling, but the big problem will be the
smaller size of the aperture to pour the product which can be ﬁtted into the can
end. Signiﬁcant change in can end design will be required.

End designs which don’t use the conventional “stay-on-tab” have been
developed. The present can end design requires a large enough diameter to
accommodate the tab and the aperture. A 200 end does not have enough room for
a conventional tab. There have even been complaints about pouring difﬁculties
even with the 202 ends.

Figure 6-20 shows the trend in end thickness (6-14). From Figure 6-20,
the 200 can end can be reduced in thickness to 0.203 mm (0.0080 inches). If the
shape is the same as the present 202 end with 0.224 mm (0.0088 inches)

thickness, the weight will be around 2.12 9 (0.00467 pounds).

132

End Diameter and Thickness Trend

0.35
0.33
0.31
0.29
0.27
0.25
0.23
0.21
0.19
0.17
0.15

Thickness (mm)

 

End Diameter

Figure 6-20 End diameter and thickness trend

Source: Dr. David R. Sergent, lntemational Can Manufacturing

Technology, Chicago, September 1995.

Aluminum metal for cans

As noted in Chapter 4, the largest fraction of the total cost of an aluminum
can is the aluminum metal, 56.7 percent for the can body and 78.2 percent for the
206 can end (Table 4-1 and 4-2). Over the years, the price of aluminum has been
affected by various factors. The price decrease in the early 1990’s may have been
the result of excess supplies from Russia. Similarly, the price increase in 1995

may have been because of supply restriction by Russia. Figure 6-21 shows the

133

aluminum metal price for the past ﬁfteen years. As can be seen, there have been
large price ﬂuctuations. The difference between the highest and lowest prices was
about 0.6 dollars per pound (1.3 dollars/kg). The price in 1988 was more than
twice as high as in 1985 or in 1993.

It is not easy to reduce the weight of aluminum cans. Even a 10 percent
reduction requires extensive research and testing and heavy capital investment.
The savings achieved can easily be counteracted by metal price ﬂuctuations. A
decline in the price of aluminum will decrease the cost of aluminum cans without
any further effort. An increase in the price of the metal will raise the can cost, even
if extensive efforts are made to control the costs.

Aluminum is relatively expensive compared to other packaging materials.
Therefore, recycling of aluminum is an important business for the aluminum can
industry. Figure 6-22 shows aluminum can recycling rates and aluminum can
shipments for the last 23 years. As shown in the Figure 6-22, following the steady
increase of the aluminum an shipments, recycling of aluminum has increased.

In 1994, the rate reached 65.4 percent. This high recycling rate was the result of
the value of aluminum metal from used beverage cans (UBC) and the amount of
UBC available. The value and volume of UBC made the recycling of the aluminum
cans into a proﬁtable business. Figure 6-23 shows the price of aluminum on the
London Metal Exchange (LME) and the price for aluminum from UBC. The prices
of aluminum UBC follow the LME pn'ces.

However, it should be noted that the difference between the LME price

and the UBC price has been almost constant for four years. The average of the

134
difference was 0.124 dollars per pound. This number can be assumed to be the

cost of recycling UBC’s. The recycling cost, including proﬁt for the recyclers, is
much lower than the UBC price.

It is expected that the UBC recycling rate will increase further in the near
future. If the recycling rate increases signiﬁcantly, the overall supply of aluminum
will increase. A high recycling rate will contribute to the stability of the aluminum
prices. However, a large volume of recycled aluminum will be needed to inﬂuence

the aluminum market.

135

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Chapter 7

Discussion and conclusion

Aluminum can market

Metal cans were the second largest sector in the packaging industry in
1993. About 73 percent of total can shipments in 1994 were aluminum cans.
Aluminum can shipments are still increasing, but the rate of increase is getting
small. The competitors are PET bottles for soft drinks and non-retumable glass
bottles for beer. The use of PET bottles is increasing faster than the use of

aluminum cans.

Cost of aluminum can

The costs of aluminum can bodies and ends have been reduced, primarily
by the reduction of the metal weight. The metal cost is the highest component in
the total cost. The metal in a 12-oz aluminum can accounts for about 56 percent
for the cost of the can body, and 78 percent of the cost of the can end (206

diameter).

Reduction of aluminum weight

An aluminum can consists of two parts, a can body and a can end. The

can body can be further divided into three parts, a thick wall area, a thin wall area

138

139

and bottom area. The possible techniques to reduce each weight or thickness are
as follows.
Thick wall thickness:

The thick wall thickness must be thicker than the middle of the can wall to
get better neck formability. Therefore, the thickness depends on the neck
forming technology. There are three neck forming processes; die-necking,
spin-necking and spin-ﬂow-necking. Spin-ﬂow-necking, the newest necking
process, is the most promising process to reduce the weight of a thick wall
area.

Thin wall thickness:

The limitation to reduction of the thin wall thickness has been the column
strength of the can body. The column strength standard in the US is
90.7kg/cm2 ~ 136kglcm2 (200 lbs ~ 300 lbs), required to resist axial loading
during the seaming process on the ﬁlling line. However, new types of seamers
have recently been developed which apply lower axial loads during seaming.
It is anticipated that the column strength standard will be lowered signiﬁcantly
after the introduction of the new types of seamers, and factors other than
column strength will limit the thin wall thickness. Resistance to hoop stress
caused by internal pressure is one factor that will limit further reduction of the
thin wall.

Bottom weight:
The bottom weight is determined by thickness and shape. The bottom is

designed primarily to resist internal pressure, up to 6.3 kg/cm2 (90 psi). Well

140
designed can bottom shapes allow a light-weight can bottom. The bottom

reforming process is the most promising method to reduce the bottom weight
further.
Can end weight:

The weight of can ends has been reduced by reduction of the end
diameter and reduction of the end thickness. Reducing of the end diameter
enables reduction of the thickness of the can ends because a smaller can end
has a higher inner pressure resistance compared to a larger one with same
thickness and similar shape. Historically, the weight reduction of can ends has
been done drastiwlly by reducing the diameters. The weight of the can end
was reduced by 9.2 percent by switching from 206 to 204 and 26 percent by
switching from 206 to 202. Assuming the metal cost of a 206 can end is 78.2
percent, it can be estimated that the cost of a 204 can end will be 7.2 percent

lower and that of the 202 end will be 20.3 percent lower.

Future weight reduction

The typical 355 ml can body weighs about 11.3 g. The weight of a can
body can be reduced to around 10.1 9 using new technologies in the near future. It
would be about an 11 percent weight reduction, and about 6 percent of total cost
reduction.

There are uncertainties about future can end weight reduction. Switching to
smaller ends from the 202 end will require that some problems be solved. New

type of ends may be required for further diameter reduction, such as from 202 to

141
200. The most immediate problem limiting size reduction below the 202 diameter

is the loss of aperture area on the end. Consumers may ﬁnd that the aperture is
too small for convenience when pouring the contents into a cup or when drinking
from the can.

There are many cans with a 200 can end on the beverage market in other
countries, including Japan. Most are steel can bodies with aluminum ends, but
some are aluminum two-piece cans. The Japanese experience may not be directly
applicable to the US market. The Japanese cans, 160 to 250 ml, are smaller than
the standard 12 oz US cans (355 ml). Also, the products in the cans are coffee or
fruit cocktail drinks, not carbonated beverages.

Research is underway to develop a new can end which does not use a tab.
However, to date, there has not been. a promising development. Time will be
required to develop an effective end at the 200 size. If using a similar shape of
shell, the shell weight reduction will be 14.5 percent. The goal of the and weight
reduction at the next step will be more than 12 percent.

Therefore, the future possible total can weight reduction will be 11 ~12

percent.

Effect of aluminum metal price

It has been shown that the cost reduction of the can body and the can end
by lightweighting, can yield a total cost reduction of about 11~12 percent.
However, the percentage change in the price of aluminum metal has been greater.

The average of low prices of aluminum metal in 1982, 1985 and 1993 was around

142
0.5 dollars per pound, but the average of high prices in 1988, 1989 and in 1995

was around 0.9 dollars per pound (Figure 6-20). The price of aluminum cans
depends primarily on the price of the aluminum metal.

Stability of the aluminum metal price is a basic requirement for stability of
aluminum can prices. The price of aluminum is based on the relationship of supply
and demand. If a new use of aluminum metal for a big industry, such as the
automobile industry, develops, the price of aluminum may increase due to larger
demand.

The supply condition isn’t likely to change signiﬁcantly because aluminum
reﬁning requires a large supply of electricity and huge capital investments.

Aluminum recycling will be a very important factor to help stabilize the
price of aluminum metal in the future. The recycle rate of aluminum has been
increased since the introduction of aluminum cans. The prices of UBC (used
beverage cans) ﬂuctuate according to the LME (London Metal Exchange) prices.
As seen in Figure 6-22, the difference of the UBC prices and the LME prices is
almost constant. The average of the difference of those two prices is about 0.124
dollars per pound. Therefore, it can be assumed that the cost of recycling the
aluminum UBC is 0.124 dollars per pound including the proﬁt for recyclers. The
high recycle rate of aluminum cans will help to control the price of aluminum. Most
of the recycled aluminum comes from UBC’s. The recycle rate of the aluminum
cans in 1994 was 65.4 percent. The fraction of aluminum used for cans'in the total
aluminum market is about 15 percent (7-1). This amount is not enough to

contribute to the price reduction of aluminum metal. However, in the future, a

143

considerable amount of used aluminum from other products will start to be
recycled and if the recycle rate of aluminum UBCs increases signiﬁcantly, such as
above 80 percent, recycling should lower the price of aluminum metal.

The situation is different for other packaging materials, such as PET
bottles. Recycled PET is more expensive than virgin PET (7-2) because the
recycling cost is higher than the cost to make virgin material. A higher recycling
rate may mean an increase in price.

The aluminum recycling system will be an important factor for aluminum

cans in the future to maintain competitiveness.

Future aluminum can

Cost reduction of aluminum beverage cans to maintain competitiveness
has been discussed. Cost reduction by reducing the can weight will continue
gradually. The biggest factor of the aluminum can cost is the price of the aluminum
metal. To improve competitiveness of aluminum cans, actions other than reducing
costs will have to be taken. One is to increase the value of an aluminum can as a
beverage container, that is, by enhancing the attractiveness of aluminum cans.
The summary of present advantages and disadvantages of aluminum cans in the

beverage containers market compared to other packaging is as follows.

144

Advantage Disadvantage
Consumers viewpoints: Consumers viewpoints:
o Herrnetically sealed 0 Perception of metallic taste
0 Good shelf life 0 Not resealable
0 Light weight 0 Not see—through
0 Quick chill
' 0 Good recyclability
Beverage marketers view points: Beverage marketers view points:
0 Long shelf life 0 Limited shape option
0 Good tamper resistant 0 Limited size option
0 Light weight 0 Limited graphic option
0 Stackable 0 Not resealable

Some of the disadvantages shown above will have to be reduced to
maintain or increase the competitiveness of aluminum cans. Among the items
which an improve the attractiveness of aluminum cans signiﬁcantly are
“resealability’, “shape option” and “graphic option”. PET bottles for soft drinks are
resealable, an attractive feature. If a resealable aluminum an is developed, a
bigger market will be available. Shape options will also increase the variety and
attractiveness of aluminum cans. Simple and plain shapes of aluminum cans are
apparently less attractive in terms of appearances compared to glass or PET
bottles. The graphic options available for the aluminum can is better than for glass
or PET bottles. But when compared to other packaging, such as ﬂexible ﬁlm or
paper boxes, graphics on aluminum cans are less attractive. Improving the graphic

options for aluminum cans deﬁnitely increases their attractiveness.

 

145

The three approaches discussed above will increase the attractiveness
and competitiveness of aluminum cans. However, those improvements may also
increase the cost of the cans. Simply reducing the cost of aluminum can is not
adequate to maintain or increase competitiveness. Some method to increase the
value of the cans will be essential to maintain or increase the competitiveness of

aluminum cans in the future.

References

Chapter 1

(1-1)

(1-2)

(1-3)

(1-4)

(1-5)

(1-6)

(1-7)

(1-8)

(1-9)

(1-10)

(1-11)

(1-12)

“ Birth of the Beer Can”, Beer Can Collagors Ngﬁ Ragga, PP. 3,
January 1985.

Beth Mende Conny, “Enter the Can”, A Catalyst Ear Changa, PP. 9, 1990.

“ Birth of the Beer Can”, Bgr Can Collegqga Nam Remrt, pp.4, January
1985.

J. G. Woodroof and G. F. Phillips, Beveragea: Qamnatﬁ aria
amalgam. Chapter 7-

E. G. Maeder, The History of the D&l Can from My Perspective, pp. 1~5,
1995.

Beth Mende Conny, “An American Original”, A Catalyg far Changa,
pp.10~15, 1990.

E. G. Maeder, The History of the D&I Can from My Perspective, pp. 6,
1995.

Beth Mende Conny, “Bumblebees and Beer”, A Qatalyat far Change. PD.
33, 1990.

E. G. Maeder, The History of the D&I Can from My Perspective, pp.
8,1995.

Beth Mende Conny, “The Smiling Sherman Tank”, A Cata alyst far Changa,
pp. 40~42, 1990.

E. G. Maeder, The History of the D&I Can from My Perspective, pp.
12,1995.

Beth Mende Conny, “Maidenhead Row", A_C_ajaly_st_faL9_h_anga, pp.
51~53, 1990.

(1-13) Th Food nd Bev nt in rM rke, Business Trend Analysts Inc.

(1-14)

1994.

William LeMaire, “The 90’s in Search of an Identity”, Packaging
Strategies ’94 conference, 1994.

146

147

(1-15) MPC Chronicle, “Can shipments in 1995”, PP. 4, March 1996.

(1-16) “The food and beverage container market”, A business information report
from: Business trend analysts Inc, 1995.

Chapter 2

(2-1) G.L. Smith, ”Barriers to Lightweighting of Aluminum D&I Beverage Can”,
SME Can Technology 1995,Singapore.

(2-2) Scott C. Biondich, Aluminum Company of America, “Alcoa B64 reformed
shell forming process”, September 1989.

(2-3) Harry W. Lee, C. Thomas Payne, “Technical update on spin ﬂow necking”,
Technology update for canmaking at lEF P, 1993.

(2-4) Wliliam Jowitt, Camaud Metal Box, “Base proﬁle reforming process”,
Presented at lEFP 1993.

(2-5) Vlﬁlliam Jowitt, Camaud Metal box, “Development in 2-piece can body
forming” Presented at Can Technology 1995, Singapole.

(2-6) The Canner ”The end for aluminum?”, PP. 29~32, June 1995.

(2-7) Th nm k r, "Survey hits a raw nerve, PP. 19~20, June 1995.

(2-8) Qantgh lntamatignal, “In bev cans, It ain’t over yet”, PP. 12~18,
June/July 1995.

Chapter 3

(3-1) Aluminum Company of America, Presentation about their company, 1994.

(3—2) Aluminum Company of America, Presentation about their material, 1994.

(33) “Aluminum Easy Open End Manual”, Aluminum Company of America.

Chapter 4

(4-1) 1he_C_an_ne1 “Steel takes center stage”, PP.28~32, July 1995.

(4-2)

(4-3)

(4-4)

(4-5)

148

Reynolds metals Company. Richmond Vlrginia, 1995.

The Canmaker, “No let up aluminum lightweighting”, PP. 44, September
1 995.

G.L. Smith, “Preformed Cup for Small-Based Beverage Cans”
lntemational Can Manufacturing Technology in Chicago, September
1994.

The Canmakar, “Aluminum Lightweighting”, pp. 44 1995.

Chapter 5

(5-1)

(5-2)

(5-3)

(5-4)

(5-5)

(5-5)

(5-7)

(5-8)

(5-9)

(5-10)

(5-11)

The Canmakar, “US can shipments by sector”, Can Manufacture Institute,
PP.18, May 1995.

The Canner, “Steel takes center stage”, PP.28~32, July 1995.

Amarign Metal Market “UBC recycling reach 65 percent”, PP.7, March
24, 1995.

Packaging Technglagy é Enginaaring “Design Strategies Help Packagers
Overcome Environmental Hurdles”, PP.22~23, March 1995.

W, “A Snapshot of Waste Generation and Recovery”,
pp. 50~52, January 1995.

W, “A knockout year for aluminum can recycling”,
PP27~34, May 1995.

Reynolds Metal Company, “U.B.C. Distribution System Industry Structure”
October 1995.

Daivid R. Willbum and Lorie A. Wagner, “ Aluminum Recycling Industry”,
Aluminum Availability and Supply, A Minarala Availability Aapgaigl, pp.
93, 1993.

P in i , “The Legal Impact”, PP.20~22, June 1993.

Businags ere, “Aluminum can recycling reach 65 percent”, March 21,
1995.

Bevemga Wang “At What price?”, PP. 46~50, June 1995.

(5-12)

(5-13)

(5-14)

(5-15)

(5-16)

149
Tha Cannar “The end for aluminum?”, PP. 29~32, June 1995.

Pagkaging Tachnglggy & Engingring “Design strategies help packagers
overcome environmental hurdles”, PP. 22, March 1995.

Resource Recygling, “A snap shot of waste generation and recovery”, PP.
52, January 1995.

Packaging Digest, “The Legal Impact”, PP.20~22, June 1993.

Rmama Regucling, “A knockout year for aluminum can recycling”, PP28,
May 1995.

Chapter 6

(6-1)

(5-2)
(5-3)

(5-4)
(6-5)

(5-6)

(6-7)
(6-8)
(5-9)

(6-10)

(6-11)

G.L. Smith, “Barriers to Lightweighting of Aluminum D&I Beverage Can”,
SME Can Technology 1995,Singapore

Data from Mitsubishi Materials Corporation, Aluminum Division, Japan.
Tha Canner, “Strong yet sensitive”, PP. 28, February 1996.

Selwyn M. Knap, “Can design transformation”, ﬂaminum alloys tor
Packaging ll, PP.99, 1996).

G.L. Smith, “Barriers to Lightweighting of Aluminum D&I Beverage Can”,
SME Can Technology 1995,Singapore

Tha Canmaker, “ 202 Necking”, PP. 49, February 1993.

G.L. Smith, “Barriers to Lightweighting of Aluminum D&I Beverage Can”,
SME Can Technology 1995,Singapore.

Dean Jonson, “Necking Two-Piece Beverage Cans in the 90’s”, Aluminum
Allgya pr Pagkaging ll, PP. 164, 1996.

Dean Jonson, “Necking Two-Piece Beverage Cans in the 90’s”, ﬂaminum
Allgya mr Packaging ll, PP. 165, 1996.

Tha Qanmakar “Rising Tension” , PP. 36, January 1993.

Harry W. Lee, C. Thomas Payne, “Spin-Flow Necking”, lntemational Can
Manufacturing Technology. SME, 1992.

(6-12)

(6-13)

(6-14)

(6-15)
(6-16)

(6-17)

(6-18)

(6—18)

150

William Jowitt, “Development in 2-piece Can Body Forming”, Can
Technology 1995, Singapore.

Kiyofumi Ito, Shin Tsuchida, “Trend of Aluminum Beverage Can”,
Sumitomo i h M l T nol i I R s, 1993.

Dr. David R. Sergent, “Material Considerations, Beer and Beverage”,
lntemational Can Manufacturing Technology, Chicago, September 1995.
Tha Canner, “The end for aluminum ?”, PP. 29 June 1995.

Reynolds Metals Company, Richmond Virginia, 1995.

Wag, “Aknockout year for aluminum can recycling “, PP.
28, June 1995.

Reynolds Metals Company, Richmond Virginia, 1995.

Harry W. Lee, C. Thomas Payne, “Technical update on spin ﬂow
necking”, Technology update for canmaking at IEF P, 1993.

Chapter 7

(7-1)

(7-2)

Rovert G. Adamson, “System Innovations Take Aseptic Cartons into New
Market and New Product Categories”, Bev-Pak Americas, 1996.

Waata Age, “PET : No. 1 is” PP. 48~61, September 1994.

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