Surface finishing is one of the most critical manufacturing processes as it improves the corrosion and fatigue resistance of a product. Among many available surface finishing technologies, Magnetic-Field Assisted Finishing (MAF) is a promising finishing process that uses a slurry mixture made of ferromagnetic and abrasive particles in a liquid medium, also known as a brush. The brush attached to a magnetic tool directly interacts with the surface of a workpiece and removes surface imperfections and defects to achieve a desired surface finish. The MAF process enables precise control of several parameters such as brush rotational speed, feed rate, gap distance, and the constituents of the MAF brush. These constituents encompass factors such as the size and type of abrasive and ferromagnetic particles. The control over the parameters allows for surface finishing to be precisely regulated down to the nanometer scale. This research explores various aspects with the aim of improving the quality and processing time of the MAF process. Due to the recent inception of MAF, there is still a lack of understanding regarding the application of MAF on various metallic materials, large workpiece areas, and freeform geometries. In the first part of this study, a 2k−1 fractional factorial design (FFD) was used to investigate and identify optimal processing parameters on mold steels. The optimal processing parameters could be obtained by studying the interaction among all of the processing parameters. After the FFD, additional experiments were conducted to enhance the efficiency of the polishing process starting from a rough surface. Finally, a multi-step MAF process on the HP4M mold was designed based on the results obtained from both the FFD and additional experiments. The MAF performance was compared to manual finishing, where the final roughness of 26 nm and 20 nm were achieved with MAF and manual finishing, respectively, starting from the initial surface roughness of 434 nm. Additional experiments were conducted on an AISI S7 steel workpiece using different processing parameters but employing the same analytical approach. The optimized parameter settings significantly improved the final surface roughness from 507 nm to 45 nm. Subsequently, the MAF process was employed to polish large chrome-coated sheet metal samples and the process was investigated to determine the optimal processing parameters. Based upon profilometry measurements, introducing a stiffer brush containing a greater fraction of ferromagnetic particles by weight improved the MAF performance in finishing sheet metal samples. Additionally, using the smallest black ceramic (BC) size (3 μm) resulted in a superior surface finish. The second part of the study was closely related to the previous study but focused on the finishing of large sheet-metal surfaces. First, the optimal processing parameters were determined by applying a small-scale setup to finish chrome-coated metal sheet samples. Subsequently, the identified parameters were implemented in the continuous setup that successfully finished the sheet metal samples with a larger area. This application of optimized parameters in the continuous setup enhances the effectiveness and efficiency of the overall finishing process. Finally, a systematic approach was developed to identify the optimal processing conditions regarding the abrasive particle size, iron particle size, and traversing passes. The study yielded the appropriate brush constituents to improve the efficiency of the MAF process. To enhance material removal and improve the surface quality of the workpiece, it is recommended to use smaller BC polishing media and larger iron particle sizes. The optimal number of passes varied depending on the size of the BC. As the BC size decreased, optimal conditions required fewer passes, resulting in a better surface finish. Simulations were conducted to explore the effects of the iron particle size on the brush constituents. The investigations demonstrated that the larger iron particles are subject to a more powerful magnetic force. As a result, they form robust chain-like structures that exhibit a two-body abrasion mechanism, providing enhanced processing capability. Conversely, the smaller iron particles experience comparatively weaker magnetic forces between them, enabling them to roll freely, resulting in a three-body abrasion mechanism. The current status of the MAF process is still not mature enough to be implemented in practical industrial applications, but his work determined the optimal contents of the brush constituents which will contribute to making the MAF process more practical.
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