Experimental Study of Helical Milling of High Volume Fraction SiCp/Al Composites
The work aims to analyze the material removal mechanism, simulation and experimental results of SiCp/Al composites with a volume fraction of 55％ under the conditions of helical milling machining, to summarize the rules affecting the accuracy of the hole diameter and the surface quality, to meet the technical requirements of the hole diameter H7 and reduce the surface roughness, and at the same time, to provide a certain theoretical basis for the helical milling machining of SiCp/Al composites with high volume fractions.Firstly, the force condition of single silicon carbide particles in SiCp/Al composites and three different removal forms of particle removal were analyzed based on the rule of motion of helical milling. Secondly, the aluminum matrix, silicon carbide particles and the tool were modeled separately to ensure that the particles were randomly and uniformly distributed inside the Al matrix, to simulate the removal of silicon carbide particles in the machining process, and to analyze the effects of the three typical removal forms on the surface roughness. Then, a helical milling experimental study was carried out on SiCp/Al composites with a volume fraction of 55％ using a VDF850A vertical machining center, and holes with a diameter of 6 mm were made in 8 mm-thick SiCp/Al composites using a 4 mm-diameter PCD milling cutter. An inner diameter micrometer, a SJ-210 handheld roughness tester, a VHX-500F super depth of field microscope and SEM3100 electron microscope equipment were used to measure and observe the experimental results. Through the response surface method, spindle speed, feed rate and pitch were selected as optimization variables, and hole diameter and surface roughness as optimization indexes. A response analysis model was established to obtain the multiple regression equations of cutting parameters and optimization indexes, and to study the interaction between each process parameter. Finally, the better process parameters obtained from the response surface method were experimentally validated.For the SiCp/Al composite material, compared with drilling, the hole making helical milling had better advantages, reflected in the smaller exit edge defects, which could reduce the size of the drill cap chip to a greater extent. When the spindle speed is 3388 r/min (the cutting speed is 42.575 m/min), the feed speed is 175 mm/min, the pitch is 0.26 mm, the hole size is 6.018 mm, and the surface roughness Ra is 1.5303 μm, which is a combination of the parameters to satisfy the technical requirements of the hole diameter H7 and the surface roughness of the process.The most significant effect on the surface roughness of SiCp/Al composites with high volume fraction after machining is the pits created when the SiC particles are pulled out, when the peak of the surface roughness is close to the radius of the SiC particles. Compared with particles being extruded and particles being pulled out, particles being cut off can get better surface quality, and appropriately increasing the cutting speed can increase the probability of particles being cut off.
SiCp/Al compositeshelical millingcutting mechanismfinite element simulationsurface quality
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