Development of PCBN micro ball-end mill with multi-edge and spherical flank face

Micro mills play an important role in micro-milling applications for precision micro-parts such as optical molds, microsensors, etc. With the wide application of difficult-to-machine materials in such micro-parts, poor machining quality and rapid tool wear have become serious problems restricting the application of micro-milling technology. In order to achieve higher machining quality and longer tool life, a PCBN micro ball-end mill structure with multi-edge and spherical flank face (MSPBM) is designed. This structure enables multiple edges to participate in cutting at the same time, which can share the cutting force to reduce tool wear. In addition, the structure of the spherical flank surface makes the flank surface fully in contact with the machined surface, which enables CBN particles to micro-grind the machined surface to achieve the effect of milling-grinding combined machining, and the better surface quality can be obtained. The grinding experiments are carried out to optimize fabrication process parameters based on grey relational grade theory and the MSPBM with 0.2 mm diameter is fabricated through multi-axis linkage grinding and micro-compensation of motion axes. Then, slot milling experiments are carried out on the martensite stainless steel to investigate the micro-milling performance of the mill, and the surface topography, surface roughness, and the tool wear topography are observed and analyzed. The results show that the surface quality and wear resistance of the MSPBM are improved compared to the standard ball-end mill. The structural design principle of the micro mill can be used to guide the design of mills for high-quality machining of difficult-to-machine materials.