Formation mechanism and controlling technique for fabrication of extremely sharp diamond micro mills

Abstract

The extreme sharpness for superhard micro mills is urgently needed to improve the surface quality, restrain size effect and suppress burr formation for the widely used miniature components. Therefore, laser cutting and precision grinding are coupled to form a hybrid method for the fabrication of diamond micro mills with extremely sharp edge. Firstly, the laser cutting simulation of polycrystalline diamond (PCD) based on various laser energy density and laser scanning speed was conducted to provide temperature distribution. Then the laser cutting experiments were conducted, and the influence of laser cutting parameters applied on the machining consequences (kerf width, cutting cycles, affected layer thickness, and surface roughness of cutting section) were analysed according to the simulation model. On this basis, the laser energy density and scanning speed were optimized as 175 J/cm2 and 0.2 mm/s respectively to obtain the smooth and uniformly graphitized surface. Moreover, the grinding experiments were conducted on the cutting section obtained by the optimized laser parameters, the impact of the abrasive grain size, grinding depth per path and feeding speed on the grinding results were studied, these grinding parameters were optimized as 1 μm, 1 μm, and 2 mm/min to realise the micro abrasion during grinding process. In this way, PCD micro end mills (PCDMs) with surface roughness Sa of 57.3 nm, effective length of 600 μm, diameter of 400 μm, and radius of cutting edge of 0.19 μm were fabricated. Finally, the micro-milling experiments with PCDMs were performed on the Ti-6Al-4V material, the micro slots and thin-walled structure were processed with almost no burrs being observed and the obtained surface roughness Sa of 18.3 nm. With the obtained machining results, the remarkable cutting performance of PCDM was validated.