Investigation into micromilling processes for micro thin walls made of Ti-6Al-4V material by customized polycrystalline diamond end mill

Abstract. Titanium alloy, as a material with high specific strength, is prone to severe tool wear during machining, leading to deterioration in the surface quality of the workpiece and presenting significant machining challenges. Therefore, to improve the machining quality of titanium alloy thin walls, the PCD (polycrystalline diamond) micro-end mill with straight peripheral and end cutting edges has been designed and fabricated for this specific task, and the key process factors relating to micromilling of Ti-6Al-4V thin walls have been studied in this paper. A method of identification of specific cutting force is proposed for a customized PCD micro-end mill using a mechanistic force model. Micromilling experiments have been carried out considering different cutting-edge rake angles and cutting fluids to identify the specific cutting force through a linear regression method. The surface roughness, tool wear, and thin-wall dimensional error have been also evaluated. Experimental results show that the specific cutting force has an approximately linear correlation with the cutting-edge rake angles. But the surface roughness, tool wear, and dimensional error have obvious nonlinear relations with the rake angles. Oil mist is the better processing fluid compared with dry cutting and jet cold air, which produces not only the smallest specific cutting force but also the smallest surface roughness value and dimensional error. When machining titanium alloy thin walls with a −45° cutting-edge rake angle tool, the oil mist lubrication process reduces the relative dimensional error from 7.1 % (observed under a dry-cutting process) to 4.5 %. This study provides theoretical and technical guidance for the machining of titanium alloy and other difficult-to-machine material components in the aerospace industry.