Study on machinability of three-step drill in drilling Ti6Al4V

Abstract

As the research progresses, titanium alloy materials have more applications in aerospace and other fields. However, problems such as chip winding and serious tool wear are easy to occur in the machining process. In this research, the three-step drill has changed the main cutting-edge structure, which is more conducive to chip breakage. Firstly, the drilling force of the three-step drill bit is analyzed, and the alternating stress that makes the chip thickness change is obtained by the cutting-edge structure of the three-step drill bit. The simulation and experiment are verified by each other, and the feasibility of three-step drilling to improve the processing quality is obtained. The results show that the improved drill has good chip breaking performance, low thrust force, and better machining performance compared with the twist drill. In addition, the improved drill can obtain a more complete inner wall of the hole and reasonably improve the surface quality. Through experiments, it is found that changing cutting parameters such as feed rate has different effects on chip thickness, thrust and tool wear. It was found that the drilling force was reduced by drilling Ti6Al4V material with the three-step drill. Moreover, the three-step drill can produce smaller chip thicknesses and make the chip more prone to breakage when compared with the twist drill. The high wear of three-step drill bits can also be better weakened by coating materials.