Study on surface morphology of titanium alloy curved thin-walled parts by longitudinal-torsional composite ultrasonic assisted milling

In order to obtain titanium alloy curved thin-walled parts with better surface quality, longitudinal-torsional composite ultrasonic assisted milling (LTCUAM) was studied. The tool tip trajectory model and the surface roughness model of LTCUAM were established. It was found that LTCUAM could obtain lower surface roughness than common milling (CM) through analyzing the theoretical model. Finally, the effects of milling parameters and acoustic parameters on surface morphology were studied by orthogonal test and single factor test. The experimental results indicated that the surface roughness Ra and the surface arithmetic average height Sa value decreased in different degrees after LTCUAM. However, various milling parameters and acoustic parameters had different effects on the reduction of Sa and Ra. With the increase of ultrasonic amplitude, both Sa and Ra displayed a trend of decreasing first and then increasing. With the increase of spindle speed, both Sa and Ra decreased first, then increased and then decreased. With the increase of the feed per tooth, both Sa and Ra basically showed an increasing trend. The results demonstrated that better surface texture and surface quality can be obtained with lower feed per tooth, medium ultrasonic amplitude and spindle speed.