Analytical model of exit burr height and experimental investigation on ultrasonic-assisted high-speed drilling micro-holes

Abstract

Micro-holes drilling of titanium alloy using ultrasonic-assisted high-speed drilling (UAHD) has been proven to be effective in improving the height of the exit burr. The height of the exit burr is considered as one of the key output variables to evaluate the machining quality of micro-holes. Investigating the height of the exit burr and its modeling development provides great help to understand the effects of processing parameters on the burr height. This investigation will present an analytical model for the height of micro-holes exit burr. The acoustic softening effect is considered in this model. The approaches of the modeling development start from the work done by each part, including the axial force work, material deformation work, and total work. Then the burr height is calculated according to the conservation of energy. To verify the model, a single factor experiment of titanium alloy micro-holes was designed. The trends of analytical burr heights were consistent well with those of experimental results. Both the analytical model and the experimental results showed that the height of the exit burr was negatively correlated with the ultrasonic amplitude and spindle speed, and positively correlated with the feed speed. Also, the micro-holes exit morphology was observed under different processing parameters. The results showed that larger amplitude, spindle speed, and smaller feed speed were beneficial to the micro-holes exit with higher shape accuracy.