Simulation study on effect of cutting parameters and cooling mode on bone-drilling temperature field of superhard drill

To overcome strong drilling force and significantly high temperature during orthopedic surgery, two medical drills with different geometrical shapes were designed by using superhard materials. The bone-drilling temperature fields under different cutting parameters and cooling modes were simulated by using a brazed step drill and a brazed twist drill. Results showed that given a fixed feed speed, the maximum bone-drilling temperature using the brazed step drill under 500 rpm was 33.5 A degrees C, which increased to 58 A degrees C under 2000 rpm. Meanwhile, the maximum bone-drilling temperature using the brazed twist drill under 500 rpm was 42.9 A degrees C, which increased to 70.1 A degrees C under 2000 rpm. Given a fixed drill speed, the maximum bone-drilling temperatures of both drills varied as feed speed first increased and then decreased. When the feed speed increased from 0.5 to 1.7 mm/s, the maximum bone-drilling temperature of the brazed step drill was proportional to the feed speed. With the further increase in the feed speed from 1.7 to 2.0 mm/s, the maximum bone-drilling temperature decreased. The bone-drilling temperature of the brazed twist drill varied similarly, except for reaching the peak at 1.4 mm/s. The bone-drilling temperature of the brazed step drill was always lower than that of the brazed twist drill under all cutting parameters. The normal saline spray cooling had the best cooling effect, followed by the normal saline pouring cooling and air cooling. The maximum temperatures of these three cooling modes were 43.8, 52.6, and 70.1 A degrees C using the brazed step drill.