Effect of tool center point angles on drilling performance in robotic cortical bone procedures

This study investigates the effects of different tool center point (TCP) angles on drilling precision and accuracy in cortical bone using a six-axis robot. Tool paths were generated using simulation software, and various TCP angles and corresponding robot postures were implemented in a real-world setting. To assess dynamic characteristics, experimental modal analysis was performed to measure natural frequencies and damping ratios (DRs) across the different configurations. Based on these results, spindle displacement was measured to quantify vibrations during drilling, allowing identification of configurations associated with lower vibration levels. To validate these findings, drilling experiments were conducted on cortical bone specimens to compare cutting performance. The results showed a 20.77 % average reduction in drilling torque and a 7.42 % decrease in the delamination factor (DF), which affects the bonding strength between the cortical screw and the bone. These findings suggest that the selection of TCP angle parameters may influence drilling performance and hole quality, underlining the relevance of robotic-assisted drilling (RAD) angle control in cortical bone surgery.