Abstract
A mechanistic model to predict thrust force and torque in drilling is presented and its application to bone drilling is evaluated. The cutting action at the drill point is divided into three regions – the cutting lips, the outer portion of chisel edge (the secondary cutting edges) and the inner portion of chisel edge (indentation zone). Models that account for the unique mechanics of the cutting process for each of the three regions are formulated. The models are calibrated to the workpiece using specific cutting pressure equations with modification to take advantage of the characteristics of drill point geometry. The models are applied to predict thrust force and torque for drilling bovine cortical bon and evaluated for a wide range of spindle speed and feed rate. Prediction results for cutting lips, chisel edge and entire drill point agree well with experimental data. Only torque predictions for the chisel edge are lower than experimental results at some drilling conditions.
