Modeling of thrust and torque for drilling PTFE materials

Polytetrafluoroethylene (PTFE) as a material is widely used for ultra-clean flow control elements to replace metal in photolithography machines. However, delamination occurs during drilling and its creep resistance is poor. The traditional metal drilling model is not suitable for the PTFE. Hence, in this study, a mechanistic model to predict the thrust and torque distributing along the cutting edges is established. Firstly, the mathematical expression of the drill geometry is reviewed. Then, the rectangular cutting is converted to the oblique cutting utilizing coordinate transformation, this connects drilling and oblique cutting. Secondly, the forces on the rake and relief faces are taken into account and separated into multiple cutting loads. The discretized cutting loads are combined to develop a mechanical model for predicting the thrust and torque. Finally, the drilling experiments are conducted to verify and improve the model. The results show that the maximum errors of thrust and torque are 12% and 20%, respectively, the average errors are 5% and 9%, respectively. The proposed model could be used to guide the manufacturing of the key components in the semiconductor equipment industries.