Investigation of the Thrust and Torque Generated during Drilling Processes

Abstract

This thesis presents a study of the thrust and torque generated during drilling processes, with emphasis on applications to perform on-line monitoring of drilling processes. Two mathematical models are developed for quantitatively relating the thrust and torque to the machining parameters and drill geometry. A modal testing is conducted to identify the effect of drill structure on thrust and torque generation. In addition, a prototype sensing system is employed to measure the thrust and torque in an on-line fashion. The prototype sensing system shows great promise for integration with the mathematical model to produce untended drilling systems.<P>Analytically, an unique approach for evaluating the thrust and torque generated during drilling processes is developed. Mathematical models relating drill geometry (point angle, helix angle, drill radius and web thickness) and cutting parameters (feed rate and spindle speed) are established based on machining science. Specifically, a force analysis is performed on the geometry of twist drill. Experimentally, a dynamometer for measuring the thrust and torque during drilling is designed and fabricated. The sensing system is calibrated and tested to demonstrate the capability of detecting the dynamic variation of the generated thrust and torque. Effects of the cutting parameters are investigated and explained through a two-level design experimentation.<P>The sensing system described in this thesis is a prototype of a sensorbased drilling system. A strategy for implementing such a system on the shop floor is proposed, suggesting the direction of future research for achieving high quality and productivity with the drilling process.