DEVELOPMENT OF A DRILLING PROCESS WITH TORQUE STABILIZATION

Variation in cutting torque often occurs while drilling a deep hole or a workpiece of composite stiffness. Torque variation is closely relat ed to the rise in frictional torque between the swarf and the workpiec e as a hole becomes deeper, and to the change in material property in a laminated composite workpiece. Torque variation degrades the efficie ncy and stability of the drilling process. This study seeks to elimina te large torque variation during drilling by making the cutting torque constant through an active control method. Approximate dynamic modeli ng of the drilling torque is proposed, and an adaptive PI control algo rithm is applied to regulate torque variation. Numerical simulations a nd experiments on torque-controlled drilling processes are carried out . Results show that torque stabilization and machining time reduction can be achieved by active control. Experimental results validate the d ynamic model and control algorithm.