Torque control for a form tool drilling operation

Torque control through feed manipulation can provide significant machining economic benefit for drilling processes by preventing tool breakage and red ucing cycle time. This paper presents the dynamic modeling and real-time to rque control for a form tool drilling process. The form tool produces a des ired shape in a workpiece through a drilling process. In this study, the fo rm tool drilling process resembles the combination of drilling, reaming, co unter-boring, and chamfering operations. The machining process is modeled a s a linear system with variable gain due to the form tool geometry. The pro cess is also subject to unknown disturbances such as unpredictable chip jam ming and tool-workpiece friction. Spindle motor power and speed measurement s were used to estimate drilling torque for cost effective practical implem entation. an input-output pole placement controller with previewed gain sch eduling was designed and implemented. Through experimental studies, this co ntroller was shown to effectively regulate tool torque and hence avoid tool breakage, by manipulating the feed during drilling, and reduce cycle time compared to current practice.