An overhung boring bar servo system for on-line correction of machining errors

In this paper, a newly designed overhung boring bar servo system equipped with an on-line compensation function for machining errors is presented. The overhung boring bar that has been developed is made with a pair of concentric bars with an outer diameter of 14 mm and an overhung ratio of 8:1. A piezoelectric (PZT) actuator was incorporated in the boring bar servo system to achieve on-line compensation. A control technique, “forecasting compensatory control” (FCC) was implemented in the boring bar servo system to perform an on-line prediction of the machining errors encountered. An off-line simulation was performed to test the adequacy of the parameters being used in the FCC models adopted. Results of the cutting tests with the boring bar servo system show that to the extent limited by the instrument capability, a boring bar servo system using an FCC methodology can be a very cost-effective tool for on-line compensation of machining errors in the precision boring of holes with high aspect ratios.