UBC Theses and Dissertations
Precision turning of shafts with piezoelectric actuator tool Jun, Martin Byung-Guk
There is an increasing demand for high tolerances and good surface finish for most industrial applications of shafts such as the seats of roller bearings or gearwheel compression joints. A grinding or ultra-precision machine tool is used to finish these parts in the final production sequence because the conventional turning machine cannot meet the tolerances. This thesis investigates the use of a piezoelectric fast tool servo designed for precision turning of shafts on a conventional turning machine. In doing so, the grinding operation, the final process of precision machining, can be eliminated, which leads to significant savings in time and cost. A piezoelectric fast tool servo previously designed and developed for chatter vibration suppression is used for the investigation. It is mounted on a turret of a standard CNC turning center and is modeled as a second order dynamic system. Sliding mode control or variable structure control is used to control the actuator, taking advantage of its characteristics of robustness against disturbances and parameter uncertainties. The concept of using the piezoelectric actuator to accurately position the tool on a conventional machine and the effectiveness of the control scheme are verified both in simulations and experiments. Cutting experiments are carried out to identify the cutting conditions which produce the required surface quality. The effect of feedrate, cutting speed, tool geometry, and use of cutting fluids are investigated The results show that the surface quality that grinding offers can also be attained with the help of the piezoelectric actuator and proper selection of the cutting parameters.
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