Single Axis Error Compensation of Ultra Precision Lathe Using Dual Servo Actuation

Abstract

Steady increase in the precision requirement of today’s manufacturing industries is the driving force for the development of new and innovative precision machines. The accuracy of the machined workpiece depends widely upon the accuracy of the machine tool and its individual component and sub-assemblies. In the current work, we have put forward a dual servo error compensation mechanism for an ultra-precision lathe to compensate the tool positioning error along Z-axis due to the Z-axis following error caused by the machine’s servo and X-axis form error along the Z direction. A monolithic single axis piezo-actuated flexure based mechanism is designed to compensate the micro-metric positioning error of the lathe to provide nanometric level machine accuracy. Experiments have been conducted to verify the machine’s performance characteristics with and without the fine tool servo (FTS) compensation using a high resolution capacitance sensor. The surface roughness of 9nm has been achieved using the following error compensation mechanism alone with a primary profile height Pt of 1.285μm. The results were evident that the surface roughness has been improved tremendously with the Z-axis following error compensation mechanism. Further experiments have been carried out in order to improve the primary profile of the machined surface by studying the errors along the Z axis and formulate controller logic in order to compensate the cumulative error along the Z axis in real-time. The surface roughness of 4nm and profile height of 0.3μm has been achieved using the compensation system. Further studies are also being carried out in order to study the form error of the machine and actively compensate all the errors along Z axis cumulatively in real-time