Investigation of kinematics error influence on on-machine measurement for ultra-precision turning

Shift from offline measurement to on-machine measurement (OMM) is urgently needed for closed-loop control for ultra-precision machining processes. OMM can avoid the errors caused by repositioning workpieces and increases the inspection efficiency. In this work, an in-house designed interferometer probe was integrated on a 3-axis ultra-precision diamond turning machine for OMM. However, as the probe is carried on the motion slides, kinematics errors of the machine tool will inevitably affect the OMM results. To investigate the influence of kinematics errors, simulation analysis was performed and the four primary error components in the sensitive measurement direction were measured by capacitance sensors using the reversal method. Finally, an OMM experiment of an optical flat surface was carried out. The results prove that OMM error was dominated by the C axis tilt error E_BC with a 2 UPR (undulations per revolution) component along circumferential direction.