Machine tool 3D volumetric positioning error measurement under various thermal conditions

Abstract

To manufacture good quality or accurate parts, the measurement and compensation of three dimensional volumetric positioning errors of a machine tool are very important. Using a conventional laser interferometer to measure the straightness and squareness errors is very difficult and time consuming. Recently, Optodyne has developed a laser vector technique for the measurement of 3D volumetric positioning errors, including 3 linear displacement errors, 6 straightness errors and 3 squareness errors in a very short time. Using this laser vector technique combine with the data obtained from a set of thermocouples placed at key locations of the machine tool structure, the relations between the machine temperature distribution and the 3D positioning errors can be measured and modeled. The results can be used to compensate the 3D volumetric positioning errors under various thermal conditions. Reported here are the definition of the 3D volumetric positioning errors; the basic theory and description of the laser vector technique; the temperature sensors and the laser vector technique measurement results obtained on a vertical CNC machining center under different spindle load, machine temperature and environmental temperature.