Vertical machining center accuracy characterization using laser interferometer

This paper presents the results of accuracy characterization of a Vertical Machining Center (VMC) in the form of linear / angular errors and temperature variation using a low powered He-Ne laser (Renishaw (R)) calibration system along with environmental controller unit. The machine investigated is Cincinnati Milacron Sabre 750 3-axes CNC Vertical Machining Center with Acramatic 2100 CNC open architecture controller. The accuracy of the VMC is characterized in the form of geometric and thermal errors as a function of machine tool nominal axis position, temperature distribution and environmental effect (air temperature, air pressure and relative humidity). The measured temperatures in conjunction with the geometric models are used to predict machine tool geometric and thermal errors. Results show that axis drive motors are the major heat sources. Linear positional accuracy is best when the machine is in cold condition and deteriorates with increasing machine operation time for all 3-axes. X-axis had worst linear displacement accuracy and maximum reversal error among the three axes being tested. X-axis pitch and Y-axis yaw error were highest angular errors of the VMC.