Vertical machining center accuracy characterization using laser interferometer - Part 1. Linear positional errors

This paper presents the results of accuracy characterization of a Vertical Machining Center (VMC) in the form of linear errors and temperature variati on using a low powered He-Ne laser (Renishaw(R)) calibration system along w ith environmental controller unit. The machine investigated is Cincinnati M ilacron Sabre 750 three axes CNC VMC with Acramatic 2100 CNC open architect ure controller. Temperature distribution of the machine was measured using three temperature sensors strategically attached to predetermined locations on each axis guides. 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 temperatur e, air pressure and relative humidity). Results show that axis drive motors are the major heat sources. Linear positional accuracy is best when the ma chine is in cold condition and deteriorates with increasing machine operati on time for all three axes. X-axis had worst linear displacement accuracy a nd maximum reversal errors among the three axes being tested. (C) 2000 Else vier Science B.V. All rights reserved.