Autonomous Compensation of Thermal Deformation of Machine Tool

Abstract

The requirements for higher dimensional and geometrical accuracy of machined products are increasing recently in many fields of precision machining. There are many factors which influence the machining accuracy. Above all, the machining error due to the thermal deformation of machine tool is recognized as one of the most serious problems to be solved in order to assure high quality of products. The thermal deformation of machine tool is influenced by many factors such as the structure of machine tool, the thermal conditions in the environment, the cutting conditions and so on. In general it is not possible to detect the thermal deformation directly at the tool center point (TCP) between moving tool and workpiece because of the existence of chips and cooling lubricant. In addition it is difficult to compensate the thermal deformation which is unsteady and not repeatable by the use of a conventional CNC controller which is designed to generate the feed commands exactly according to the given program. An open-architecture CNC controller provides one solution to solve this problem, since it can accommodate the real time compensation of the cutter path (Altintas 1992; Mitsuishi et al. 1997; Yamazaki et al. 1997). The user can implement his own control and compensation rules in order to improve the performance of machine tool.