Real-time compensatory control of thermal errors for high-speed machine tools

This paper proposes a developmental procedure of a real-time thermal error compensator for a high-speed machine tool (HSMT). A vertical-type HSMT having a slant column with lightweight moving slides is used to investigate thermal characteristics. Since spindle speed is very fast in the HSMT, a large amount of thermal drift error occurs within a few minutes of operation. Owing to tooling problems of the high-speed spindle, axial offset errors also appear on the machined surfaces. If-then rules and thermal mode approaches are applied to remove defects of the machined surfaces. An infinite impulse response filter is used to compensate for surface roughness of the machine surface. A personal-computer-based error compensation scheme has been developed for the real-time thermal error compensation. Compensation interval of the developed compensator is selected to satisfy correction requirement of thermal errors of the HSMT. Experimental results confirm the validity of the developed compensator and show that the accuracy of machined surface is dramatically improved.