Machining, Measurement, and Control Laboratory

The Improvement of Motion Accuracy of Hexapod Type Machine Tools and Its Machining Performance
Masao Nakagawa (Okuma Corp.)
Tetsuya Matsushita (Okuma Corp.)
Shigeharu Watanabe (Okuma Corp.)
Yoshiaki Kakino (Kyoto University)
Yukitoshi Ihara (Osaka Institute of Technology)

This paper describes a method to calibrate the kinematic parameters for Hexapod-type machine tools by using a telescoping ball bar device. The proposed calibration method deals with the length error of struts, positional errors of base and platform joints as kinematic parameters. The parameter calibration is performed on a commercial Hexapod-type machine tool based on DBB measurements. As a result, the out-of-roundness error is reduced from 16 mm to 6 mm. Cutting tests are also conducted to confirm the machining accuracy and the productivity of the Hexapod-type machine tool in the machining of an aluminum alloy disk and an automatic transmission case of a car, which has many holes, threads and inclined oil holes. By using the Hexapod-type machine tool, the productivity is improved by about 30% in the machining of the automatic transmission case of a car, compared to the case where a trunnion-type five-axis machine tool is used.