Improvement of positioning accuracy by real-time compensation of thermal elongation of ball-screw (2nd report) - Compensation for Zero positioning error under room temperature change

This paper deals with the improvement for Zero positioning error of machine tool element under room temperature change. During operation the temperature at fifteen positions of the hollow ball-screw is measured and input into the personal computer by the optical telemeter system. Based upon the temperature distribution of ball-screw, the present position of ball-screw nut obtained from CNC controller and the information of initial positioning error, the compensating quantity for Zero positioning error is calculated. The compensating quantity is fed from the PC to CNC controller, and the origin shift of machine coordinate is immediately executed. These measurement and control are repeatedly executed during operation, and the real-time compensation is realized. Only once the measurement of initial positioning error is needed. It is clarified that the positioning error of ·8.4-+1.5 μ m is realized under room temperature change of 16.5-26.5°C during 23.5hr operation.