Measurement and Compensation Backlash Error for A Five-Axis Machine Tool by Computer Numerical Control

A portable high-precision backlash error detection module was developed for machine tool rotary axes using an embedded chip. The system consisted of an MCU module, photoelectric switches, a BT40 tool holder, and an industrial PC. Tiny time variations with different backlash errors were measured by the system with a time resolution of 4 $\mu$s and a repeatability accuracy of 10 $\mu$s. As a result, the calibration gain between the magnitude of the backlash error and the variation in time was determined successfully. Through the gain, the measurable time variation was converted into the backlash value. The value obtained after the conversion was used to calculate the compensation value. Finally, the backlash compensation value was applied to the machine tool controller using the software. The experimental results indicated that the repeatability accuracy of the system for the rotary axes was approximately 1/100° with an estimated measurement range of 0.05°. This method effectively improved the maintenance downtime. Compensation time was reduced by 50% and minimized to less than 10 minutes.