ZHANG Liping1, LI Yenong1, ZHAO Jianjie2

（1.School of Mechanical Engineering, Nantong Vocational University, Nantong 226007, China;
2.Nantong Technology Investment Group Co., Ltd., Nantong 226007, China）

Abstract: In order to establish the mathematical model between the best maintenance periods and the effective degrees on the machining center, the best maintenance period was determined. Through analyzing the causes and types of common fault of the vertical machining center, curve between the average failure rate and a predetermined time was established. For this type of machining center can be repaired, the average failure rate increases gradually over time increased. Time interval model between preventive maintenance and breakdown maintenance was established, this is based on reliability and maintainability. Based on the average failure rate function is an increasing function, the best maintenance periods may be determined when the effective degrees was maximum. And by way of example, the best maintenance period of machining centers was calculated by using numerical integration method of reliability function. The results show that this method of calculation to provide an effective way for determining the best maintenance period CNC machine tools.

Key words: machining center; reliability; average failure rate; maintenance; effective degrees; preventive maintenance period