Running state detection and performance evaluation method for feed mechanism of numerical control machine

Due to the enclosed construction and real-time servo control, it is difficult to detect and evaluate the running state of numerical control (NC) machine feed mechanism. In this paper, the motor torque, which is provided by open NCs, is used to analyze the operating performance of feed mechanism. The torque data is divided into segments in different feed condition and piecewise resolved into long-term trend and short-term fluctuation by the least square method. Features of trend and fluctuation are used to indicate the operating condition and mechanical performance. The proposed method is evaluated by three typical feed mechanisms, i.e. rack & pinion, ball-screw and ball-screw with balance hydraulic cylinder, in a large scale milling and boring machine. Results show that the running state of feed mechanisms can be effectively evaluated and some installed and structural defects are well identified.