Thermal Error Measuement And Compensation Of Cnc Machine Tools

The thermal error of CNC machine tools is a main error in the precision and ultra-precision machining. The thermal error compensation is an economical and effective method to reduce thermal error and improve the machine tool precision. In this dissertation, temperature and thermal error measurement system, analysis system used for temperature measurement points optimization and thermal error modeling, device for thermal error compensation are designed and developed.The measurement system's hardware was based on temperature sensors, displacement sensors and PCI data acquisition card; signal processing circuit was developed to conversion and filter of analog signals. System's software was based on LabVIEW language; the whole operation rate of data acquisition program was enhanced by using local circulation cache technology and thirty-two channels of single can be acquired simultaneously. The measurement system consisted of parameter setting, test conditions, continuous acquisition, data saving and data observe five functional modules.According to that too much temperature points were chosen when traditional grouping optimization was used in several directions, multi-direction temperature points optimization was presented. Thermal error was modeling by multiple linear regression based on least square and RBF neural network. In order to reduce the time of points optimization and modeling, an optimizing and modeling system was developed by MATLAB.The device used for thermal error compensating was based on DSP and A/D, and the interface circuit was developed based on the theory of optical coupling isolation. Thermal error was calculated according to temperature signal and thermal error model; then it was transmitted by setting CNC parameter and PMC program; thermal error was compensated by external coordinate system shift.The temperature and thermal error measurement system, points optimization and thermal error modeling analysis system, real-time thermal error compensation device were used on MCH63 horizontal machining center. The temperature points used for modeling and thermal error model were obtained, and thermal error was compensated. The result indicated that the device could compensate the thermal error and the thermal error was decreased.