| Studies show that the thermal error is the main source of the CNC's error. The thermal deformation error makes up of 40%～70% of total manufacture error in precision and super-precision manufacturing, and it becomes the greatest obstacle which restricts the precision of the machine tool. High-speed and superhigh-speed CNC machine tool, which equipped with high-speed motorized spindle, the motorized spindle thermal error seems particularly outstanding, makes up of 60%～80% of total manufacture error in parts.With the support of the Important National Science & Technology Specific Projects:"Dynamic comprehensive error compensation technology of precision CNC machine tool", the paper studied at the high-speed spindle thermal error parameter identification, error modeling and compensation system. The main work is as follows:(1) With the spindle for research object, the paper has done detailed analysis of the spindle's structure, cooling way, and the main heat source. Based on the heat transfer, the heat source and cool conditions of the motorized spindle system is analyzed and calculated.(2) Based on the experimental data, the paper has done detailed analysis of the spindle's thermal error's non-linear characteristics. According to the non-linear modeling ability of the Artificial Neural Network, BP Neural Network thermal error modeling is been done adopting three kinds temperature variable.(3) Based on the principle of the BP Neural Network, a modeling method of BP Neural Network Genetic Algorithm(GA) optimization is proposed. Three thermal error models about the moterized spindle are established.(4) According to the requirement of the project, a data acquisition system of motorized spindle is built, based on PLC. Aimed at the FANUC 18i CNC system, a thermal error compensation system based on PMC, is developed based on the shift function of external coordinate theory. At the same time, a real-time thermal error compensation experimental of the spindle and a text cutting are carried out. |
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