Research On Thermal Errors Inspection And Compensation Techniques Of NC Machine Tools

When a NC machining tool is working, the parts of machine tool are inflluenced by the fators, such as frictional heatcutting heat and envirenment temperature, etc. so the temperature rises. The correct position between tool and work is destroyed, and the accuracy of machine tools is come down, so the thermal error comes.into being. In the process of precise maching, the thermal error of the mechanical process system covers 40-70% of the total machine errror, the thermal deformation has become the major error in precision and extra-precision machine.The main research theme of this dissertation is sensor placement optimization,setting-up of the thermal error compensation model and development of the on-line temperature measurement system in thermal error compensation of NC machine tools. Based on the fully understanding and deeply analyzing the reason and mechanism of the thermal error for a certain type of CNC machine tools, the theory of optimization for the sensor location is recommended, the multivariate linear regression modeling theory is recommended, some new methods are used to make the optimization of the sensor location in the thermal error modeling, we also developed an embedded numerical temperature on-line measurement system. Then, the experiments of thermal error measurement and compensation for a certain type of tools are carried on. The main contents of the thesis are as follows:1. The background and significance of the research are stated. The research history and present status of the thermal error modeling are also provided. Then, the thermal dynamic process of NC machine tools is analyzed, the principle and method of thermal error compensation are introduced.2. The structure of spindle box and conducting heat situation are studied. On the basis of research, the method measuring thermal error is expounded. That is measuring thermal error value by five-point measurement, and measuring the spindle box's temperature value by sensor.3. The theory of optimization for the sensor location is recommended, the fuzzy group and correlation analysis are make used of to optimize the key temperature measurement points in spindle box of the machine tools, and the most appropriate points are located. The method of setting up machine tools thermal error model is recommended. The thermal error model is established by use of multivariate linear regression for the machine tool the experiment used.4. The system that measures temperature on-line is set up. It can measure the key points' temperature on-line timely. The thermal error compensation model is set up.The experimental results have proved that the methods optimizing for the sensor location and thermal error modeling compensation methods were feasible and valid.