Experimental Study On The Influence Of Environmental Temperature And Working Condition On Heavy Type Machine Tool Thermal Characteristics

Heavy type machine tool is one of the most important CNC equipments, which canbe used for the industries of aerospace, national defense military industry andtransportation etc. Heavy machine tool has its own characteristics, for example theworkpiece is complicated and big, the load changes dramaticlly and the range is large.Because of these characteristics, heavy machine tool is easily influenced by theenvironment and the working condition factors, which will lead to much spindle thermalerror in the running, and the machining accuracy of machine tool will be reduced.Therefore, this thesis took the Heavy Gantry CNC Milling Machine as the research object,and surrounded “the experimental research of environmental temperature and workingconditions influencing heavy machine tool thermal characteristics”. According to theanalysis of thermal characteristics experiment of environment temperature and differentworking conditions, the multiple linear regression thermal error model with robustly wasestablished. The application of compensation was realized in the Heavy Gantry CNCMilling Machine XHC5735based on thermal compensation model embedded in Siemens840D CNC system. The main contents are:Firstly, based on the basic theory of machine tools thermal characteristics andstructural characteristics of heavy machine tool，the different types of spindle thermaldeformation were analyzed, and the ambient temperature and working conditions factorswere mainly studied.Secondly, using the arrangement method of the measuring points at the vertical andhorizontal directions, the temperature field distribution of heavy type machine tool wasmeasured. At the same time，by the five points method the thermal deformation of spindleterminal was measured under the state where machine tool was not running. The spaceenvironment temperature distribution rule in the vertical and horizontal direction and theinfluence which works on the thermal deformation of spindle terminal were researched.Afterwards, experiments were carried out under the working condition of varioustypes of spindle thermal characteristics. Then by the research of the influence of oil filmthickness, different spindle speeds and beam positions on the thermal deformation of thespindle terminal, the variation of the film thickness effects on the thermal deformation ofspindle was excluded, and the great effects of spindle speed and beam position on thespindle terminal thermal deformation in all directions were also proved.Finally, on the basis of the above research, according to the thermal key pointselection principle of main factors strategy and uncorrelated strategy, the optimalmeasuring points were selected. Based on multiple linear regression modeling, the model was established, and the number of the model variables was optimized. It was found thatwhen only had the environment and ram two measuring point variables, the fitting effectwas best. The compensation system hardware was connected based on840D CNC system,the compensation model was embedded in the840D CNC system. Through the PLCprogram design, thermal compensation function was achieved. By doing the compensationexperiment on experimental verification in the Heavy Gantry CNC Milling MachineXHC5735, thermal error reduced to less than15μm by35μm, and the compensationeffect was up to65%.