Research On Thermal Displacement Modeling And Compensation Technology Of CNC Machine Tools

As the manufacturing industry changes,the precision and stability of equipment are more and more concerned by customers.CNC machine tools not only require high machining accuracy,but also to maintain stability,is an important point for manufacturers to customers.In numerical control equipment processing,the above characteristics of the machine tool is particularly important.For the mechanical structure,there are geometric errors in the machine tool casting and the installation process,which can hardly be eliminated in the production process.The workpiece in the process of cutting tool and machining workpiece under the action of cutting force of its Angle and straightness will have deviation,resulting in the processing program program specified position and the actual position will have error,resulting in the workpiece size out of tolerance,resulting in errors in processing.Thermal error caused by the Angle of the machine tool structure and deformation of the workpiece straightness deviation,the characteristics of the position error or contour and surface compared with the former two kinds of error,it is easier to be ignored,in a lot of researchers and scholars study shows that in the total error,occupy 40%? 70%,thermal error in numerical control machine tool processing,cannot guarantee machining accuracy,easy create batch workpiece scrap,eliminate thermal error,It is the main task to improve the stability of machine tools.The basic method of error prevention and error compensation is to make machining stable.For the error prevention method,it can be corrected in the design and installation process of constant temperature workshop and machine tool.The construction cost of constant temperature workshop is high,but customers rarely use it.The assembly technology is now very perfect,but the body structure costs manpower and material resources in fine grinding,especially for small and medium-sized manufacturers.Early research cost some larger error compensation method,but as a technical reserves,compared with error prevention method can save more economic and time,and later have measured temperature of key points and modeling,improve the robustness,on the basis of real-time real-time compensation model using numerical control machine tool system programming,there will be investment in the economy under the condition of small feedback to good effect,relatively easy operability.However,in practice,thermal error compensation for temperature detection and real-time compensation has been difficult to achieve,because of the wide distribution of heat sources,CNC machine tool itself complex structure,many parts,the thermal expansion coefficient of materials are not the same,the temperature change will change with time and space,and the temperature field is a nonlinear function.The research object of this paper is mainly VMC-85 vertical machining center produced by the company.The thermal error leads to deviation of displacement bias on the contour and surface of the workpiece.The essence of the error compensation method is to reduce or eliminate the thermal displacement deviation,improve the machining accuracy of VMC-85 models,and meet the needs of customers for VMC-85 models.The main research contents of the project are as follows:(1)Refer to domestic and foreign literatures and analyze the research status of thermal error.Propose the problem and the solution,design the thermal error modeling and the compensation technical process,practice the numerical control machine tool in this model thermal error compensation.(2)The VMC-85 model optical machine structure and the characteristics of the whole product and the distribution of heat source,analysis of the influence of the accuracy of the CNC machine heat source,reasonable distribution of temperature sensor installation position,find out the key heat source point,discuss the temperature difference measurement method,collect key point temperature data and displacement deviation data experiment.(3)the selection of temperature sensor,laser interferometer,through the instrument of thermal error data collection.On the basis of collecting the data of thermal error and using the artificial neural network technology,the thermal error modeling of VMC-85 model shaft was established based on BP neural network,and Propose optimization scheme.(4)Establish BP thermal error model for VMC-85 model to carry out robustness simulation analysis,influence on thermal error under different working conditions,and analysis of temperature measuring point position deviation.By analyzing the simulation results,changing the temperature measuring points to adapt to different working conditions and environments,improving the robustness of the model and improving thermal error modeling.(5)According to the established model,the developed PMC programming system of FANUC system is used to communicate with the numerical control system and the external temperature measuring point,and the displacement deviation caused by the temperature change is compensated in real time to improve the accuracy and stability of the machine tool.