Geometric Error Identification And Compensation Of Large-scale Gantry Five-face Machining Center Based On SAPSO-LM

The processing accuracy of CNC machine tools is the most important and direct factor that directly affects the quality of products.Improving the processing accuracy of machine tools is the top priority of the company’s further development.Geometric errors and thermal errors are the main factors affecting the processing accuracy of machine tools.In this paper,based on the largescale gantry five-face machining center,and the geometric error model of the machine tool,the geometric error coefficient of the machine tool,the geometric error of the machine tool and the experimental verification are studied.The geometric error model of the machine tool is established by analyzing the motion relationship between each parts of the machine tool,and the geometric error compensation algorithm is proposed for the geometric error model.Using the offline compensation method,the error compensation program is programmed to compensate the NC code.The experiment was verified by the Ball-bar QC20.The main research contents are as follows:(1)Establish a geometric error model for large-scale gantry five-face machining.Firstly,the geometric error elements of the large-scale gantry five-face machining center are analyzed.Based on the multi-body system theory,the topological structure analysis of the machine tool is carried out.The homogeneous coordinate transformation of the machine tool under the actual situation is completely and accurately represented,and the geometric error model of the machine tool is established.(2)Geometric error identification of large gantry five-face machining center.Aiming at the geometric error model which has been established,the SAPSO-LM algorithm is proposed.The hybrid algorithm component uses the group search ability of the particle swarm algorithm.The simulated annealing algorithm has the ability of probabilistic leap in the search process,which can effectively avoid local miniaturization and local fine search ability of LM algorithm in the search process.(3)Establish a geometric error compensation algorithm for the large gantry five-face machining center.On the basis of establishing the geometric error model and identifying the error elements,the geometric error compensation model of the machine tool is established,and the corresponding error compensation program is written,and the NC code of the machine tool is off-line compensated by the program already written.(4)Experimental verification of the machine tool error compensation model.Firstly,the geometric error of the machine tool is identified by the simple particle swarm optimization algorithm.Then the simplex particle swarm algorithm data and SAPSO-LM algorithm data are substituted into the above geometric error compensation model,and then the Ball-bar instrument is used to measure the machine error data before and after the error compensation.By comparing and analyzing the effects before and after compensation,the validity of the error compensation model is verified.(5)Experimental verification and software development.The compensated CNC command is imported into the large gantry five-sided machining center to compare the effects before and after compensation.The geometric error identification and compensation system of the machining center is established by using MATLAB,which is convenient for quickly obtaining the geometric error coefficient and geometric error compensation procedure of the machine tool.