Error Modeling And Prediction Of Remanufacturing Machine Tool Assembly Process

With the continuous deepening of the national green development concept,machine tool remanufacturing has become the best way for green treatment of used machine tools.Because the number of waste machine tools in China is huge and is gradually entering a centralized phase-out period,and the assembly process is the key to affect the quality of remanufacturing machine tools,it is of great significance to study the assembly process of remanufacturing machine tools.There is an error transmission,coupling and upheaval in the assembly process of the remanufacturing machine tool.The assembly error is greatly uncertain due to the influence of many factors,which can easily lead to the reassembly of the assembly without meeting the requirements.In order to improve the success rate of primary assembly of remanufactured machine tools,it is urgent to predict the final assembly error.Based on this,this topic takes the assembly process of CAK6150 remanufacturing CNC lathe as the research object.Based on the theory and technology of error transfer coupling mechanism and quality prediction in the assembly process,this topic conducts the error modeling and prediction of the remanufacturing machine tool.The main research contents are as follows:(1)Aiming at the problems of diversified and unstable quality of remanufactured machine parts and dynamic,multi-dimensional,coupling and dramatic variability of assembly quality,an error characterization method of remanufactured machine parts based on small displacement screw method and error evaluation is proposed.In this method,the point cloud obtained by detecting the feature surface of the part is fitted and the fitting surface is geometrically analyzed to obtain the small displacement spinor value of the feature surface of the part,so as to realize the more accurate error representation of remanufactured parts and reusable parts,and provide a theoretical basis for the error transmission analysis of the assembly process of remanufactured machine tools.(2)Aiming at the problems that the simplification of parallel node into serial node of remanufacturing machine tool assembly has a great impact on the calculation error transmission,and the traditional error transmission model is not completely suitable for remanufacturing machine tool,an error transmission model of remanufacturing machine tool assembly process based on Jacobian spinor method is established.On the basis of considering the load deformation of remanufactured parts and reusable parts,the series parallel assembly in the assembly process of remanufactured machine tools is analyzed,and the coupled small displacement screw is calculated.The small displacement screw value of the final feature is obtained by Jacobian screw method,so as to realize the prediction of the final assembly error of remanufactured machine tools.(3)Aiming at the problems of unstable assembly quality caused by drastic error changes in the assembly and adjustment process of remanufacturing machine tools,an optimization model of assembly and adjustment of remanufacturing machine tools considering adjustment man hours and assembly quality is established.The model weights the adjustment difficulty of different characteristics based on the fuzzy AHP method,and designs the solution program through the optimal control theory.Finally,the optimal adjustment scheme of the assembly process of remanufacturing machine tool with shorter adjustment man hours and less assembly error of remanufacturing machine tool after adjustment is obtained,so as to improve the success rate of one-time assembly of remanufacturing machine tool.