The Research On Evaluation Method Of Assembly Quality For Linear Feed System Of Machine Tool

The assembly quality of NC machine tools is the key factor affecting the quality of CNC machine tools,and the quality of assembly determines the machining performance of NC machine tools to a great extent.The assembly error of machine tool linear feed system will cause the movement loss of precision,accelerated wear and worktable position fluctuations,which affect the dynamic performance of the feed system seriously.Therefore,the research on evaluation of assembly quality of the linear feed system has important significance.In this paper,the method of rapid evaluation of assembly quality of linear feed system is studied,and the main research work is as follows:(1)through the analysis on the system dynamics theory,this paper establishes the mathematical model of the transmit motion of linear feed system,and by simplifing the model according to the physical parameters of self-made experimental platform,this paper finally get the identification function of the damping coefficient.(2)by analyzing the influence of the assembly error of linear feed system on damping coefficient,a method of evaluating the coaxiality error of motor and screw is proposed by using the periodic signal characteristic of damping coefficient.(3)through the analysis of the influencing factors on feeding precision of linear feed system,the method of evaluating the coaxiality error of motor and lead screw is put forward based on the periodic signal characteristic of the tracking error(the encoder is mounted on the screw shaft);a method to evaluate the parallel error of a lead screw by means of the cumulative component of the tracking error is presented.(4)through the decomposition of the relative horizontal attitude of the rail,several typical relative positions of the guideway are established,and the method of directly measuring the parallel degree of the guide rail is given on the basis of the synchronous measuring device.(5)the experimental results show that the evaluation methods of assemblingquality presented in this paper can accurately reflect the assembly problems in the assembly process of the linear feeding system.The evaluation methods proposed in this paper are convenient for analyzing and evaluating the assembling error of feed system by extracting different feature system parameters in the dynamic process of machine tool.compared with the traditional method which is relied on machine tool inspection gauge tools for assembly evaluation in the stationary state,this method is more convenient and efficient.