Cumulative Analysis And Tolerance Control Of Space Error Of CNC Milling Machine

In order to ensure the quality of machined products,one of the important preconditions is to ensure the machining accuracy of target machine tools.In actual machining,the machine tool will be affected by many error factors,and finally lead to the machine tool output accuracy out of tolerance.Therefore,it is an important way to improve the machining accuracy to systematically analyze the influence degree and variation rule of these error factors on the accuracy of machine tools and take reasonable measures to control them.Based on the analysis of the research status of machine tool error modeling and analysis and machine tool error control at home and abroad,this paper puts forward the subject of "cumulative analysis and tolerance control of spatial error of NC milling machine".Firstly,this paper establishes a relatively perfect representation method of machine tool output error,and takes vmc-850 three-axis NC milling machine as the research object to carry out error modeling and error analysis.Finally,according to the action law of component unit error on machine tool output error,this paper explores a more efficient control strategy and method of machine tool(tool)attitude error.The main research contents of this paper are as follows:1)A relatively perfect representation method of machine tool output error is established,which includes the position error of the tool relative to the workpiece and the attitude error of the tool relative to the workpiece;In this representation mode,the error model of the target machine tool is established by using the theory of multi-body system and the principle of homogeneous coordinate transformation.The model includes the spatial position error and spatial attitude error of the machine tool,which provides technical support for the subsequent analysis of component unit error and the prediction of tolerance control effect.2)Using the machine tool error model established,the action law of single error source is analyzed firstly,that is,the effect results and law of 30 element errors contained in the machine tool component on the output error of the machine tool are analyzed.On this basis,the cumulative action law of multiple error sources,including single component error sources and multi-component error sources,is deeply studied,and their analysis methods and steps are given.The maximum value of tool position error and tool pose error under different error input sources is obtained,which represents the relationship between tool and workpiece.The actual and ideal pose of the tool in the workpiece coordinate system are given,which provides direction basis for error control.3)In order to effectively control the tool attitude error,a machine tool attitude error control method based on the prediction of tolerance control effect is proposed.Using MATLAB software to randomly generate the value of degree of freedom variable in the tolerance region of each component tolerance item,obtain the change matrix of the pose of each relevant component,and obtain the change range of the pose of the tool corresponding to each tolerance item relative to the workpiece through the error model,that is,the mapping relationship between the tolerance item and the output error of the machine tool;The cumulative effect of multiple tolerance items is analyzed.Finally,taking the partial tolerance project control of vmc-850 three-axis NC milling machine as an example,an analysis example is given to control the tool attitude error of the machine tool,so as to greatly improve the efficiency of tolerance design and adjustment of the machine tool.