Muti-Axis CNC Machining Accuracy Prediction And Machine Tool Parameter Optimization

Multi-axis CNC machine tools are the indispensable equipment for the aerospace advanced manufacturing,while the aerospace product brought higher requirements for the CNC machining accuracy.Multi-axis CNC machining accuracy prediction and machine tool parameters optimization is important to ensure the final machining accuracy of the part.The geometric error and servo error are the main factors to affect the machine tool accuracy.At present,the machine tool manufacture enterprise and the aerospace customers evaluate the relationship between the machine tool error and machining accuracy requirements mainly by experience.The customer product machining accuracy requirements oriented design and maintain capability of the machine tool manufacturing enterprise is deficient.And the aerospace manufacturing enterprise is lack of the capability of the part machining accuracy oriented machine tool choosing and maintained method.In order to address the issues mentioned above,the multi-axis CNC machining accuracy prediction and machine tool parameter optimization is researched in this dissertation.The main contributions of this dissertation are as follows:1)The method for three-axis machining error predicition method considering the machine tool geometric error is proposed.In order to address the issue of the prediction of part form and positional tolerance oriented CNC three axis machine tool machining accuracy,the machine tool geometric error based cutter posture error model is constructed.The tilt area of the machined geometry are evaluated by the cutter posture error.And the form and positional tolerance oriented machining accuracy are predicted.Then the relationship between the machine tool geometric error and the part machining error is established,and the machine tool accuracy improvement could be supported by the relationship.The prediction error of the method about the part within the flatness and cylindricity tolerance is not more than 10%,and the method is verified by the requirements of form and position tolerance of the aircraft structure parts.2)The method for five-axis machining error predicition method considering the machine tool geometric error is proposed.In order to address the issue of the five-axis machining accuracy prediction within the cutting position uncertainty which is caused by the machine tool geometric error in complex surface CNC machining,the complex surface five-axis end and flank milling cutting contact point calculation method considering the machine tool geometric constraints is given,and the complex surface machining accuracy prediction model is constructed.Then the relationship betweengeometric errors and the machining error in five-axis machining is constructed,and the optimization constraint based on the complex surface machining error is established.The prediction error of the method about the part with surface profile is 13.6%,and the method is verified by the requirements of the profile tolerance of the complex surface machined in the aero manufacture enterprise.3)The machining profile error oriented CNC machine tool servo parameter optimization method is proposed.In order to address the issue of effect of servo parameter to the machining profile accuracy when in different part shape condition,the cutting tool path of the machined part is taken as the representative of the part shape.The servo parameter oriented contour error prediction model is constructed to establish the optimization of the servo parameter.CNC acceleration-deceleration based tool path transformation to position and velocity algorithm is researched.The servo parameter oriented contour error prediction model is constructed to establish the optimization of the servo parameter.The experiment shows that the average profile accuarcy of the S part is improved about 19.9% after the servo parameters are optimized.The research of this dissertation is realised in the machining error prediction system developed.Some cases from the aero manufacturing industry areapplied to demonstration the advantage of the proposed method.