Research On Machining Error Analysis Of Hardened Steel Free-form Die Based On Curvature Feature

With the rapid development of China’s automobile industry,people have put forward higher requirements on the appearance of automobiles,so automobile exterior covers with free-form surfaces have become more and more widely used.It is obtained through the stamping process from the automobile outer cover,so it is extremely important to produce precision free-form molds.In the process of processing free-form surface molds,due to the change in curvature,cutter error,milling vibration and residual height are generated during milling.These two processing errors will cause the precision of the surface of the mold to be reduced.Therefore,it is necessary to study the milling freedom of ball-end mills.The milling rule of curved dies provides a theoretical basis for the improvement of the surface quality of the dies,and at the same time plays an important role in improving the precision of the dies and the processing efficiency.Taking the automobile outer cover mold as the research object,the influence of the curvature characteristics of the free-form mold on the milling processing errors is analyzed.The specific research contents include:Based on the curvature change and Gaussian curvature of the free-form mold,a comprehensive curvature feature die of the free-form surface considering the principal curvature in two directions is constructed.The influence of the curvature characteristics on the contact parameters between the tool and the workpiece during the milling process is analyzed,the instantaneous milling force die considering the curvature characteristics is established,the micro-element milling force die is established,and the overall milling force die is established by integration.Analyze the yielding error,milling vibration and residual height during the milling process,and establish a machining error die for each error.According to the spatio-temporal characteristics of various machining errors,a comprehensive machining error die that takes into account tool error,milling vibration,and residual height is considered.Extraction of the detected points on the machined measuring equipment and through the adaptive sampling method,Adaptive surface subdivision is used to obtain the processing error curve of the free-form mold,and the wavelet decomposition of the processing error curve is used to obtain the Detected detection points with significant processing errors.Through the experiment of milling free-form mold by machining center,select a set of machining parameters to ensure machining accuracy and efficiency.Based on this set of parameters,verify the accuracy of the milling force die and the comprehensive machining error die.