Error Compensation For Mold Corner Machining Based On Milling Force Prediction

Complex shape and high precision of surface are the main feature ofautomotive mold covering parts. Cavity corner, as one of the typicalcharacteristics of mold, results obvious deformation in the tool systems in theprocess of machining, which is because of milling load mutation generating bythe changing of radial cutting depth and angle of contact angle, and the materialof automotive mold covering parts is die steel, it has high strength and hardness.These seriously impact on the machining accuracy for automotive mold coveringparts.This thesis adopts fillet milling cutter for machining the cavity corner, filletmilling cutter will obtain the higher machining accuracy than the the ball millingcutter, which has the machining characteristic of point contact and narrow rowprocessing when machining corner, to the problem of low accuracy of sizeprecision for cavity corner, a detailed description of the corner machininggeometric relation between the cutting tools and workpieces is come up, and themilling force prediction model of the corner milling is established, thedeformation of tool systems generated by the milling forces is analyzed, surfaceerror model is established and compensates for the error to improve the surfaceaccuracy of the surface.Through analysis of the geometric position relationship between the tools andworkpiece during the corner machining, mathematical expressions of contactangle corner, contact zone between the tool and workpiece and the instantaneouschip thickness model which is based on cutting edge real tracks in the machiningprocess is obtained. To verify the accuracy of the proposed model ofinstantaneous chip thickness，the comparision of the model based on cuttingedge real tracks and the classical one is carried out.The establishment of the milling force theoretical model is generated byinstantaneous rigid force model of Altintas and the conversion matrix between all Coordinates about the characteristic of the corner, with the help of Matlabsoftware, the simulation of milling force is realized, the corner millingexperiments is completed and the accuracy of the model by analyzingcomparison between the results of experiment and simulation results is validated.In corner machining process, the bending deformation caused by the millingforce of the cutting tool systems is the main factor of affecting the accuracy ofmachined surface. Flexible model of milling force is established by analysing ofdeformation of the fillet milling cutter in milling process, using the method ofcombining the equivalent cantilever beam with finite element to builddeformation model, and tool deflection feedback between the deflection of thetools and instantaneous chip thickness is analysed.The corner machining process error is analyzed, according to the deformationmodel of the tool systems, surface error model of corner machining process isestablished, and the offline error compensation algorithm is put forward.Compensate each cutter location by iterative operation, and verify availabilitythrough experiments on the comparison between the surface before thecompensation and the one after the compensation.