On-Machine Measurement Of Machining Error Method Research Based On Mould Surface Adaptive Sampling

With the rapid development of automobile cover mould,aerospace manufacturing,application of parts having a free surface feature has become more and more widely,while the machining accuracy requirements are becoming increasingly stringent.Therefore,on-machine measurement of free-form surface machining error to improve the machining accuracy control has a very important significance.Firstly,based on the principle of the center of gravity established mould surface adaptive sampling model,on the basis of the curve curvature bending model,principal curvature RMS curvature bending model,Gauss curvature bending model analysis.Based on the sampling points from the most adaptable Gauss curvature established shape function,analysis the rectangular grid topology of paraboloid model,and adjust the grid spacing by controlling factor,arranged parabolic model surface adaptive sampling points.Then,on-machine measurement technology is proposed based on the adaptive sampling and the reconstruction of NURBS control points,the method is in the case of less sampling point,combined with NURBS surface control point reconstruction theory,calculate the control point of mold theory surfaces,by adjusting the control points of the theory surfaces,so that the accuracy of NURBS surfaces reconstruction based on adaptive sampling points increased by 10%.In this paper,use form and position errors are no benchmarks surface profile error,evaluation the normal machining errors of mold surface,based on generalized Newton optimization algorithm,compute the minimum distance between actual process of after surface reconstruction and initial design and experimental surface then get the machining error of actual mould surface.Finally,on-machine measurement methods of machining error based on surface adaptive sampling and reconstruction were studied experimentally.In the experiment,respectively,on-machine measurement of automobile outer cover mould use the adaptive sampling method and equal arc length sampling method,and compared with the measurement results of coordinate measuring machine,experimental results show,adaptive sampling algorithm is applicable to the steep face of the on-machine measuring of machining error,error distribution of onmachine measurement of mould model coincide with coordinate measuring machine measurement,it also proved that the on-machine measurement of machining error in this paper has better feasibility.