Simulation And Experimental Study Of Machined Surface Topography Based On NURBS Surface Reconstruction

The hardened steel has been widely used in automotive mold processing and other fields for its high strength that good thermal stability and excellent abrasion resistance.Meanwhile because of the complexity and smoothness of the automotive panel dies,the hardened steel processing quality is extremely stricted.So this paper takes the surface quality of Cr12 Mo V mould steel sample as the research object,and expand the following research for the surface topography obtained by milling.Firstly,establish the milling geometric model of ball end milling cutter.Analyze the formation of surface topography.Discrete milling edge as micro unit and get discrete points,describe their static and dynamic state.Obtaine discrete point trajectory under cutter interpolation motion and machining inclination influence.Transform the tool coordinate system to the workpiece coordinate system.Obtaine the discrete point trajectory equation and the matrix equation.Secondly,describe mathematically workpiece free surface based on NURBS curve.Analyze the principle and process of three kinds fitting discrete points reconstruction methods.Extract discrete points of the edge line and determine whether them are involved in cutting motion,Finally,adoptting the reconstruction method of repositioning surface control points,the simulation process of surface topography reconstruction based on NURBS surface control points is completed by fitting discrete points of blade edge and adjusting setting control points.Then,complete the tool cutting movement trajectory correction.The effect on surface topography simulation is studied for row spacing,feed per tooth,cutting depth,processing speed,processing angle and the curvature of the surface.Analyze qualitatively and quantitatively the surface topography simulation by means of feed direction residual height,3D surface ten point height and surface roughness deviation from the arithmetic mean of reference datum,Analysis shows the influence of feeding direction curvature on the surface morphology than the curvature of the row direction.This is due to the change of the curvature of the feed direction is easy to initiate interference,resulting in higher residual height.Finally,study milling surface topography on Cr12 Mo V die steel samples based on experimental method.and the quantitative analysis is given from the view of roughness.Verify the influence rules of surface topography simulation.This paper has a certain reference value for obtaining the high quality surface for ball end milling cutter machining hardened steel.