Research On Outer Race Elliptical Groove Grinding With Basin-like Grinding Wheel

The outer race of constant universal velocity joint (CVJ) is one of the most important components of vehicles, and its inner spherical surface has axially arc grooves or axially straight grooves with elliptical section, whose material is steel 55. At present, the finger-like grinding wheel is widely used to approximately grind elliptical groove in many manufacturers of CVJ, but the theoretical error of this method is large. In order to decrease the error, a novel grinding method with basin-like grinding wheel is proposed in this dissertation. Then the dissertation establishes the mathematical model, optimizes the parameters by means of simulating elliptical arc, restrictive random direction method and simplex method respectively. The results of simulation for a kind of elliptical groove ground by basin-like grinding wheel indicate that the maximum theoretical error will be reduced to 0.631μm, which is less than the resolution of grinding wheel axial motion of outer race ball track grinding machine.Refer to the different grinding characteristics between straight grooves and arc grooves, the dissertation focus on the grinding process of elliptical groove grinding machine, fixes the cutter setting position, establishes the simulation system of CNC outer race ball track grinding machine by Pro/ Engineer, and analyses the influence of dressing quantity on the cutter setting position of CBN basin-like grinding wheel in different elliptical groove grinding machine.The grinding experiments of arc grooves and straight grooves with the basin-like grinding wheel were completed ,and the measurements of the grooves by portable arm coordinate measuring machine were carried out, which validates the feasiblity of this grinding technology.In order to calculate the grinding force of the basin-like grinding wheel in grinding outer race elliptical grooves, the dissertation simplifies the grinding process as follow: the evenly distributed abrasive grains move around grinding wheel axis along an imaginary ellipse at high speed, while the imaginary ellipse moves along the trace deflected from the grinding wheel axis simultaneously.Simplifying the geometric shape of abrasive grains as cone-shape, the dissertation studies the grinding force models both of the cut-in phase and stable phase in profile grinding with axial feed in detail on the assumption that the first circuit abrasive grit of grinding wheel took part in the grinding process; According to the experiments of inter-grain spacing measures and surface grinding of steel 55 with CBN grinding wheel,optimizes the parameters of universal calculation model of grinding force based on undeformed chip thickness by restrictive random direction method, obtains the parameters of the CBN grinding wheel, then presents the optimum fitting equations of unit grinding force in grinding steel 55 with CBN grinding wheel; According to the experimental results for axial feed grinding of steel 55 with CBN grinding wheel, validates and analyses the grinding force model of profile grinding with axial feed.The analysis of grinding force in CVJ outer race elliptical groove grinding with basin-like grinding wheel reveals that, the grinding force will be decreased and the surface quality will be improved, if wheel velocity increased and feed velocity decreased. On the other hand, the grinding force of basin-like grinding wheel will be increased but the grinding remain height and the grinding force of abrasive grit will be decreased with the decrease of inter-grain spacing. Therefore, on the premise of guaranting surface quality, the grinding method of using bigger inter-grain spacing can reduce grinding power.At last, the dissertation further validates the grinding force models of surface grinding and profile grinding with axial feed by finite element simulation analysis of unit abrasive grit using Deform-3D.