The Research On Planar Cam And Noncircular Prats Parametric Cnc Grinding

According to the characteristics of the MK250 cam grinder NC machining in the polar coordinates, the research on Planar cam and noncircular parts parametric CNC grinding is the focus in this paper. It is carried out on the base of deep analysis of domestic and foreign research status.First,this paper analyzes the planar cam according to its kinematics theory.Based on the reverse theory of cam,I deduce accurately working contour equation and tool center track of the translating roller cam.At the same time I infers the mathematical model of the constant speed grinding in the polar coordinates.And then,this paper adopts the software of Visual C++ 6.0,and develops CAD/CAM system of the Planar cam,which can achieve the cam's contour designing, tool center track calculation,parameter judging, interpolation error control.with the CAD/CAM system, it can also output the NC machine code. The CAD/CAM system of the Planar cam which is integrated with CNC system of the MK250 grinder is verified its correctness.Once more,this paper adopts vector method to solve tool center track of noncircular parts, and designs another set of software,which can achieve the automatic programming of noncircular parts that are composed of straight line segment and arcs.It realizes the partial C cutting tool radius compensation and outputs the NC machine code. This software is also verified its correctness on the MK250 cam grinder.Finally,based on the characteristics of NC machining in the polar coordinate and in the rectangular coordinate, the interpolation error models in the polar coordinate and in the rectangular coordinate are respectively established.By the programming language VC++, detailed error curve with example is done by the.software of MATLAB. Compared with the linear interpolation error in the rectangular coordinate, the polar-coordinate NC grinding cam results a almost 31% decrease in error ratio. the factors such as the step of Polar angle, the planar cam law of motion, the planar cam base radius, the planar cam rise and down stroke angle, the stoke, grinding wheel radius are discussed to analyze the interpolation error's influence. On the basis of that analysis,three conclusions are obtained. First,the interpolation error could be controlled within a small range by the division polar angle,additionally,as the polar angle step becomes small,the programming error nonlinearly decreases Secondly, planar cam law of motion impacts the trends of interpolation error curves, At last, selecting a larger base circle radius, a smaller stroke, a larger rise or down stroke angle can reduce the interpolation error.