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Research on the speed change law of cam rotation during grinding

almost all the domestic non profiling CNC camshaft grinding machines are expensive imported equipment. In this paper, the CNC system and software of CNC camshaft grinder with PC as the control device and the data processing method of cam contour grinding under constant linear speed control are developed. Cam grinding is a special non-circular grinding. During grinding, the grinding conditions of other parts are constantly changing except that the grinding conditions of the base circle are the same as those of the outer circle. First of all, because the cam curve is composed of several simple or complex curves, it leads to the discontinuous movement of the cam contour and the sharp jump of speed and acceleration. Secondly, the instantaneous speed of the ground point, the contact arc length between the grinding wheel and the workpiece, and the polar coordinate position of the grinding point relative to the cam center all change with the shape of the cam curve, making the grinding force, the elastic deformation of the grinding wheel workpiece system, and the grinding heat also change constantly. To this end, the following process measures are adopted. Cubic spline function fitting is used for data processing in grinding process. The cubic spline function can maintain the continuity of the first and second derivatives at each type of value point, and the smooth connection between each type of value point, so that the cam lift curve changes continuously and smoothly, and the speed and acceleration in the grinding process transition smoothly. Adopt variable speed constant grinding rate control. Make the workpiece rotate differently at different grinding points, and the linear speed of the cam contour at the grinding point remains basically unchanged, so as to ensure that the metal grinding rate remains basically unchanged during the grinding of the cam for one week, and the grinding force changes little, so as to reduce the surface ripple and burn of the cam contour. Software compensation technology is adopted

I. before machining, input camshaft data (camshaft size, number of cams, lift table data, etc.), cam machining data (grinding allowance, grinding feed, etc.), grinding wheel data (grinding wheel dressing amount, grinding wheel dressing time interval, etc.), machine tool system parameters and other data as agreed, calculate the actual contour coordinates and grinding machining linkage coordinates of the cam, and then carry out constant grinding removal rate processing, After cubic spline function interpolation, the number of interpolated pulses and pulse frequency are input into the position control board of the servo system, and the servo motor is driven to realize x-C linkage. The machine tool adopts the x-C two axis linkage type automobile shock absorber spring fatigue life. How to do the simulation analysis formula to generate the cam contour curve? The actual contour of the cam has a significant effect on the improvement of the performance of aluminum materials. The general mathematical model of x-C linkage coordinates is determined by the parameters such as polar coordinate value, grinding wheel radius, grinding wheel dressing amount, grinding feed rate, etc. see Figure 1. The actual contour of the cam () is known, and the coordinate system x'oy'is fixed on the center of the cam. During grinding, the grinding wheel contacts the contour of the cam in the normal direction. In Figure 1, O (o') is the fixed reference point of the cam, moving back and forth along the X direction, and point B is the center of the grinding wheel. The grinding wheel radius RW after I times of dressing is:

where rw0 is the initial radius of the grinding wheel; DRW is the dressing amount of grinding wheel each time; Is the reduction of the grinding wheel in the radius direction after I times of grinding wheel dressing. Also: when considering the grinding wheel dressing and grinding feed, the distance SX from the center point of the grinding wheel B to the center point of the cam o is:

Where, it is the total grinding allowance of the cam; N is the total number of grinding turns; It is the thickness of the cam profile after grinding I circle. Substituting equation (5) into equation (2), the mathematical model of cam grinding is:

II. Under the condition of constant linear speed control, the mathematical model of linkage coordinates. When the c-axis is grinded at constant speed, due to the continuous change of the lift of the cam contour, the linear speed of each point of the cam contour also changes, resulting in uneven grinding. During the grinding process, the metal grinding rate changes with the change of the curve of the cam contour surface, Thus, according to the number of screws, the burning extruder can be divided into single screw, twin screw and multi screw extruders, and cam surface waviness. The change law of grinding cam in one cycle: the change of metal grinding rate is in the order of base circle lift peach tip circle return base circle. Both cam width B and grinding depth AP can be considered as fixed invariants, so the instantaneous linear velocity V at the cam grinding point determines the grinding rate. As long as the speed of axis C is controlled so that V is a constant value, constant grinding removal rate grinding can be achieved. Figure 2 shows three positions during grinding. Grind off the cam contour area sa1a2b2b1 in time T1 and sa2a3b3b2 in time T2. Constant grinding rate refers to the equal volume of metal ground in unit time, that is:

3.6 radioisotope method

now enlarge the local area a1a2b2b1 and approximate it to a curved parallelogram, as shown in Figure 3. One side of the parallelogram (the length of arc A1B1) is D, and its height is AP, so formula (7) is changed into:

where k is a constant, k = grinding rate/apb. Thus, the rotation law of the c-axis is controlled, and the variable speed constant grinding rate is realized to control the grinding of the cam

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