The Research On Some Key Technology In The Tangential Point Tracing Grinding Methods

The camshafts and crankshafts are the key components for automobile engines and other internal-combustion engines, they are in great demand,varions in kinds and strict demands for precision. Their machining quality determines the quality of engines, which directly influences the quality of car products;their machining efficiency determines the competitive power of automobile industry. To ensure the high efficiency, high contour precision and high flexibility in the machining of camshafts and crankshafts, a new method, known by the denomination "Tangential point tracing grinding", was brought forward. This thesis systemically studied the key technologies involved in design of crankshaft grinder and camshaft grinder according to the principle of tangential point tracing grinding.The motion model of tangential point tracing grinding of Non-round parts should was given respectively according to type of the parts . For crank, two motion model are given. The first is based on the principle of grinding point's uniform motion on crank, and a new idea that changes tangential point tracing grinding of crank into the state of common external grinding is described through coordinate converting. From the point of view of the kinematics, the influence of machining error caused by the tangential point tracing is analyzed. The influence and change rules of equivalent grinding thickness and grinding force of the tangential point tracing motion are discussed. The revised motion model are given. The second is based on dynamic characteristic of grinding wheel mounting, this motion model can effectively reduces the machining error caused by the tracing lag of grinding wheel mounting. Based on the principle of grinding point's constant speed motion, the motion model of tangential point tracing grinding of camshaft was given. Because the acceleration of grinding wheel mounting cann't exceed the aceleration rating of the servo motor, to increase the efficiency of grinding , the revising algorithm of grinding points uniform motion in respective sections are put forward .Grinding principium of tangential point tracing grinding, structure design and control system design of crankshaft grinder, and other involved key technologies are discussed. The factors that influences machining pricision of crankshaft grinder and the means to increase the machining precision are analyzed. By means of digital simulation, the primary factors, which influences the roundness error and size error of crankshaft in the grinding of crank using tangential point tracing grinding, are discussed. The magnitude and change rules of machining error and the influence to the shape of roundness error are analyzed. The error compensation model are put forward.To carry out the tangential point tracing grinding of crankshaft and camshaft , a specific CAM system is developed . The frame structure of the CAM system and basic function of every modules are discussed. The pattern and flow chart of information transmission in modules are analyzed. The relation between the CAM system and the CNC system was defined . The solution of the tangential point tracing grinding method became clear and full.Based on study to relation of servo system and mechanism , the inverse dynamic model of grinding wheel mounting are established . A inverse dynamic simulation software of grinding wheel mounting are developed on foundation of MATLAB/ Simulink / SimMechanics. Through two example of grinding crank, the rule of driving moment of servo motor vary along with motion law of grinding wheel mounting are analyzed . The influence of grinding force, friction force, rotate speed of stockhead , mass of grinding wheel mounting and screw-pitch on driving moment and velocity was discussed, the inverse dynamic simulation software of grinding wheel mounting are verified through compareing to the simulation results from multi-body dynamic software.Based on study to design criterion line of grinding wheel mounting, the dynamic model of grinding wheel mounting are established . A dynamic optimization design software of grinding wheel mounting are developed on foundation of ANSYS. As an example , the structural static analysis, modal analysis, harmonic response analysis , dynamic optimization design on grinding wheel mounting are implemented , the sensitivities of the objective function or state variables are studied. According to result of analysis , a new structure of grinding wheel mounting are put forward , it makes the response displacement of grinding wheel center reduced one magnitude.A series gringing experiments are proceeded to verify the Grinding principium and motion model of tangential point tracing grinding, to study the influence on roundness of crank caused by the tracing lag of grinding wheel mounting and error of grinding wheel center and stockhead center. The stressness of crankshaft are measured and error compensation model are given.