The Research On The Influencing Factors And The Key Technology For The Machining Quality Of High Speed Camshaft Grinding

As a key component,the camshaft is widely used in car and engine industries,whose accuracy and stability of quality directly affect the engine quality,life,emissions and energy saving.With the outbreak of the energy crisis and the implementation of the new standards,how to improve the machining efficiency and machining quality of the camshaft is becoming the urgent problem to be solved.To ensure the machining quality and machining efficiency of the camshaft,a high performance camshaft grinding machine is generally used in the process of high efficiency and precision grinding.But the camshaft is a slender shaft,its rigidity is poor,and its contour line is complex,which bring great difficulty to the grinding process.The article aims to analyze the influencing factors and study the key technologies for the machining quality of camsh aft grinding based on the high speed camshaft NC grinding.The key technologies breakthrough to improve grinding quality is made in the original lift data fitting and optimization,the multi pass grinding to reduce the elastic yield,the grinding stability analysis and chatter suppression,the workpiece speed optimization as well as grinding error analysis and compensation,which can solve the problems that the measurement error of original lift data,the feed elastic yield of grinding wheel frame,grinding vibration,and the grinding contour error are greater during the camshaft grinding.The main contents of the research are as follows:1)The camshaft grinding method and its processing characteristics are analyzed.The discrete data of cam lift that contains measurement error is smoothed by the cubic spline interpolation method,which can achieve the optimal fitting for the original lift of camshaft.The gringding process of camshaft X-C axies linkage NC grinding is introduced based on the mathematical model of approximate constant linear velocity for camshaft grinding.2)A mathematical model of normal grinding force of camshaft grinding i s established.The experimental study of grinding force and grinding wheel yield displacement are carried out.The elastic yielding regularity under different angle,grinding depth and grinding pass is discussed.Through multi pass grinding,the elastic yielding of the grinding wheel can be reduced.The resonance frequency and critical speed for some main components of camshaft grinding machine are analyzed by the dynamic stiffness testing,and the weak stiffness in the machining process are found.The optimization measures are given for the weak links.3)A dynamic model of the high speed camshaft grinding process is established,and the stability and instability region of camshaft grinding are analyzed.By modal analysis,the natural models and natural freq uencies of the grinding process system are solved,and the weak links are obtained.Combined with the stability lobe diagram,the weak link of the system and the control theory,the related vibration suppression methods are proposed.4)The Simulink simulation model of the cam shaft grinding system is established,and the critical stable grinding depth of the high speed camshaft grinding is obtained.The vibration suppression effect of variable speed grinding is verified by simulation.The influence of grinding parameters on the processing waviness and roughness is studied experimentally,and the correctness of the stability lobe chart is verified.The optimal speed ratio and the best grinding wheel speed range for the camshaft high speed grinding is presente d.5)It is found that there are some rotation angle intervals of camshaft,where the feeding speed,acceleration and jerk of grinding wheel frame are beyond the maximum value allowed by grinding servo system in the camshaft X-C axis linkage grinding with constant linear velocity.Based on the calculation model for different acceleration of the grinding wheel frame,the workpiece spindle speed is calculated by integral reverse seeking method,and the workpiece spindle speed of the above intervals is replaced,then the whole workpiece spindle speed is fitted by the cubic spline curve.Through the comparison experiments of the workpiece spindle speed optimization before and after,the correctness of the optimization method of the workpiece spindle speed is verified.6)The change trends of the cam lift error and the cam contour error are analyzed.The virtual cam lift model and its least square fitting algorithm are established.Then,the lift error analysis and compensation model is established for the camshaft X-C axis linkage grinding.The camshaft grinding experiment is conducted using virtual lift after error compensation process to verify the correctness of the model.