| Manufacturing capacity of high-end CNC machine tools largely reflects anational science and technology level and comprehensive strength. Our country haslisted it as one of16major projects in the National Medium and Long-term Scienceand Technology Development Plan (2006-2020). How to improve the accuracy andefficiency of the high-end CNC grinding grinder is a hot topic of research in thegrinding field of high-end CNC grinding machine. The paper is no other than to solvethe problem of the accuracy and efficiency of high-end CNC non-circular grindingmachine in the grinding process, the key control technologies with high-accuracy andhigh-efficiency of automobile have been deeply studied with the support of nationalscience and technology support program. The main contents include:(1) According to the grinding accuracy and efficiency of high-end CNCnon-circular grinding machine, the ideal kinematics mathematical model ofnon-circular grinding wheel feeding and work-piece rotation two axes linkage isestablished which is based on the tracing grinding method of the tangential points, theprinciple of the constant grinding rate, the shape of the cam and the relationshipbetween the spatial position of the wheel. The constraints of grinding wheel feedingand work-piece rotation are determined which is on the basis of the requirements ofthe transmission mechanism characteristics of the system, the driving ability of thesystem, the grinding accuracy of the cam and others, the difficult machining pr oblemin the non-circular grinding process is solved.(2) According to the low grinding efficiency of the cam, a new method fortwo-way searching adaptive synchronous accelerated control of grinding wheelfeeding is presented, which the chord error, the grinding wheel speed, accelerationand jerk are limited. The high efficient processing problem of the non-circulargrinding is solved on the premise of guaranteeing machining accuracy. Thecorrectness and effectiveness of the method are verified through the relevantexperiment, the results show that the efficiency is increased by16.78%than theoriginal machine.(3) According to the local lift error tolerance in the grinding process of the cam,a new method for discrete points fitting of cam lift error of adaptive weighted supportvector machine (WSVM) is put forward. The problem of the cam lift errorcompensation is solved, which the smoothness between error points. The relationshipbetween the angle and the weighted value are determined by the symbols of t he roundrate, the accuracy of non-circular grinding is implemented.(4) According to on-line detection and dressing of the state of grinding wheel wear, a method for on-line detection and dressing of grinding wheel state in theprocess of grinding is raised, which the acoustic emission signals are taken as theresearch object. The method based on wavelet and FFT is used to get the differentfeature vectors of work-piece with grinding wheel machining and grinding wheel withdiamond roller dressing. The RBF neural network based on the feature vectors of thework-piece with grinding wheel machining and the grinding wheel with diamondroller dressing is established, and the problem of on-line detection and dressing of thestate of grinding wheel wear is solved. It is verified that the method can accuratelydifferentiate the sharp moments of the grinding wheel dressing and the dullness timeof work-piece with grinding machining. The error rate of the sharp moments of thegrinding wheel dressing is less than10-4.(5) According to the need of the high-accuracy and high-efficiency machiningequipment of camshaft, a high-accuracy and high-efficiency schematic diagram of thecontrol system of camshaft grinding machine is put forward. The module of lineardriver of grinding wheel feeding, the module of work-piece rotation and the module ofCBN high-speed hybrid motor spindle are developed. The control system ofnon-circular, the machining program of CNC and the control program of PLC areexploited. The results show that the grinding accuracy of the machine tools isascended from±0.025mm to within±0.015mm，the tests have exhibited that thesurface roughness Ra is raised from the original0.32m to within0.25m。And itsmachining efficiency is increased from280seconds to233seconds (four-cylinder andeight-piece camshaft).The method for two-way searching adaptive synchronous acceleration control ofgrinding wheel feeding, the method for discrete points fitting of cam lift error ofadaptive weighted support vector machine (WSVM) and the method of on-linedetection and prediction of the state of grinding wheel wear presented in this paperare provided the theoretical basis and the technical support of high-accuracy andhigh-efficiency non-circular grinding intelligent control system, which is valuable forthe development of other CNC non-circular grinding equipment. At the present, theperformance indexes of the developed serial CNC camshaft grinding machines basedon the research are reached the expected the design goal, which the machine toolshave been applied to the market. The whole process of CNC camshaft grindingmachine which is from the product research and development, the achievements to theindustrialization has been completed. |
PDF Full Text Request