Grinding of Sintered Nd-Fe-B Magnet and Study on Computer Simulation Technology

　　Grinding of Sintered Nd-Fe-B Magnet and Study on Computer Simulation Technology
　　Sintered Nd-Fe-B is a new kind of rare earth permanent magnets, and it is the third generation permanent magnetic material following foundry magnet and ferrite magnet. Sintered Nd-Fe-B needs to be machined after sintering. It is a kind of typical difficult-to-machine material because of its high brittleness, small plastic deformation, high rigidity and low thermal stability. Ball Neodymium Magnets Grinding is an effective machining method for this material, and it is also the main method for achieving the good surface roughness. Grinding force and temperature may be reduced when admitting ultrasonic vibration in the grinding process, and loading of grinding wheel rarely takes place, the material removal rate (MRR) could be increased simultaneously. The ordinary grinding and ultrasonic vibration aided grinding of sintered Nd-Fe-B magnet were studied in the thesis. The research contents are as follows:The controlled-force radial ultrasonic vibration aided face grinding of sintered Nd-Fe-B magnet was investigated. The grinding force and speed in the process of the grinding were analyzed. The grinding force is the composition of forces which were the one produced in radial vibration assisted grinding and the one put on in the controlled-force grinding, while the grinding speed is from ultrasonic vibration speed and wheel circular velocity. The theoretical model of grinding force in the controlled-force radial ultrasonic vibration aided face grinding was put forward. The effect of grinding parameters and ultrasonic vibration on the MRR was studied. The MRR increased with the increase of the normal grinding force, and when the grinding speed was increased, the MRR increased correspondingly. On the other hand, the MRR increase when admitting ultrasonic vibration or grinding fluid in the grinding process.The grinding temperature model of sintered Nd-Fe-B magnet in the controlled-force radial ultrasonic vibration aided face grinding was founded. The theoretical calculation accorded well with experimental results.
　　The temperature in the controlled-force radial ultrasonic vibration aided face grinding is higher than that in the controlled-force face grinding. The reasons are the increase of grinding force, the increase of workpiece feed or the depth of cut. The prediction of grinding burn could be implemented making use of the relation between the normal grinding force and the tangential force. The ratio of them usually retained stated, but when grinding burn happened, the ratio changed. http://www.chinamagnets.biz    It can be judged whether grinding burn happened using this grinding temperature or power which could be gained through calculation or experiment.The effect of grinding parameters and ultrasonic vibration on the surface roughness were analyzed on the basis of experimental results. Surface roughness increase with the reducing of grinding wheel velocity, and the increase of workpiece feed speed or the depth of cut could also cause the worse surface roughness. The surface roughness produced by ultrasonic vibration aided grinding is worse than that of ordinary grinding. The prediction model of the surface roughness was founded by utilizing experimental data and back-propagation artifical neural network.The computer simulation system of ordinary grinding and ultrasonic vibration aided grinding was developed by adopting Visual Basic language cooperating with MATLAB language. This simulation system could optimize grinding parameters and predict grinding quality. Comprising the calculation of grinding force and the MRR, the simulation calculation of grinding temperature and the prediction of the surface quality were included. The entities machining simulation of partial ordinary grinding and ultrasonic vibration aided grinding were accomplished at the same time. Simulation results indicated that the optimized parameters and outcome prediction were in the error-tolerant range.