Investigations On Magnetic Abrasive Finishing For The Mold Surface

In the process of manufacturing mold,polishing on mold surface directly affects the quality and life-span of product.Because of complexity and variety of mold surface,most of finishing for mold surface still must be done by hand work.Therefore,it greatly restricts the development of mold industry.Magnetic abrasive finishing(MAF)has great effect at the complex mold surface finishing due to its flexibility and self-adaptability.Based on the analyses of magnetic force and grinding mechanism of MAF, investigations on the relative techniques of MAF for mold surface were performed with theory analyses and experiments.Based on the theory of static magnetic field,the simulation model of electromagnetic inductor(EI)was constructed by finite element analysis software Maxwell.Simulation analyses about the effects of diameter parameter of the core,magnetic pole form,protruding magnetic pole, distribution of magnetic field,electric current,working clearance on magnetic field were performed.Then,the results of simulation analyses were approved by experiments.That provides with a theoretical groundwork for magnetic abrasive finishing experiment and structure design of EI.Then, based on the results of simulation analyses,the MAF machine tool was developed.Experiments of MAF for plane workpiece were performed by orthogonal experiment method with mixed weight of unbonded magnetic abrasives.The influences of abrasive consistency,magnetic flux density,working clearance,rotational speed of magnetic pole,feed speed and finishing time on surface roughness were investigated.Then,the best levels of factors and the effect law on MAF of factors were obtained.Experimental results indicate that unbonded magnetic abrasives aren't suitable for the MAF whose tool rotates,due to the centrifugal force. Experiments and theory analyses of MAF were performed with bonded magnetic abrasives.The effects of the magnetic flux density,working clearance,rotational speed of magnetic pole and finishing time on surface roughness were investigated by finishing plane workpiece.Better surface roughness can be obtained,when magnetic flux density B=1.2～1.4T, working clearance is about 1.2mm,rotational speed of magnetic pole n=2500r/min,finishing time is 4min.Then,the experiments of finishing the representative concaves and convexities with MAF were performed,and the investigations about the different effects of the magnetic flux density, working clearance,rotational speed of magnetic pole and finishing times on surface roughness were done.The results indicate that better surface roughness can be obtained,when magnetic flux density B=1.3&1.2T, working clearance is 1.0～1.5mm,rotational speed of magnetic pole n=2500r/min,finishing times is 6～8.Based on the MAF experiments of concave mold and convex mold, aiming at the problem of non-uniform material removal on the mold surface in MAF,the main effect factors are analyzed.Then,the corresponding ways for solution were presented by proving the shape of magnetic pole and polishing trajectory etc.The results offer a theoretical foundation for the development and application of MAF technology in mold industry.