| Along with the widening of mould application and forever pursuing in aesthetics to people, more and more moulds production are produced with free surface, and the surface precision desire are more and more high. Because the high precision equipments such as high speed milling machine can't apply in china, the polishing process depend on the handwork craftsmanship of workers. In the one side, this condition makes the production periods of mould longer, in the other side which is the most important, because the mould surface precision depends on the polishing skill of workers, the precision of mould surface can not be guaranteed. This contravention is more extreme in auto moulds and auto light moulds. How to improve the machining precision and roughness of mould free surface and reduce the craft polishing quantity is an earnest resolved problem in the mould field in china. However the Magnetic Abrasive Finishing which is a high flexible machining method focused by international take a hope to solve the difficult problem.Based on the exceed extractive special machining technique of part surface and united with the characteristic of polishing mould free surface, this item brings forward an idea which compounds the ultrasonic machining technique with the magnetic abrasive finishing technique and designs a exceed extractive special machining system of ultrasonic magnetic abrasive finishing in mould free surface polishing based on the upright numerical control milling machine. This item compounding the ultrasonic machining technique with the magnetic abrasive finishing technique to polish the mould free surface is the first try in the world.According to the force model of magnetic abrasive grain in machining area, the stuff cutting model and polishing mechanism of the ultrasonic magnetic abrasive finishing in process of polishing mould free surface are summarized in this paper. The vibrating characteristic and machining trait of ultrasonic makes the magnetic grains overturn and sharp. At the same time, the ultrasonic produces impaction effect onto the grains. These situations will improve the machining efficiency of MAF. Large number of tests indicate that the additional ultrasonic makes the polishing efficiency improve more than single magnetic abrasive finishing when the grains are disabled. We also find that the polishing results are not satisfied in process of UMAF because the ultrasonic vibration impact trait and machining trait influence the rigidity of magnetic brush when the grains are sharp in process of polishing. At last we validated the feasibility of UMAF system in process of polishing mould free surface by lots of tests.Now in the process of MAF, the short life of magnetic abrasive grains and the poor polishing efficiency restrict the development and application of MAF. Aim at the condition of MAF, this item put forward a new technique which make the magnetic abrasive grains of machining area with additional vibration of ultrasonic to improve the magnetic abrasive grains self-sharp and turnover. So this compound polishing technique will enhance the using efficiency of magnetic abrasive grains.At the same time, applying the SPS technique onto magnetic abrasive grains production is a new try. The SPS technique is entering the impulse current between the metal grains or powders to sinter, so it is also named Plasma Activited Sintering-PAS or Plasma Assisted Sintering-PAS. According to the tests of this item, we find that the magnetic abrasive grain made by SPS technique has a high mechanic intension and this grains accord with the application. This new try has provided a new idea for producing the magnetic abrasive grains with high capability and mechanic intension.This paper makes theory and test analyses about UMAF as the discussing focus. The material chapters are shown as follow. The first chapter is introduction. In this chapter, the basic principle, machining trait, development situation and development trend of MAF are summarized. Then the research background and its research signification of this item are discussed. The second chapter is basic magnetic field theory analyses. At first the electromagnetism field theory and theorem are discussed, and then the magnetic calculate of multilayer solenoid model is deduced, second the magnetization mechanism of magnetism medium is analyzed, at last the force of magnetic abrasive grains in machining area is analyzed. This chapter offered the theory support to polishing mechanism of UMAF.The third chapter is the polishing mechanism of UMAF. The special machining principle of ultrasonic and its character are analyzed in this chapter. Based on the MAF, we find that it is feasibility to compound these two special mechanisms. Though the force analyses of the grains in machining area we deduced the stuff cutting model of a single magnetic abrasive grain. And then we summarized the polishing mechanism of UMAF.The fourth chapter is the spark plasma sintering of magnetic abrasive grain. The principle and sintering crafts of SPS are summarized in this chapter. Then we analyzed the sintering body based on the sintering crafts. The feasibility of sintering magnetic abrasive grain though SPS is proved by experiments in this chapter.The fifth chapter is the test analyzing of UMAF. Though the discussing and analyzing in up chapters, we designed a UMAF system by ourselves and made lots of tests on it. At the same time, we analyzed the results of tests and optimized the tests.The sixth chapter is the conclusion and expectation. |
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