Study On Selective Laser Sintering Of Metal And Polymer Powder Composite And Post Process

Selective laser sintering(SLS) is a kind of mature rapid prototyping(RP). At present it is hot issue and difficult problem that SLS is applied to manufacture metal part and mould rapidly. The rapid manufacture of metal part and mould has wide application in mechanical industry. A coated metal powder has been used to fabricate metal part and applied to mould industry successfully through indirect SLS in the foreign country. But the technology and material are kept secret to our country. The purpose of this paper is focus on indirect selective laser sintering metal and polymer powder composite parts and its post processing technology. The main research contents and results are as follows:Epoxy resin and metal powder are averagely mixed as SLS material which is very easy to produce with low cost and good forming property. Two kinds of Epoxy resin, E-20 and E-12 are investigated as binder according to combination with single metal powder as metal of 316L, electrolytic iron powder and composite metal powder(Fe-Cu-C, Fe-Cu-Ni and Fe-Cu-Ni-C)are selected as structure material. The proportion of the binder is also determined.The mechanism of laser sintering for SLS material has been discussed. The effect of sintering parameters on strength and accuracy of green part is analysed theoretically. Sintering parameters which include laser power, scanning speed, scanning space and layer thickness are optimized as follows: P=14w, v=2000mm/s, d=0.1mm, h=0.1mm.Post-processing of green part has been investigated too. A series of method is summarized for removing powder to erose parts. Debinding temperature, keeping time and protection atmosphere are analysed for removal of binder. High temperature sintering study focus on mechanism and process of sintering, effect of sintering parameter on property of sinter, sum of shrinkage during sintering. The ways to reducing and compensation of shrinkage are also discussed.For the sake of improving their mechanical properties, the modified epoxy resin is used to infiltrate and densify the parts. The mechanical properties of infiltrated and uninfiltrated parts are investigated respectively. At the same time, the infiltrating temperature, curing temperature, curing time and heat resistant temperature of the resin are researched through differential scan calorimetry(DSC), thermal gravity analysis(TGA) and scanning electron microscopy(SEM) respectively. The results show that mechanical properties of the infiltrated parts are enhanced greatly, almost 4 times. Moreover, the density of the parts is greatly improved, and the heat resistant temperature can up to 200℃. Therefore, based on study of indireect selective laser sintering metal and polymer powder composite parts, the plastic injection mold can be manufactured through this method successfully, which can satisfy for low requestment user to metal parts and moulds.