| 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 injection moulds rapidly and directly. The rapid manufacture of injection mould which can be used in trial-produce and short run of common plastic has wide application in mechanical industry. A coated metal powder has been used to fabricate injection moulds applied to mould industry successfully through indirect SLS in the foreign country. But the technology and materials are kept secret to us. In order to fill in the gaps of our country in materials and technology of rapid tooling, the paper was focus on selective laser sintering copper polyamide composite to fabricate moulds directly and its post processing technology. The main research contents and results are as follows:Copper polyamide composite mixed mechanically and copper coated by polyamide are investigated as SLS materials. mass ratio of polyamide and copper was determined according to the request performance of injection moulds. The mechanism of laser sintering for SLS material has been discussed through the analysis of interfacial action of copper and polyamide.The effect of sintering parameters which includes bed temperature, laser power, scanning speed and layer thickness on strength and accuracy of green part is analysed experimentally. And the forming technics was optimized and a more dense structure can be built at Tbed = 165℃, P=15W, v=2000mm/s, d=0.15mm. The tensile strength and flexural strength of test sample after infiltration on epoxy can reach 34.76MPa and 51.75MPa. Prototype quantities (100 to 400 parts) of common plastic can be manufactured with these mould inserts.Polyamide coated copper composite has good forming property and can achieve good precision. Orthogonal test design was adopt to research the effect and interactive of themselves of sintering parameters on flexural strength of samples. And each parameter choose three level correction. The best forming condition is Tbed = 165℃, P=20W, v=1500mm/s, d=0.08mm, under which we can get the flexural strength of 97MPa and hardness of 77(HRM) after infiltration. The mechanical properties was better than those of DTM composition (Flexural strength could reach 58.3MPa and hardness 75/Shore)Post processing of green part has been investigated too. A series of method is summarized for removing loosing powder from formed parts. The copper polyamide parts as built in the sinterstation are porous. The inserts must be sealed to prevent the molded plastic from adhering to the surface and to prevent the conformal cooling lines from leaking. A low viscosity epoxy works well to seal the surface. In addition, the infiltration can improve the mechanical properties of inserts greatly. The improvement of different infiltration system on sample flexural strength was researched. At the same time, the infiltration temperature, curing temperature, curing time and heat resistant temperature of the resin are studied through Differential Scanning Calorimetry (DSC) and Thermal Gravity Analysis (TGA). The results show that mechanical properties of the infiltrated parts are improved greatly, the resin-solidification system of CYD-128/MNA/DMP-30 especially, almost 3 times enhanced. Moreover, the density of the parts is greatly improved, and the heat resistant temperature can up to 250℃. A good surface roughness and hardness can be got from finishing with a flexible sanding cloth.Therefore, based on study of selective laser sintering copper polyamide composite parts, the plastic injection mold can be manufactured through this method successfully, which can satisfy for trial-production and short run of common plastics. Besides that, it gets low cost and can mould injection molds with conformal cooling channel directly which can improve the efficiency of injecting obviously.
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