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Debinding and sintering of metal injection molding components

MIM has obvious advantages over traditional metal forming processes

MIM (Metal Powder Injection Molding) is a near-net forming technology that combines traditional powder metallurgy technology with modern plastic injection molding technology. The production process is to first select metal powder and binder that meet the requirements, and then heat them at a certain temperature. It is mixed into a uniform feed material, and then injection molded through a mold to form a green body. The green body is then degreased and sintered to densify the metal powder, and finally the finished product is formed.+

The core technologies involved in the production process of MIM products are as follows:

Injection molding: A process in which granular feed materials are heated to a certain temperature to make them fluid, and then injected into the mold cavity to cool down to obtain an embryo of the desired shape; the core technology is that due to the wide variety of metal powders, various feed materials Ingredients vary in content, and the setting of parameters during the injection molding process is very important. Operational errors will cause product defects. Excellent injection capabilities require company technicians to simulate the injection molding process, determine parameters, and select molds. Wait for preparations to ensure the uniformity of the injection.

Degreasing: the process of placing the formed blank into a special container to remove the binder component; process: mainly includes three major systems, wax-based system (solvent degreasing), plastic-based system (catalytic degreasing) and thermal degreasing system. The main ones in the industry The core advantage of using a plastic-based system (catalytic degreasing) is that no seasoning is required and the process is simple. The disadvantage is that the price of imported feed materials is high and the raw materials cannot be fine-tuned; core technology: the degreasing process directly affects the residue of the binder in the blank If the degreasing treatment is not in place, there will be too much binder residue. When a large amount of binder decomposes and vaporizes during high-temperature sintering, it will easily cause the product to burst; if the degreasing process is excessive, it may cause adverse consequences such as metal oxidation and structural deformation of the product. Therefore, the selection of degreasing process and the control of process parameters are particularly important.

Vacuum sintering: The degreased parts are put into a high-temperature and high-pressure controlled vacuum sintering furnace. The parts are slowly heated to remove the residual binder. After the binder is completely removed, the parts are heated at high temperature, and the particles between the particles are The voids will disappear due to the fusion of particles, and the final part will shrink to its designed size and transform into a dense solid; core technology: due to the existence of pores between particles, the blank will shrink during sintering, and different materials will shrink during the sintering process. The shrinkage rates vary, generally between 15% and 18%, so controlling the shrinkage rate by controlling sintering time, temperature and other parameters is the core.

Post-processing process: including shaping, metal processing and surface treatment (including PVD, CNC, laser engraving, sandblasting, polishing, grinding, etc.), of which the company can make its own processes including shaping, sandblasting, grinding, and CNC.

Inspection: The inspection content includes dimensional inspection, appearance inspection, deformation inspection, etc. Common defects include dents, excess materials, gaps, defective door panels, crushing, etc.; Core technology: At present, the MIM industry has not implemented batch automatic inspection. The core reason The reason is that the downstream demand iteration speed is too fast. If fully automatic detection equipment is used, the frequency of replacement or parameter adjustment is too high.

Advantages of degreasing and sintering metal injection molded parts

MIM has the advantages of unrestricted structure, high product precision, and low cost. For complex parts, traditional metal forming usually involves disassembling and producing individual parts before assembling them. The MIM process is more economical through overall processing and simplified processing procedures. Moreover, the cost of traditional metal forming increases as the complexity of the parts increases. The MIM process keeps the cost constant by increasing the complexity of the mold. The higher the complexity of the product, the more economical the MIM process is and the more obvious the cost advantage.

Specifically, the advantages include: (1) Unlimited structure: complex metal parts can be directly formed like plastic injection molding, allowing free design of three-dimensional shapes. In theory, all shapes that can be molded by plastic can be realized through the MIM process; (2) Reliable physical properties: the product has a uniform structure and good density, and the density can reach more than 98% of the theoretical density. The product has high mechanical properties such as strength, hardness, and elongation; (3) High product precision: the dimensional accuracy of the product can be achieved after one-time molding Reaching +/-0.3%, products with general accuracy requirements do not require post-processing; (4) The batch cost advantage is significant: the near-net shape process, compared with other processes, especially products with complex structures, uses the MIM process to mass produce obvious cost advantages.