Introduction of metal powder injection molding -MIM process-1

       

Metal injection molding (MIM) is a molding method in which a plasticized mixture of metal powder and its binder is injected into a mold. Modern plastic injection molding technology is introduced into the field of powder metallurgy to form a brand-new near-net forming processing technology for metal parts. It is a high-tech that has developed rapidly in the field of powder metallurgy in recent years. The process steps of MIM are: first select the metal powder that meets the requirements of MIM and the organic binder under a certain temperature condition and mix them into a uniform feed by an appropriate method, and then use an injection molding machine under heating and plasticizing after granulation. It is injected into the mold cavity to obtain the formed blank, and then subjected to chemical or solvent extraction method degreasing treatment, and finally sintered and densified to obtain the final product.

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        Features of MIM products
  

Complexity

Like injection molding, MIM has no restrictions on shape design. Since MIM is a forming process, additional product features will not increase costs, which makes MIM an ideal way to combine individual parts into multifunctional products. MIM design rules are very similar to injection molding, so it is applicable to almost all products.

Precision

The reference design for MIM net shape accuracy is usually ±0.5% of the size. Certain characteristics can achieve a net shape of ±0.3%. Like other technologies, the higher the accuracy requirements, the higher the cost. Therefore, it is encouraged to relax the tolerance requirements appropriately when the quality permits. Tolerances that cannot be achieved by MIM one-time forming can be achieved by surface treatment.

Weight and dimensions

MIM is particularly suitable for parts weighing less than 100 grams, and less than 50 grams is the most economical. However, parts weighing up to 250 grams can also be handled. The main cost of MIM process is raw materials, so MIM uses new technology to reduce the weight of parts as much as possible. Like plastic products, the weight of parts can be reduced through the inner core and bracket without affecting the integrity of the product. MIM has outstanding performance in extremely small and micro parts, and weights less than 0.1 grams are also feasible. Weight is not a limiting factor, and products longer than 250mm can also be processed.

Thinning

Wall thicknesses less than 6 mm are most suitable for MIM. Thicker outer walls are also possible, but the cost will increase due to the long processing time and the addition of additional materials. In addition, extremely thin walls less than 0.5mm can also be achieved for MIM, but have high requirements for design.

Yield

MIM is a more flexible process, and the annual demand of several thousand to several million can be realized very economically. Like castings and injection molded parts, MIM requires customers to invest in molds and tooling costs, so for small batch products, it usually affects cost estimates.

raw material

MIM can process many materials, including iron alloys, super alloys, titanium alloys, copper alloys, refractory metals, cemented carbides, ceramics and metal matrix composites. Although non-ferrous alloys of aluminum and copper are technically feasible, they are usually processed by other, more economical methods, such as die casting or machining.