Metal powder injection molding technology is a very economic method to produce a variety of components. It is an excellent alternative to other forms of metal processing. Usually, the volume of parts produced by metal powder injection molding is small. So what is the process of producing parts by metal powder injection molding?
1. Mixture and granulation of metal powder injection molding
The mixture is to evenly mix the metal powder and organic binder to make various raw materials into the mixture for metal powder injection molding. Granulation is to extrude the mixture into granules. The particle size of metal powder used in metal injection molding process is generally 0.5 ~ 20 μm. In theory, the smaller particle is, the larger the specific surface area is, and the easier it is to form and sinter. The function of organic binder is to bond metal powder particles, so that the mixture has rheology and lubricity after heating in the injection molding machine, that is, the binder is the carrier to drive the powder flow. Therefore, the choice of binder is the key to the whole metal powder injection molding. The common binders are PP, PE, EVA, PEG and POM.
2. Injection of metal powder injection molding
Using the injection machine to heat the MIM feeding and evenly fill it into the mold cavity. The MIM injection blank is obtained after cooling. Mold conforming to the characteristics of metal powder injection molding and reasonable process matching are the key of this working procedure.
3. Degreasing of metal powder injection molding
The organic binder contained in the blank must be removed before sintering. This process is called extraction. The extraction process of metal powder injection molding must ensure that the binder is gradually discharged from different parts of the blank along the micro channel between the particles without reducing the strength of the blank. The removal rate of binder generally follows the diffusion equation.
4. Sintering of metal powder injection molding
Sintering can make porous degreasing blank shrink and densify into products with certain structure and properties. Although the properties of products are related to many process factors before sintering, in many cases, the sintering process has a great or even decisive impact on the microstructure and properties of the final products.
For parts with precise size requirements, we need to carry out necessary post-treatment. This process is the same as the heat treatment process of conventional metal products. More processes used for secondary treatment are precision CNC.