Metal powders require vacuum sintering, while plastics do not. There are also differences in the injection process, such as temperature and pressure. Metal powder injection molding (MIM for short) technology is a new near-net-shape molding technology used in the metal injection molding factory. It is the product of the interpenetration and intersection of multiple disciplines such as plastic injection molding technology, polymer chemistry, powder metallurgy technology and metal materials science. Structural parts with complex three-dimensional shapes, especially some small parts with complex shapes that are processed by machining methods or difficult to process, MIM technology can be easily completed, and has the advantages of low cost, high efficiency, good consistency, etc. It is easy to form mass production. The points to be noted in the powder injection molding process are as follows.
Metal powder injection molding process: the sintering density of pf-3f, phenolic-5f, pf-10f and pf-15f four metal powders at different sintering temperatures. It can be seen that within a certain temperature range, the higher the sintering temperature, the greater the sintering density, and the smaller the change. With the sintering temperature, within a certain range, the larger the size of the powder, the greater the sintered density. Spherical powder is beneficial to improve the density of vibration, improve the bearing capacity and improve the sintered density.
Note on powder injection molding mim process flow: The viscosity increases with the increase of solid content. When the solid content reaches 62%, after injection, the viscosity increases sharply, making the solid content limit (MAX62%). When the binder is not enough, there is a gap between the two, which will affect the powder product. The mechanical strength of the binder is too much, and the solid content is too low, which will affect the degreasing and sintering shrinkage.
The door should be in a higher position in space, thereby reducing the friction feeding of the melt in the mold, reducing the injection pressure, and reducing the possibility of deformation of the product. In addition, the design of the flash point is also very important, and the flash point is used for loading during the cold powder injection molding process to ensure the consistency of the product.
Metal powder injection molding technology products not only have the characteristics of "plastic injection molding" process with complex shapes and easy mass production, but also have physical, chemical and mechanical properties close to precision casting and forging, and have three-dimensional complex geometric shapes in the preparation, homogeneous structure and high-performance near-net-shaped products have unique advantages.
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