Main Steps of the Metal Injection Molding Process
1. Compounding
The MIM process begins with feedstock preparation, where fine metal powder is blended with thermoplastic and wax binders. The blend is heated, causing the binders to melt. The material is mechanically mixed until all the metal powder particles are uniformly distributed within the binder. The mass is then cooled and granulated into feedstock that can be used in the MIM machine.
2. Injection Molding
If you’re familiar with plastic injection molding, you’ll have a good grasp of how MIM works. First, the feedstock is placed into the MIM machine, where it’s heated and injected into a mold cavity under high pressure. The ‘green’ part is then allowed to cool and removed from the mold so the process can be repeated.
3. Debinding
The part is now ready to move onto the debinding, or binder removal process. The majority of debinding takes place prior to sintering, leaving behind just enough binder to handle the parts into the furnace. After debinding, the part will be semi-porous, which allows the remaining binder to escape during the sintering process.
4. Sintering
During the sintering process, the brown parts are loaded into a high temperature, atmosphere controlled sintering furnace, where they are slowly heated to evaporate the remainder of the binders. Once all of the binders have been released, the component is heated, where it shrinks, transforming into a dense solid.
