MIM is an acronym formed from the term Metal Injection Molding, referring to a revolutionary and relatively little-known process. Invented just over three decades ago, this technology combines traditional powder metallurgy with plastic injection molding. Thanks to continuous development, the technology has become increasingly refined over the past decades, and as a result, it is now possible to produce extremely precise metal components using this method—significantly faster than with other techniques.
The stages of the process
MIM is essentially a metalworking process in which very fine metal powder is mixed with a binder—some type of polymer such as wax or polypropylene—while heated. This step must be done in a heated state so that the binder coats every metal particle evenly. After cooling, the resulting mixture is turned into granules for the injection-molding phase.
During injection molding, the granules are melted, turning into a toothpaste-like material capable of filling even highly complex mold shapes. The molded part produced at this stage is called the “green part.” These green parts, which are still significantly larger than the final product, undergo a special chemical process to remove most of the binder—typically around 40% by volume. This binder-removal process is called “debinding.” Debinding can be carried out using catalytic processes, thermal furnaces, solvent baths, or a combination of these.
After the binder removal, the result is the “brown part.” Following debinding comes the removal of the remaining binder—this is the sintering stage. Sintering takes place in a vacuum furnace, where the part attains its final size (usually about 20% smaller than the brown part) and density.
Advantages of MIM
The economic advantage of MIM-molded components is primarily due to the complexity of small parts and the speed at which they can be produced. With this method, it is possible to manufacture components that either cannot be made by other production techniques or could only be produced at significantly higher cost. Another major benefit is that MIM technology can be used with virtually no material loss: leftover material can be recycled into new granules. This makes the process especially cost-effective for expensive metals such as copper, titanium, or tungsten.