Metal Injection Molding (MIM) is a molding technology that achieves near net-shape metal parts. The process involves combining ultra-fine metal powders and a polymer binder system to create a feedstock suitable for injection molding. The polymer binders are later removed and the remaining metal powders are sintered to achieve final part geometries and material chemistry. MIM is best for parts with complex geometries, low part mass, and medium to high production volumes. Because it is a molding process, MIM offers value in design flexibility that is often too expensive to achieve by machining.
Metal Injection Molding Process
What is MIM?
The MIM process has been highly engineered over several decades, with top-notch equipment manufacturers, researchers, and engineers creating significant advancements along the way. The process starts with the combination of metal powders and a polymer binder, creating a feedstock for injection molding. Once introduced to the molding machine, the feedstock becomes viscous as the polymer binder is heated in the barrel of the molding machine. The feedstock is then injected into molds similar to how plastic parts are formed, creating a “green” part. Since the binder system is only required for the molding process, it must be removed from the part. This can be done thermally or by solvent extraction. After debinding has been completed, the parts are sintered at very high temperatures in vacuum or continuous furnaces. During the sintering process, the high surface energy of the fine metal powders is released and the powders consolidate to form a solid metal part approaching 96-98% of full density. A broad range of secondary operations can be applied to achieve a variety of final part specifications.
A broad range of materials are available from the MIM process. Categories include:
- Low alloy steels
- Stainless steels
- Tool steels
- Soft magnetic alloys
- Super alloys
To read more about specific material chemistries, download our material properties sheet.
You can find MIM applications in almost every major market category, including aerospace, automotive, commercial, dental, electronics, firearms, industrial, and sporting goods. Any potential MIM application should consider the process’ inherent design flexibility. This means sophisticated geometries, multiple part combinations, assembly streamlining, mass reduction, and custom physical properties can be considered.
When choosing a manufacturing process, you are seeking the greatest value for your part. MIM performs best with small, high complexity metal parts that would normally require five or more process steps to be produced by machining.
The Liquidmetal team is here to help you gain the most value, and that begins with assessing your application, and geometry requirements. Not all applications are perfect for MIM (or Amorphous Metals), but the Liquidmetal experts are trained to find those that are. If we can’t help solve your problem with MIM or Amorphous Metals, we will help point you in the right direction.
What characteristics generally describe good MIM applications?
Lengths less than 75mm
Wall thickness from 1-3mm
Weight under 25 grams
Volumes from 100,000-100,000,000 annually
Lengths up to 150mm
Wall thickness to 13mm
Weight of 50-150 grams
Volumes under 100,000 annually