The MIM process
Metal injection molding (MIM) merges two established technologies, plastic injection molding and powdered metallurgy. This frees designers from the traditional constraints associated with trying to shape stainless steel, nickel iron, copper, titanium and other metals. The result? Greater design freedom and more opportunity for innovation.
Before we begin, our engineers will work closely with you to determine if the component is economically and physically suited for MIM. Where appropriate, we will recommend design changes so you achieve the maximum benefit from our process.
Step 1: Feedstock
Very fine metal powders are combined with thermoplastic and wax binders in a precise recipe. A proprietary compounding process creates a homogenous pelletized feedstock that can be injection molded just like plastic. This achieves ultra-high density and close tolerances over high-production runs.
- Unlike standard powder metallurgy, which can achieve only 80-90% of theoretical density, MIM results in 95-100%. This means we can achieve close tolerances and reduce costs by producing small, complex parts over high production runs.
Step 2: Molding
- The feedstock is heated and injected into a mold cavity under high pressure. This enables us to produce extremely complex shapes and allows for shorter cycle times.
- Once molded, the component is referred to as a “green” part. Its geometry is identical to the finished piece but is about 20% larger to allow for shrinkage during the final sintering phase.
Step 3: Debinding
- Binder removal (debinding) involves a controlled process to remove most of the binders and prepare the part for the final step – sintering.
- Once debinding is complete, the component is referred to as “brown.”
Step 4: Sintering
- The brown part is held together by a small amount of the binder, and is very fragile.
- Sintering eliminates the remaining binder and gives the part its final geometry and strength.
- During sintering, the part is subjected to temperatures near the melting point of the material.