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SECONDARY OPERATIONS WITH MIM

Since the tolerance average for the MIM process falls within ±0.3%, many parts are sintered to final dimensions; however, if tighter tolerances are required for a certain feature, a secondary operation can be performed. MIM materials can be machined, tapped, drilled, broached, sized, ground, or welded like their wrought counterparts. MIM components can also be hot isostatically pressed and heat treated to improve strength, hardness, and wear resistance. And because MIM typically limits a part’s interconnected porosity to less than 0.2%, standard coloring and plating techniques can be applied without the need for special surface preparation.

It is especially important to discuss material specifications with your component fabricator because the need for secondary operations does increase component cost. Selecting the right material for your component can reduce the need for or number of secondary operations.

MIM allows for a number of secondary operations, including the following:

 



Coining or Cold Deformation

A sintered part is forced to conform to a rigid mandrel or substrate and in doing so the body is slightly deformed to match the substrate. This provides additional control for dimensional tolerances. Coining is also used to improve flatness.

Machining

All common machining operations can be applied to MIM components. Machining is often performed to add threads, undercuts, grooves, or other special features that would be difficult or expensive to accommodate in the tooling.

Heat Treatment

MIM components utilize the same heat treatment operations as their wrought counterparts to increase material properties, such as quench and tempering. In some cases, heat treatment is included within the cooling cycle or by use of a properly designed post-sintering cycle.

Hot Isostatic Pressing

Hot isostatic pressing is a process that utilizes elevated temperature and isostatic gas pressure to eliminate non-surface-connected porosity and increase density in metals. In most cases this increases the part to 100% of theoretical density and imparts the associated improved mechanical improvements accordingly. This improves the material’s mechanical properties and, potentially, workability.

Surface Carburization

Carbon is important to attaining high strengths in steels. A high surface hardness is attained with carbon surface additions using a heating cycle with an atmosphere containing a high carbon potential.

Joining

Like other metallic components, MIM components are joined by welding, brazing, or even adhesive techniques.

Surface Treatments

Surface treatments such as polishing, coating, painting, cleaning, anodizing, plating, sealing, and laser glazing can all be applied to MIM components.



 

Learn more about designing with metal injection molding from Metal Injection Molding: A Comprehensive MIM Design Guide by Randall M. German, FAPMI.

 

Find a Supplier or Fabricator

 

Whether you’re looking for a powder or feedstock supplier, an equipment provider or a fabricator of MIM components, our member directory has you covered. Explore our searchable directory of Metal Injection Molding Association Members to find the right company to fit your needs.
 

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