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Quick Facts
Metal injection molding is a relatively new process that "injection molds"
metal parts that have densities greater than 97%. A wide variety of materials
can be used to produce metal injection molded (MIM) parts, including low alloy
steel, stainless steel, titanium. MIM parts currently being produced are
relatively small in size compared to metal castings, but offer advantages over
many casting processes due to the complex geometry that can be attained using
the process. close tolerances the process is capable of providing.
The Process
Metal powders, combined with a binder, are injected into a metal tool,
similar to plastic injection molding. Once molded, removal of the binder from
the green part is necessary. Debinding of the part occurs either through
heating (causing the binder to melt, decompose, and/or evaporate) or by
dissolving the binder by use of solvents. Parts are then sintered (heating of
the part that results in the separate metal particles welding together) to
create a completed part. Completed parts normally exceed 97% density and have
mechanical properties that are similar to wrought materials. Once completed,
the parts may be further machined, painted, annealed, etc.
Metal Injection Molding Advantages
Parts made by the metal injection molding process are generally complex in
shape, thereby reducing machining. Since parts are injected molded, large
quantities can be made at relatively low cost. With the high density parts
that are produced, mechanical properties are similar to those achieved through
wrought materials.
Metal Injection Molding Disadvantages
In general, MIM parts are most competitively priced when they are produced in
higher volumes. Prototyping is expensive due to the requirement to have a metal
tool to accurately represent the finished part. Due to the adherent oxide film
that is always present, thereby inhibiting sintering, aluminum is not a material
that is metal injection molded.
Alloys
Nearly all ferrous materials may be metal injection molded, including low and
high alloy steels, stainless steels, titanium and inconel.
Tooling
Metal tools, similar to plastic injection molding tools, are used for the MIM
process.
Design and Technical
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