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Metal
Injection Molding (MIM) is here to stay.
Commercially available for only about 20 years, metal injection molding
is growing increasingly popular with a gamut of industries—particularly
medical device, telecommunications, electronics and automotive parts manufacturers—becoming
a viable and cost-effective alternative to other types of metal processes,
such as machining and casting. The driving force behind MIM's rise
in popularity is that the process is well suited for the high-volume manufacture
of relatively small, complex components requiring high strength, high performance
and cost efficiency.
MIM Technology Fits the Mold for Customer Needs
Metal injection molding combines the shape making capabilities of plastic
injection molding with the material flexibility of powder metallurgy. The
basic process uses pressure and heat to form precision metal parts and shapes.
Using fine metal powders in combination with a thermoplastic binder, the
mixture is heated and injected into a mold. When ejected from the mold, the
resulting "green part" is typically 15-to-25% larger than the
finished product. It is then exposed to heat, solvents or a combination thereof
to remove the binder material, leaving a part comprised of microscopic latticework
metal. This part is finally passed through a sintering furnace, which fuses
and shrinks the metal, creating a high-density, complex and precisely shaped
part that exhibits properties approaching that of wrought material. Alloys
and stainless steels, along with other non-ferrous alloys such as titanium,
are common materials used in MIM.
Advantages Over Conventional Metal-Forming Processes
MIM is attractive because it produces consistent, complex-geometry components
for high-volume, high-strength and high-performance applications. Automation
coupled with microprocessor controls allow for the production of custom-engineered
parts in large quantities while maintaining consistent quality control.
MIM is economically attractive to manufacturers, as well—especially
against parts that require machining. Machined parts require a considerable
amount of labor and a lot of material is lost during the process. When parts
are molded in mass quantities, MIM-type parts can offer substantial savings.
Furthermore, the more complex the part, the more cost reduction the customer
can realize. Its unique process capabilities also allow for advanced fabrications
such as combining components into one complex geometry or co-molding and
bonding dissimilar materials—capabilities that machining and even die-casting
cannot match.
Used to produce intricate parts as small as 5 mm in diameter as well as
larger components, MIM's flexibility in a variety of applications—as
well as cost viability—will most likely continue to drive its continued
growth in the market. Furthermore, new developments and capabilities, such
as three-dimensional shape making with material properties similar to conventional
powder metallurgy, will only help to expand MIM's applications in more
industries across the board.
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