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Metal Injection Molding(MIM) is an advanced technology,
which allows complex and intricate parts to be produced
in high-volume at a low cost. MIM technology integrates
the shape making capabilities of plastic injection
molding with the material flexibility of powder metallurgy.
It¡¯s an unique technology and a breakthrough in manufacturing
as it provides a low-cost alternative to machining,
investment casting, and stamping, and offers a wider
spectrum of design opportunities which would not have
been possible with traditional manufacturing methods,
ranging from trigger mechanism for firearms to optic
modulators used in fiber-optic networks. Using extremely
fine metal powders, MIM technology produces parts
in high-density and near net-shape with the properties
approaching that of wrought material. Ferro-nickel
alloy, stainless steel, cemented carbide alloy, and
other non-ferrous alloys such as titanium, are common
materials for MIM. |
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Mold Making |
| Molds similar to those used in conventional plastic injection molding are designed and fabricated. CAD/CAM technology is used to enhance the design and fabrication process. |
| Mixing |
| Fine metal powders, thermoplastic binders and other proprietary materials are mixed to form a homogeneous feedstock. |
| Molding |
| Conventional injection molding machines are used to create ¡°green parts.¡± These parts are typically 15-20% larger than the finished product.
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| Debinding |
| Green parts are exposed to heat, solvent or a combination of both to remove most of the binder material. The de-bound are called ¡°brown parts¡±. |
| Sintering
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| ¡°Brown parts¡± are sintered in vacuum-type furnaces. The intense heat shrinks the parts 17-22% to almost complete density, however the shrinkage has already been taken into consideration when the molds are designed. The parts are then complete. Also, secondary machining or surface treatment is available. |
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MIM applications are ideally suited for
components that are relatively complex, very small,
and will be produced in large quantities, at the same
time requiring high strength, high performance and
cost efficiency.
1. Complexity. The components can be created with
complex-geometry features such as cross-drilled holes,
threads and thin walls, usually requiring no secondary
machining.
2. Material properties. Parts produced through the
MIM process are comparable in density and strength
to those made from wrought metal.
3. Tolerances. +0.03mm ~ +0.05mm per cm.
4. Finish. Typically around 4¦Ìm.
5. Quality. Computer controlled automatic production
allow for the parts to be produced in large quantities
while maintaining consistent quality.
6. Cost efficiency. MIM is a cost-effective alternative
to other types of metal processes, such as machining
and casting.
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| 4. Properties of Typical MIM Materials |
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1. Automotive: airbag firing pins, power
window system, safety belts, jacking systems of auto
doors, small gears, auto AC systems, turbo fans racks
of braking systems, and sensors of fuel systems.
2. Firearms: small arms parts, armour-piercing bullet
core, fuzes.
3. IT industry: typewriters, hard disc drive parts,
magnetic cores, axle pins, and porcelain plugs of
fiber optical communications.
4. Tools: drill bits, clamps, nozzles, thread milling
cutters, pneumatic tools, and fishing gears.
5. Medical instrument: orthodontics brackets, laparoscopic
parts like graspers, dissectors, tweezers and instrument
handles.
6. Electronics: Mini motors, connecters, mobile phone
hinges, keys and sensors
7. Other applications: watchcases, watch chains, electric
toothbrushes, scissors, golf heads, jewelry links,
cutting tools and locks.
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