Metal Injection Molding
MDTmag.com 42 / July/August 2014
Metal Injection Molding
for Medical Device Manufacturers
Component fabrication for medical devices must often enable the manufacture of strong, durable parts in in-
tricate shapes and designs. The ability to mold metal in an injection molding process moves developers much
closer to this goal. The fact that the process can be offered relatively quickly makes metal injection molding a
very desirable fabrication method for medical device design engineers.
By Becky Cater, MIM Product Manager,
Metal injection molding (MIM) is a manufacturing process used for more than 25 years to produce
intricate metal parts that have mechanical
properties similar to wrought materials.
MIM is a cost-effective option for prototyping and producing low- to mid-volumes
of medical device components – in weeks,
rather than months.
Combining the flexibility of injection
molding with the durability and strength of
metal, MIM can be used to produce parts
that are difficult or impossible to efficiently manufacture through other means of
fabrication. Part complexity that would be
cost prohibitive due to multiple machining
operations or by casting and then finishing,
can be achieved cost effectively through
The more geometrically complex the
part is, the stronger the rationale for man-
ufacturing it using MIM. Parts can include
irregular shapes, splines, undercuts, side holes
or grooves, or complex contours. Parts that
would typically be made by assembling multi-
ple components often can be designed as a
single MIM part.
It’s even possible to use MIM for low
volume and prototype quantities. Turnaround
times of 15 business days or less, volumes
between 25 and 5,000+ pieces, and low cost
of entry (mold and sample parts for less than
$5,000) are all available with MIM services.
MIM vs. Other Metal-Forming Processes
Compared to machining, MIM offers a
cost advantage for parts with more complex features, an advantage that amplifies
as quantities increase. Because MIM is a
molding process where minimal excess
material needs to be removed, it saves time
and material as compared to machining the
part. This results in time and money savings
for medical device manufacturers.
Investment casting is a labor intensive process that is better suited for producing small
quantities of parts, and typically has a higher
cost-per-part than metal injection molding.
MIM also provides better surface finishes
than investment casting, creating smoother
parts with thinner walls. MIM offers the
ability to scale up production cost effectively,
helping medical suppliers meet high volume
MIM offers superior density and strength
for critical medical components, compared to
conventional powdered metal components.
MIM also provides the ability to produce
more geometrically complex parts for demanding medical applications.
MIM is among the most cost-effective ways
to manufacture highly complex medical parts
in a wide variety of materials. Over the past
15 years, due to its ability to produce high
volume components to net-shape, MIM has
become an essential manufacturing technology for the medical device industry.
Using MIM, product designers select
material properties for their medical application, including hardness, corrosion resistance,
and strength. A variety of metal powders
are used for MIM, and stainless steels are
the most prevalent. The 316L composition
is often used due to its combined strength
and corrosion resistance. Adjusting the alloy
element ratios can also create materials with
MIM enables the production of microsize
parts and intricate medical components with
features such as threads or undercuts that are
not possible using traditional manufacturing processes. Among the first major MIM
applications was orthodontic brackets, which
continue to be a major product for the industry. Typically, these extremely small precision
parts are made from 316L stainless steel.
Another medical application for MIM is
MIM parts shrink about 20 percent into their final size during the debinding and sintering process.