Medical Design Briefs - June 2022 - 34

Outsourced MIM
Confi dence in the MIM process has
grown in the surgical instrument and implant
manufacturing space. It is ideal for
instruments that require high strength,
wear resistance, and good corrosion resistance.
MIM parts are being used in
many applications, such as minimally invasive
surgery, general surgical instruments,
orthopedic surgery tools, dental
products, and hearing aids. It is particularly
well-suited for surgical instruments
and implants.
MIM is the most suitable manufacturing
process for complex parts that are
used in minimally invasive surgical instruments
being designed for higher degrees
of articulation, which increases the numbers
of complex metal parts used in the
assembly. And metal-injection-molded
com ponents can signifi cantly reduce corrosion
since producing the desired component
as a single part eliminates the
need for brazing or welding, reducing resistance
at the weld. Keep in mind that
the corrosion requirements for metallic
implants are much more stringent than
for medical instruments, making MIM
even more advantageous.
MIM parts are strong and can be bent,
welded, hardened, and heat-treated like
other wrought materials. A wide variety
ADVANTAGES OF MIM
Greater design freedom
With MIM, parts can be designed and
manufactured with minimal design
restrictions. In addition, almost all
design changes are possible within
the shortest development cycle and
turnaround time.
Complex and intricate shaped parts
MIM is ideal for producing complexshaped
components as well as parts
that require assembly or multiple
steps to put together.
High production requirements
MIM is most benefi cial in high-volume
production of small precision
parts with complicated design
geometry. The process lends itself to
automation where high volumes and
consistent quality are required.
Miniaturization
MIM technology is the most viable
process for producing miniature parts
economically.
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PROCESS OVERVIEW
Metal injection molding (MIM) is a hybrid technology that integrates the shaping
capability of plastic injection molding and materials fl exibility of conventional powder
metallurgy. MIM is preferred for mass manufacturing of small, intricate geometric
components of a variety of materials as it can achieve 95-98 percent of its wrought
materials properties at a much lower cost.
Applications
MIM technology has found increased applications in the commercial world - from
home appliances to watches, automobiles to aerospace, and medical devices to
orthodontics.
Materials
Due to the fl exibility of MIM technology, it is possible to customize material compositions
according to the specifi c attributes required by the customers. Compositions
include stainless steels, low alloy steels, carbon steels, nickel alloys, tool steels, and
tungsten alloys.
of metals can be processed with MIM, including
stainless steel, steel alloys,
iron-nickel alloys, cobalt alloys, and ceramics.
Titanium MIM, however, is becoming
the preferred material and manufacturing
method for products with
long life cycles and large annual production
volumes. Many medical engineers
think titanium MIM is prohibitively expensive,
especially for upfront tooling.
However, for high-volume MIM applications,
tooling costs are generally not a
barrier - they are typically recovered
within the fi rst year of production due to
part-price savings.
The highly repeatable nature of the
MIM process produces parts consistent
in size, shape, and strength. However,
MIM typically comes with a longer qualifi
cation timeline when compared to machining
due to the need to build a complex
mold. However, the long-term cost
benefi t makes it favorable.
Manufacturers need detailed knowledge
of the costs and processing associated
with technologies to choose the best
process for each component. Detailed
cost models and process capability data
are needed to compare technologies and
then identify the most suitable process
before manufacturing begins.
Lower Costs than Traditional
Metal Machining
Contours and shapes in medical devices
can be especially complex. Demand
for disposable minimally invasive surgical
instruments has been steadily increasing
as hospitals see a distinct cost
advantage for off-the-shelf, single-use
products that do not require sterilizawww.medicaldesignbriefs.com
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tion. MIM can help manufacturers meet
that increased demand. Injection molding
can be automated when high volumes
and consistent quality are needed.
Using the MIM process, many components
can be produced in a single manufacturing
process that offers great design
fl exibility. The ability to combine several
operations into one process ensures that
MIM is successful in reducing lead times
as well as saving costs. MIM technology improves
cost effi ciency through highvolume
production to net shape, negating
costly, additional operations such as machining.
MIM is scalable from low prototype
volumes to millions of units per year.
With MIM, it's less expensive to mass
produce highly complex parts once a
tool is constructed. Increased costs for
special features - such as internal/
external threads, complex profi les,
chamfers, or identity marking - typically
do not increase cost in an MIM operation
because the features can be built
into the mold. MIM can reduce the need
for secondary operations and reduce
overall raw material costs.
Conclusion
This fl exible, high-quality process arms
medical device makers with the ability to
design unique products without the cost
restrictions associated with conventional
metal-forming techniques. High-volume,
high-performance, complex surgical instrument
parts with strong mechanical
properties are achievable at an affordable
cost with the MIM fabrication process.
This article was written by Steve Santoro,
EVP, MICRO, Somerset, NJ. For more information,
visit http://info.hotims.com/82322-345.
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Medical Design Briefs - June 2022

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