Medical Design Briefs - October 2023 - 48

while expediting the healing process
and restoring mobility. This component
was chosen in a feasibility study to examine
the impact of AFT on a traditionally
machined metal or composite block surgical
piece. The company had a goal of
developing a design that reduced cost
and optimized part geometry. PEKK
was chosen because of its better thermal
performance and hydrolysis resistance,
which is critical given the high heat and
humidity of autoclave sterilization for
medical devices.
Based on the software design and
due to the critical position and dimensional
stability of aiming arm holes for
positioning surgical tools, aligned fibers
(UD tapes) were used to reinforce the
holes. The tapes were also used along
predicted load paths as well as the external
perimeter to strengthen throughthickness
resistance to out-of-plane flexure.
Additionally, stiff face skins were
implemented to create a sandwich structure
surrounding the bulk volume of the
part, which was filled with unreinforced
PEKK. This added step enabled tough
exterior surfaces for post-print deburring,
polishing, and engraving.
The result is a piece that outperforms
benchmark milled aluminum and carbon
fiber reinforced polyetheretherketone
(CF/PEEK) composite block on
cost and weight. Specifically, compared
to benchmark machined aluminum,
the machined composite parts were 22
percent lighter and the printed AFT
parts were 48 percent lighter. The AFTproduced
parts also waste 60 percent
less material than both aluminum or
CF/PEEK, which translates to lower
part costs.
n Conclusion
This technology represents an alternative
solution for manufacturing applications
that can improve patient care.
The surgical aiming arm case study is
just one example of how this innovative
hybrid manufacturing platform can be
harnessed to benefit the entire medical
and surgical manufacturing industries.
AFT opens doors to more sustainable
manufacturing options that can help
lower cost and reduce weight and waste,
all while maintaining the integrity and
strength required of geometrically complex
and small parts subjected to harsh
environments, as surgical instruments
routinely are.
This article was written by Yannick
Willemin, Director, Business Development
at 9T LABS, Lowell, MA. For more
information, visit www.9tlabs.com.
Pulsed Electrochemical Machining for Complex
Medical Devices
PECM works at the
molecular level.
Voxel Innovations
Raleigh, NC
The future of manufacturing technology
may be occurring at the molecular
level, in a process known as pulsed electrochemical
machining (PECM). PECM
is an advanced variant of electrochemical
machining (ECM), a nonthermal,
noncontact material removal technology
capable of small features, superfinished
surfaces, and high repeatability for production
parts. It is a newer, more precise
variant of ECM technology that utilizes a
pulsed power supply.
Simplified, both ECM and PECM work
by utilizing a custom-machined tool
(cathode) shaped as the inverse of the
desired geometry on the workpiece (anode),
and by running an electrolytic fluid
with a pulsed current within the
micro scopic gap between the cathode
and anode. This electrolytic fluid serves
as both the catalyst for the electrochemical
reaction and as a flushing agent that
removes the byproducts of the reaction.
Traditionally, electrochemical machining
has only served the aerospace
and energy industries; however, in re48
A
hole in nitinol measuring 0.5 mm diameter × 10mm deep.
cent years, it has leveraged its unique advantages
to serve the medical device
manufacturing industry and beyond:
* PECM is only concerned with the workpiece
material's conductive properties;
therefore, material hardness is irrelevant,
allowing PECM to machine tough
stainless steel or cobalt-chrome components
at a similar speed to aluminum
or copper.
* As the part is machined with no heataffected
zones or contact with the tool,
PECM leaves a superfinished surface
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quality (0.005-0.04 µm Ra, or 0.2-16
µin. Ra) with no machining marks,
burrs, or recast layers - advantageous
for machining certain implantable
medical devices.
* Another advantage of this lack of contact
or heat between the tool and
workpiece in PECM is that it creates
no tool wear, allowing a single tool to
be utilized in high-volume production
medical devices, such as disposable
surgical instruments, with a high level
of repeatability.
Medical Design Briefs, October 2023
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Medical Design Briefs - October 2023

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