Medical Design Briefs: 2021 Technology Leaders - 42

TECHNOLOGY LEADERS Materials/Coatings/Adhesives
components and complete
the device's protective structural
shell.
* Problem: The close- tolerance
plastic cover must be bonded
gap-free and watertight,
but the weld process and
cover structure cannot ex -
ert undue compressive
force on the sensitive electronics.
Reliance on a
single- factor weld mode,
such as distance, could in
some cases result in excessive
pressure on the cover
and potential damage to
internal electronics.
* Solution: The combined
material density and reactivity
scores in dynamic
mode can optimize distance
mode in each weld
cycle, allowing the actuator
to achieve part-collapse
depth sufficient for watertight
sealing, yet detect
and avoid levels of resistance
that equate with the
compression of electronic
components.
Welding a Sealed,
Elastomer-Core Plug
Consider a sealed, twoway
connecting plug. The
outer shell of the plug consists
of a molded plastic cup
of drilled holes, and molded
insert quality (surface
roughness, flash). Use of a
single-factor weld mode
like energy to deliver precisely
the same force for
each insert could, as a
result of multiple variances,
result in overinsertion and
substrate or insert damage
or result in underinsertion,
misalignment, or pull-out.
* Solution: By augmenting
energy mode with material
density and reactivity
scores, the dynamic mode
feature is able to measure
and moderate the input
of weld energy for each
insert, aiming for a target
condition - a uniform
measure of insert resistance
- that equates with
insert pull strength.
Conclusion
The new dynamic mode in the Branson GSX-E1 2.0 ultrasonic welder from Emerson recalculates
and adjusts welds in real time to compensate for the varying depth and resistance
of compressible plastic parts. (Credit: Emerson)
and lid that contain holes through
which metal connecting pins protrude.
Inside, connecting pins are embedded
in a compressible core of elastomeric
plastic. Because the finished plugs must
be air- and water-tight, the weld-on lid is
designed to compress the elastomer
radially around the connecting pins. A
flat " fit " is essential for the lid, as is a
consistent exposed length for the connecting
pins.
* Problem: The height of the plug's elastomeric
core may vary by up to 10
percent, so achieving consistent positioning,
shell contact, and weld quality
for the lid is very difficult. Use of a
single-factor weld mode like distance
mode would likely result in variances
in the height of the lid/plug assembly
and the exposed length of the
connecting pins.
42
* Solution: The density score in dynamic
mode can adjust for the varied consistency
of the elastomer by requiring not
only that the actuator travels the
required distance but also that it feels
the required amount of resistance (e.g.,
contact with the harder material on the
plug's rim) before welding commences.
Inserting Structural Pins into a
Substrate
Consider the need to insert structural
plastic pins into plastic substrates that
vary in hardness, like composites, while
achieving consistency in insertion depth
and pull strength. The structural pins fit
into grooves essential for assembly of the
larger product.
* Problem: Inserts must deliver consistent
strength despite variability in material
hardness, the depth and diameter
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For many medical device
and medical product manufacturers,
current singlefactor
weld modes, together
with continued advances
in equipment precision
and data-gathering capability,
may well provide adequate
margins of weld,
assembly, and medical
product quality. However,
for manufacturers facing significant or
unexpected application challenges,
such as the need to manage multiple
part- or material-related variables, new
assembly technology like dynamic mode
weld controls may be just what an assembly
process needs. Instead of thinking
about how to redesign a hard-to-assemble
part or augment an existing weld
processes with new sensors, ask an
assembly technology supplier for help.
The solution to an assembly problem
may already be available.
This article was written by Tarick Walton,
Global Product Manager - Ultrasonics for
Branson Welding and Assembly, and
Christoph Manger, Product Manager for
Ultrasonics in Europe, Branson Welding and
Assembly, Emerson, St. Louis, MO. For more
information, visit http://info.hotims.com/
79413-344.
Medical Design Briefs 2021 Technology Leaders

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Medical Design Briefs: 2021 Technology Leaders

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