Medical Design Briefs - September 2022 - 38

Why Cleanroom Assembly of Plastic Medical and Electronic
Devices Requires Ultrasonic Welding Technology
F
or years, ultrasonic welding has been used in cleanrooms
where plastic components are assembled to complete medical
and electronic devices. That is unlikely to change. What is
changing, however -rapidly - is the sophistication and complexity
of these products and the level of precision and quality
required to complete their assembly.
Specialized manufacturers know that cleanliness - especially
prevention of particulate contamination - is of paramount
importance, and most have already installed the latest in HEPA
filtration, air pressure, and temperature control and monitoring
systems to comply with all applicable standards. However, it
is equally important for manufacturers to fully understand and
appreciate that today's applications require higher levels of
performance in welding equipment than they did only a few
years ago. Examples of challenging applications include:
* Plastic assemblies containing compressible internal elements,
such as elastomeric seals or cores
* Small, thin, or complex plastic parts welded onto plastic structures
directly atop sensors or delicate electronics
* Components involving posts or other structural elements that
must be ultrasonically swaged or inserted into substrates that
vary in hardness or structural consistency, such as composites
* Parts molded from bioplastics and other novel materials with
narrow processing windows
It is necessary, then, to stay current with available welding
technology. In fact, if ultrasonic equipment is even just seven
years old, it may not be up to the task, and the consequences in
terms of quality and productivity can range from the inconvenient
to the catastrophic.
In ultrasonic plastic welding, parts are brought together under
pressure by the acoustic stack, which generates a vibratory
motion (amplitude) that is transferred to the part. These vibrations
cause friction at the interface between the parts, creating
heat and localized melting to form the weld. Ultrasonic welding
is an inherently clean process, but it does involve moving
parts, and particulate generation is always a possibility. In addition,
quality standards - such as ISO 13485 in medical manufacturing
- demand real-time control, process monitoring,
data storage, and communication capabilities that may not be
built into older welders.
n State of the Art
Today's advanced ultrasonic welders, such as the Branson™
GSX-E1 model from Emerson, incorporate technology and features
that make them ideal for cleanroom applications. For instance,
they are built with electromechanical (servo) actuators,
which are far less likely to generate particulates than pneumatically
actuated units. The new GSX-E1 welder qualifies for an
ISO Class 5.5 cleanliness rating, and, if desired, a special
cleanroom- friendly feature package, which includes stainlesssteel
exterior surfaces to make wipe down easy, can be added.
New power supplies that drive and control the welder also
are drawing interest from cleanroom operators. These have
transitioned in recent years from analog to fully digital systems
that offer closed-loop feedback and tighter control of critical
weld parameters. This change is important because, while the
welding equipment itself is inherently clean, the specifics of
each application - size, cycle times, polymer materials involved,
and so on - influence
particulate generation.
Suppliers can work
with customers to test applications
and determine
the ideal " recipe "
to
achieve high-quality results
while also meeting
cleanliness objectives.
For instance, the Branson
GSX-E1 welder takes
advantage of closed-loop
feedback in the actuator
to make split-second adjustments
to force and
amplitude. Both variables
can be changed in 10-step
increments such that, in a
1-second welding cycle,
for example, the setting
can be changed every 0.1
seconds to ensure optimal
results.
By staying current with available ultrasonic welding technology, manufacturers of medical and electronic equipment find
it easier to maintain the level of precision and quality required in the assembly of plastic components. (Credit: Emerson)
38
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State-of-the-art power
supplies also use web services
to enable remote
Medical Design Briefs, September 2022
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Medical Design Briefs - September 2022

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