Medical Design Briefs - July 2022 - 39

How Automation Can Improve Tubing Manufacturing
A
s the cost of shrink tubing used in the production of
catheters has increased, and supply chain issues caused
delivery delays, FEP shrink tubing, for example, has become
a very expensive throw-away item for medical device manufacturers.
Engineering Resources Group (ERG), a product
and process development company that specializes in automated
processes for fabrication, assembly, inspection, and
testing operations, works closely with clients to determine
the best ways to meet their tubing manufacturing needs.
ERG provides solutions designed to improve client processes
and reduce costs. Some medical device manufacturers
have turned to ERG for machinery to enable them to make
the tubing in house. It can be a painstaking process working
with a delicate feedstock. ERG engineers, however, have developed
a fully automated, self-contained process that is simple
to operate. One key to this development is a unique
puller assembly that deftly handles the fragile tubing as it
enters and exits, facilitating the system's automation.
n How the System Works
ERG has developed a way to create shrink tubing from
regular tubing through a process that includes pressurization,
lubrication, heating, expansion, cooling, washing, and
drying. The first step of the process employs a Versa Caterpillar
puller with pneumatic belt closure, pulling the tubing
from a spool in a controlled way and presenting it to the
system. Powered by servo motors with planetary reduction
gearboxes, the model C-22 pullers are well suited for the
task because they provide uniform pressure and consistent
feed rates. ERG uses a, FDA-approved 40-durometer Neoprene
belt; however, a variety of belt material options are
available to choose from. Although this model puller can
handle speeds of up to 450 ft per minute, the ERG process
generally runs at between 10 and 20 ft/min. Maintaining
that speed is critical so that the tubing isn't stretched or
deformed.
After passing through the first Versa puller, the tubing is
lubricated to ease its journey through the other system stages.
It is heated and then pressurized with nitrogen, which
allows the pressurized tubing to expand. Then the tubing
passes through a water bath for a controlled cooling process
where it freezes in the stress of expansion. Next it enters a
drying chamber before it is pulled by another Versa C-22
Caterpillar Puller on the back end, which presents the finished
tubing to a special automated cutter that produces the
desired lengths while maintaining the pressure in expansion
process.
The C-22 pullers apply just enough pneumatic pressure to
convey the tubing through the system without deformation.
The input and output puller speeds are controlled by the machine
controller with the output puller being primary and the
input puller speed offset as needed to prevent the tubing from
stretching.
The caterpillar design applies uniform pressure over the entire
traction length. Pressure is adjustable, allowing a different
grip on tubing with thicker or thinner sidewalls, for example.
Medical Design Briefs, July 2022
This adjustable, uniform pressure moves the tubing through
the process without any elongation or other deformation.
Compact C-22 pullers fit nicely within the machine's overall enclosure,
as well.
n Pneumatic Actuation Is Key
In addition to the uniform pressure and compact size, a key
aspect of the puller design is its pneumatic actuation. ERG
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39
A Versa Caterpillar puller with pneumatic belt closure pulls the tubing from a
spool in a controlled way. (Credit: Versa Machinery)
Versa model C-22 pullers provide uniform pressure and consistent feed rates.
(Credit: Versa Machinery)
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Medical Design Briefs - July 2022

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