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Downstream extrusion equipment targeted at lines producing small diameter
medical tubing has been re-designed and updated to increase precision and
to make set up and operation easier. Conair recently featured a newly
updated vacuum tank and ‘Med-Line’ puller/cutter in Booth 3939 at the
Plastec-West/MD&M-West show which took place in Anaheim, California at the
end of January, 2008.
The MedLine puller/cutter is a key component for extruders making multi-
lumen microbore tubing used for heart and brain catheters. The software
unveiled at Plastec-West this year includes the capability to
independently control up to eight lumens. A “lumen” is a hollow channel
inside a catheter tube and the MedLine software can control the dimensions
of up to eight of them, without slowing response, without diminishing
resolution or losing repeatability. This unit also employs advanced servo-
drive technology to periodically adjust the outside and inside diameters
(OD and ID) to expand the tube at a point where the catheter would be
attached to other medical equipment. The control then triggers the cutter
blade to cut the tubing at exactly the right place to yield a nearly
finished catheter tube. Nominal outside diameter for this kind of tubing
is between 0.5 mm and 1.8 mm, with wall thickness of 0.2 mm.
“Medical extruders have told us that their key to success lies in
controlling process variables,” explains Bob Bessemer, Conair’s Downstream
Extrusion Product Manager. “With independent position-controlled servo
drives on the upper and lower belts, and twin in-line planetary gear
reducers, Conair has been able to all but eliminate speed variation in the
MedLine puller. When you add the multizone cooling capability of our
HighTech (HT) vacuum cooling tank, plus temperature control units and the
precise material-moisture control of Conair Carousel Plus dryers, you have
a system that provides the kind of control our medical customers say they
need.”
IMPROVED VACUUM TANK DESIGN
The small Conair HT flood-cooling tank includes several new features of
special interest to medical tubing manufacturers. This closed-loop vacuum
controller allows the user to adjust vacuum levels in the tank using a
digital potentiometer.
“Digital vacuum control is inherently more accurate than analog control,”
Bessemer notes, “but we’ve found that extruders prefer to make adjustments
by turning a knob rather than entering a digital setting on a keypad. Our
digital pot works just like the volume controls on a digital radio. You
simply turn the knob until you reach the ideal setting. Depending on the
application, we can change the resolution of the potentiometer so that it
changes in fine increments (2.5 mm of H2O) or coarse increments (25 mm of
H20).”
The vacuum controls (as well as digital controls for the puller), can be
located remotely on hand-held operator-interface panels or at the upstream
end of the vacuum tank. This way, the set-up technician can readily see
the tubing as it enters the tank, even while adjusting vacuum levels and
puller speed.
The interior of the tank has also been redesigned to eliminate places
(like exposed threads) where bacteria and pyrogens (bacterial cell wall
fragments) can become lodged and escape efforts to keep the vacuum tank
clean and sanitary. Other design improvements include:
• Guide rollers that flip out of the way to allow unimpeded access
for stringing of tubing during start-up. Once tubing is positioned,
rollers can be flipped down to hold it in place.
• External water-level adjustment lets set-up technicians fine-tune
water levels with the cover of the tank closed and under vacuum.
• Overflow tray at the upstream end of the tank telescopes in or out
to accommodate cross-heads, in-line dies or melt pumps.
• Ball valves and hoses beneath the tank have been relocated to make
it easier to clean under and around the tank.
The Conair Group, Inc. is the world’s leading supplier of auxiliary
equipment for plastics processors, including resin drying systems,
blenders, feeders and material-conveying systems, temperature-control
equipment, granulators and downstream extrusion systems. Seven distinct
product lines and 450 individual products solve problems, save energy, cut
waste and are easy to use. With long-standing operations in Europe, Asia
and South America, Conair is also an international company. Over 500
employees world-wide bring together 50 years of manufacturing experience
and youthful creativity to break down barriers to innovation and harness
new technology to give customers meaningful, bottom line benefits. The
industry’s most complete product line, top-flight engineering and
unbeatable service… all combine to give processors the confidence they
need to succeed in today’s competitive global marketplace.
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