Working closely with extruder and instrumentation suppliers, Conair has been demonstrating its high-performance ‘MedLine’ puller/cutter in a working extrusion line configured to produce the precision small-diameter medical tubing used for heart and brain catheters.
Working closely with extruder and instrumentation suppliers, Conair has been demonstrating its high-performance ‘MedLine’ puller/cutter in a working extrusion line configured to produce the precision small-diameter medical tubing used for heart and brain catheters. Made of a special medical grade of urethane, the microbore tubing is referred to as tapered or “bump” tubing because the outside and inside diameters (OD and ID) are precisely adjusted periodically to widen the tube at a point where the catheter would be attached to other medical equipment. Nominal outside diameter for the tubing produced on the show floor will be between 0.060 and 0.070 inch, with a 0.045 inch wall thickness.
Conair developed the line in its state-of-the-art Tech Center in Pittsburgh and first demonstrated it publicly, in cooperation with extruder supplier American Kuhne, Inc., at the Plastec-East/MD&M-East show in New York City, June 12 – 14, 2007. A similar extrusion line is to be demonstrated in September at an open-house sponsored by extruder supplier Davis-Standard, LLC. Zumbach Electronics Corp. has supplied a laser gauge that continually monitors tubing dimensions.
The key to the performance of this unique extrusion line is the MedLine puller/cutter. The unit employs advanced servo-drive and control technology to precisely vary puller speed and air pressure to produce the tapered bump sections and trigger the cutter blade to cut the tubing at exactly the right place to yield a nearly finished catheter tube. The extrusion line also includes a small Conair HighTech flood-cooling tank, which includes special features required by medical manufacturers. Cooling water is supplied by a Conair portable chiller, and the hygroscopic urethane material is dried prior to extrusion by a Carousel™ Plus W-15 desiccant dryer.
“Medical extruders have told us that their key to success lies in controlling process variables,” explains Dave Czarnik, Senior Tooling/Process Engineer, a fifteen-year Conair downstream-extrusion veteran. “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 in-line gauging, ultra-repeatable cutter response, precise material-moisture control with the Carousel Plus dryer, and the multizone cooling capability of the HT tank, you have a system that provides the kind of control our medical customers say they need.
“Servo-drive and control technology have advanced considerably in recent years” Czarnik continues. “Now we can produce a small medical puller/cutter that is dramatically superior to anything that has been available previously.”
An advanced touch-screen controller uses faster microprocessors and new software to make complex set-ups easy and intuitive. For instance, the controller allows operators to switch on-the-fly from a linear velocity profile to a fully-optimized profile that automatically programs the smooth acceleration and deceleration needed to make tapered tubing or bubble sections. The controller is repeatable enough to meet the most demanding medical standards.
A new kind of puller belt also contributes to the precision of the MedLine units. Instead of a conventional poly-V belt, which tends to slip on the drive pulleys, Conair uses an alternative PD timing belt that is self tracking and does not slip. The new belts are also made of FDA-approved materials throughout, in contrast to conventional belts that must be coated on contact surfaces for FDA compliance. Optional stainless steel cabinet construction also provides cleanliness advantages.
The cutter portion of the unit also features a standard positional servo drive system, which provides cut response repeatability within ±0.1 millisecond — a ten-fold improvement over conventional velocity-based servo systems, which are capable only of repeatability within ±1.0 millisecond. Cut response repeatability relates directly to product cut-to-length accuracy, with fast response becoming especially important as extrusion rates increase. The cutter blade descends from above, which makes it easier to feed cut tubing to discharge conveyers, and the cutter guards are clear so that operators can readily see the condition of the blade or the presence of contamination.
The Zumbach Electronics laser gauge being used in the demonstration monitors OD and ID of the tubing, providing an output signal to the puller control so that the process can be adjusted continually to maintain product quality. If something happens in the process to cause out-of-spec tubing to be produced, the gauge sends a signal that automatically removes the faulty length(s) of tubing from production.
Recognizing that your success in today’s competitive global plastics marketplace is the only true measure of our own performance, Conair is committed to finding and delivering process solutions that make a real difference to our customers. To that end, we listen carefully to learn what matters most to you. We seek to understand the driving issues that affect how you do business today. Then we work to help you transform your business with game-changing products and services that reduce your costs, increase your productive up-time and boost your efficiency.
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