Canadian Plastics

Microbore tubing application for medical industry

A joint project between downstream extrusion equipment supplier Conair and extruder manufacturer American Kuhne Inc. has produced a microbore tubing application for the medical industry.

February 1, 2008   Canadian Plastics



A joint project between downstream extrusion equipment supplier Conair and extruder manufacturer American Kuhne Inc. has produced a microbore tubing application for the medical industry.

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 is between 0.060 and 0.070 inches, with a 0.006 inch wall thickness.

Central to this extrusion line is the MedLine puller/cutter from Conair, which uses advanced servo-drive and control technology to 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. A Conair portable chiller supplies cooling water, and the hygroscopic urethane material is dried prior to extrusion by the company’s Carousel Plus W-15 desiccant dryer.

“Medical extruders have told us that their key to success lies in controlling process variables,” said Dave Czarnik, senior tooling/process engineer with Conair. “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.”

A new kind of puller belt also contributes to the precision of the Med- Line units, Conair said. Instead of a conventional poly-V belt, the company supplied 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, the company said.

The Conair Group (Pittsburgh, Pa.); www.conairnet.com; 1-800-654-6661

Hamilton Avtec (Mississauga, Ont.); www.hamiltonavtec.com; 1-800-590-5546

American Kuhne Inc. (Norwich, Conn.); www.americankuhne.com; 860-886-7745


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