Putnam Plastics

Putnam Plastics of Dayville, Connecticut, USA, has announced development of a technology for producing thin-walled, large-diameter, low-durometer urethane extrusions. Commonly used in minimally invasive medical devices, such extrusions have been fraught with manufacturability challenges. The development of this advanced fabrication technology has provided medical device OEMs with increased design freedom and production capabilities and clinicians with more sophisticated tools with which to improve the quality of care for their patients.

Putnam says it has devised a combination of custom equipment and advanced processing conditions to address historical challenges to the fabrication of this type of tubing.  Improved process stability results in a larger design envelope for device engineers and improved material handling techniques, the company says, reducing costs by increasing yields and product quality. The firm gives as an example an 80A durometer urethane extrusion with a diameter greater than 0.5” (12.7 mm). If the minimum feasible wall thickness had previously been 0.015” (0.38 mm), Putnam says its process can reduce that to 0.003” (0.08 mm); if the OD tolerance had previously been +/- 0.010” (0.25 mm), it can be reduced to +/- 0.002” (0.05 mm).

With the continuing evolution of less-invasive surgical techniques, clinicians are pushing device engineers to fit more and more technology through a working channel of limited size. New techniques such as natural orifice transluminal endoscopic surgery) and single-port access are driving device designs consisting of fewer and larger access points that maximize the working space within. These advanced techniques also require considerable articulation of the device within the body with minimal operating forces. Device engineer must use extrusions for the outer body of the device that are larger in diameter, have thinner walls, and are highly flexible and durable.

Thermoplastic urethane is a prime choice for such demanding applications. But there are obstacles.  “As diameter increases and wall thickness and durometer decreases, the extrusion process becomes increasingly unstable,” explains Byron Flagg, product manager at Putnam. “This instability, which results in larger tolerances and lower yield rates, has forced device engineers to compromise their designs accordingly. Even after fabrication, such extrusions are extremely difficult to handle without contamination or damage, resulting in quality non-conformances, higher unit price, and overall lower value for the customer.”

Putnam says its new process is widely applicable across a broad range of custom extrusion designs with the greatest impact in OD’s greater than 0.500” and wall thicknesses of less than 0.015” in urethane durometers lower than 90A.  The company further says it can integrated into designs that include coextrusion, multi-lumen and wire reinforcement.
www.putnamplastics.com