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Putnam Plastics
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New Technology Developed for Fabricating Thin-Walled Urethane Extrusions

Thin-walled tubing produced by Putnam Plastics using its advanced fabrication technology.
Photo courtesy of Putnam Plastics.

DAYVILLE, Conn.--Putnam Plastics, a supplier of polymer tubing for medical applications, recently announced the development of an advanced 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. According to Putnam Plastics, the development of the advanced fabrication technology has provided medical device OEMs with increased design freedom and production capabilities; it has also given clinicians more sophisticated tools for improving the quality of care for their patients.

The motto in many medical tubing applications is "bigger, softer, thinner." 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 NOTES (Natural Orifice Trans-luminal Endoscopic Surgery) and SPA (Single Port Access) are driving device designs consisting of fewer and larger access points, with the ever-present goal to maximize the working space within. These advanced techniques also require considerable articulation of the device within the body with minimal operating forces. For the device engineer, this results in the need to utilize--for the outer body of the device--extrusions that are larger in diameter, have thinner walls, and are highly flexible and durable.

From a functionality standpoint, thermoplastic urethane is a prime choice for such demanding applications, according to the company. However, tremendous challenges must be overcome when considering design-for-manufacturability. "As diameter increases and wall thickness and durometer decreases, the extrusion process becomes increasingly unstable," explained Byron Flagg, product manager at Putnam Plastics. "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."

After extensive development, Putnam Plastics has implemented a proprietary combination of custom equipment and advanced processing conditions to address the challenges that have historically faced the fabrication of this type of tubing. Improved process stability is said to provide a larger design envelope for device engineers, and improved material handling techniques reportedly reduce costs by increasing yields and product quality.

Take, for example, any given 80A durometer urethane extrusion with a diameter greater than 0.5 inch (12.7mm). If the minimum feasible wall thickness had previously been 0.015 inch (0.38mm), it has now been reduced to 0.003 inch (0.08mm), the company says. If the OD tolerance had previously been +/- 0.010 inch (0.25mm), it has now been reduced to +/- 0.002 inch (0.05mm). These tangible improvements are said to reduce tolerance stack-up and allow more efficient device design. After fabrication, advanced handling techniques allow the finished components to move on to the next stage of manufacture, free of defects or contamination.

Putnam Plastics (www.putnamplastics.com) says that its new capability is widely applicable across a broad range of custom extrusion designs, although it has the greatest impact in ODs greater than 0.500 inch and wall thicknesses of less than 0.015 inch in urethane durometers lower than 90A. The custom fabrication technology can be applied cross-functionally and integrated into designs that include features such as co-extrusion, multi-lumen, and wire reinforcement, among others. The result, according to the company, is "a wider envelope of possibility for device design engineers to meet the functional needs of clinicians without compromise."