Putnam advances urethane-extrusion designs
January 21st 2010 11:22 pm By Web Development in India
Putnam Plastics has developed technology for producing thin walled, large diameter, low durometer urethane extrusions.
Commonly used in minimally invasive medical devices, such extrusions have been fraught with design 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.
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 Transluminal Endoscopic Surgery) and SPA (Single Port Access) are driving device designs consisting of fewer and larger access points, with the goal of maximising 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 use on 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.
However, when considering design-for-manufacturability, there are tremendous challenges to overcome.
Byron Flagg, product manager at Putnam Plastics, said: ‘As diameter increases and wall thickness and durometer decrease, the extrusion process becomes more unstable.
‘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 historical challenges involved in the fabrication of this type of tubing.
Improved process stability results in a larger design envelope for device engineers; improved material-handling techniques reduce costs by increasing yields and product quality.
Take, for example, any given 80A durometer urethane extrusion with a diameter greater than 0.5in (12.7mm).
If the minimum feasible wall thickness had previously been 0.015in (0.38mm), it has now been reduced to 0.003in (0.08mm).
If the OD tolerance had previously been +/- 0.010in (0.25mm), it has now been reduced to +/- 0.002in (0.05mm).
These tangible improvements 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.
This new capability is widely applicable across a broad range of custom extrusion designs with the greatest impact in ODs greater than 0.500in and wall thicknesses of less than 0.015in in urethane durometers lower than 90A.
As with all of Putnam Plastics’ custom fabrication technologies, this new capability can be applied cross functionally and integrated into designs that include features such as co-extrusion, multi-lumen and wire reinforcement.
The end result is a wider envelope of possibility for device-design engineers to meet the functional needs of clinicians without compromise.