Challenges facing medical-device development are being met by a number of players including Battelle Memorial Institute and Teknor Apex Co. that are focused on that market's huge potential.
New technology is pushing the injection molding envelope [in the medical market], said John Clay, a research leader for medical devices at Columbus, Ohio-based Battelle.
We're seeing parts as light as 0.3 milligrams and walls as thin as 0.0004 inches.
But medical molding is different from standard injection molding, Clay added at the Plastics in Medical Devices conference, held April 12-14 in Westlake. Higher-flow resins are required, and there's high-pressure processing with very fast fill rates.
Modifications to tool gating and venting often are needed as well, he said.
Staffers at Battelle's medical unit which employs more than 90 at a 75,000 square-foot location recently did successful troubleshooting on a pair of plastic medical devices.
The first item was a lab on a chip device used for biofluid analysis. Microchannels had to be molded directly onto a small plaque that was only 2 inches wide. The part had demanding tolerances on thickness and flatness, Clay explained.
After resin samples were obtained from eight suppliers, Battelle researchers ended up making two versions of the device one made with a cyclic olefin polymer and one made with a styrenic polymer to provide their client with options having different price points and performance, he said.
Battelle, a nonprofit research and development firm, also helped to develop an early-detection cancer diagnostic device. The item looks like a blood-sample test tube, but has low tolerances on wall thickness and can't have any split-line on its tube axis. As a result, standard injection molding techniques couldn't be used.
Researchers solved the problem by using another cyclic olefin polymer and by performing a complex mold-filling analysis. The device has been patented by a venture capital firm, but isn't yet on the market, Clay said.
At Teknor Apex, a maker of compounds and related items in Pawtucket, R.I., staffers were able to solve a problem focused on a grade of Medalist-brand thermoplastic elastomer used to make an extrusion blow molded bag produced by medical supplier GE Healthcare.
The initial brand of Medalist provided one based on a styrenic TPE was yielding small splits and holes in the bag, which was a single-use anesthesia breathing bag used during surgery to control the flow of air to the patient.
From the material selection process, Teknor also knew that the material had to be soft and pliable, with the feel of latex, according to medical products senior market manager Nick Sandland. It also had to be capable of being influenced by compressed air.
Working with medical-device maker Vital Signs Inc. in Totowa, N.J., Teknor was able to develop the right compound for the job, but it didn't happen overnight.
Both parties were learning as the process evolved, because neither of us had experience to draw on, Sandland said. The compound had to be consistent and tuned to process. We had to control the viscosity and temperature, and had to understand melt characteristics and process variables.
The resulting compound, he said, created a year-on-year productivity improvement of more than 30 percent, as well as less scrap and downtime and, importantly, less conflict with the customer.
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