Design News for Mechanical and Design Engineers

Mount Laurel, NJ--Recent advances in materials and processes make short- to medium-run thermoformed medical parts a viable cost-saving alternative to injection molding or structural foam. Further, the process can reduce design-to-production time from months to weeks.

Conversely, injection molding programs can cost hundreds of thousands of dollars for mold production and take nine months to a year to go from art-to-part, notes John Zerillo, vice president of sales and marketing at PPI. Adding to the program's complexity was the need to make more than a dozen part types.

Using PPI's advanced pressure forming techology adds to the appeal of the thermoforming process. The result: the ability to achieve high-quality, highly aesthetic, close-tolerance custom OEM designs with engineered plastics. Even complex components and deep draws present few problems, Zerillo adds.

In basic thermoforming, plastic sheet is produced using heat, pressure, and vacuum to force the hot sheet against the mold face. The amount of positive pressure required will determine whether pressure- or vacuum-forming will perform best. During pressure forming, compressed air pushes the back side of the sheet against the mold, with resulting component features and aesthetics "that rival injection and structural-foam molding," according to Zerillo.

In the case of the blood analyzer, interfacing part tolerances fell within 0.20 inch over the length of a four-ft machine. Even last-minute changes, some coming halfway through the process, saw the tolerances achieved and samples produced on time.

Keeping it clean. And when it comes to an "ultra-clean" product for medical devices, Cyrolite(reg) Q-92, is said to be "the most clean grade of a rubber-modified acrylic multipolymer on the market due to a proprietary technology' performed by its supplier, CYRO Industries (Rockaway, NJ). The Q-92 compound especially is suited for the design of disposable medical devices, according CYRO Technical Manager Peter Colburn.

Colburn reports that the product's benefits include:

- Resistant to yellowing from gamma sterilization.

- Remains extremely chemical and lipid resistant.

- Has high impact strength.

- Processes and bonds easily.

Applications for both Q-92 and other Cyrolite compounds include: filtering housings, chest drainage units, IV accessories, respiratory devices, plasma separators, catheter accessories, urilogical devices, and surgical sutures.