Stroke-Treatment Technology Benefits from One-Stop Plastics Processing Shop

Author: 
Shana Leonard
Diversified Plastics lent its expertise to the manufacture of a catheter manifold
The NeuroFlo catheter for treatment of ischemic stroke required complex machining of the device’s manifold.
CoAxia Inc. (Maple Grove, MN; www.coaxia.com) was established with the intent of pioneering a catheter to reduce neurological damage caused by ischemic strokes. Whereas most stroke-treatment devices attempt to dissolve or remove the blockage, the NeuroFlo is designed to increase overall blood flow to the brain and deliver that blood to the area of the stroke via collateral pathways. “[Competing devices] have all taken the 510(k) route, and they’ve never demonstrated improvement in outcomes with a rigorous, fully randomized clinical trial,” says Rick Kravik, principal mechanical design engineer at CoAxia. “The NeuroFlo is the first device that we know of that has ever been tested in this manner. We’re going the full PMA route for approval.”

Opting to keep costs down during clinical trials, CoAxia sought a vendor that could machine the device’s manifold, thereby avoiding the cost of a production mold until the device was ready for full-scale production. Yet the part quality still had to pass muster in terms of design verification testing, validation, traceability, and consistency.

“We were looking around at different plastic machine shops, but we had one eye on the fact that someday we were going to commercialize this device,” notes Kravik. Multiple shops, however, said that they would no longer be of service once the part was ready for molding. Diversified Plastics Inc. (Minneapolis; www.divplast.com), on the other hand, had the competencies to transition the part from prototype to production. It offered the ability to machine the manifold prototype and then scale-up by building the production mold, molding the part, and performing the postmold pad-printing in-house. The one-stop shop offerings coupled with the supplier’s proximity to CoAxia sealed the deal, according to Kravik.

Being separated by only three miles proved to be advantageous throughout the challenging and iterative development process. Machining the two intersecting, angled cross holes presented a significant stumbling block by leaving pesky burrs, for example. “This excess plastic must be removed or it could break off or cause air turbulence, which will create problems with the function of the device,” explains Annette Lund, vice president, Diversified Plastics. “It is quite difficult to get deep inside of the machined plastic part to make absolutely sure that all the burrs have been removed.” Recognizing the limitations of manual deburring, Diversified Plastics worked with Arrow Cryogenics Inc. (Blaine, MN; www.arrowcryogenics.com) to remove the burrs through a cryogenic tumbling process.

Designed with a central hole that was long relative to its diameter, the polycarbonate manifold also proved difficult to drill while still yielding an acceptable surface finish. But achieving a good surface finish was crucial; otherwise, the rough surface on the inside diameter of the hole could create air bubbles in the glue used during assembly of the end product. “To solve that, Diversified worked out a manufacturing process and tooling that gave us an adequate surface finish without becoming really cost prohibitive,” Kravik praises.

Tooling was integral to the project’s success, concurs Joni Davis, sales engineer for Diversified Plastics. “It sounds like a simple process, but there are multiple through holes and angles that are difficult to hold consistently.” The company had to get creative, employing a special end-cutting mill to help process the clear plastic part without leaving unsightly grinding marks. It also built fixtures to ensure repeatability and consistency among parts produced in the automated process. “Any shop can do one really good part,” Davis says. “But a shop that’s used to holding tight tolerances in their machining of plastics and having that repeatability is what’s key.”