Typically, manufacturers reach out to TriStar for engineering assistance on material selection or for design enhancements using high performance polymers. That includes wear and friction applications, exposures to severe temperatures or chemicals, or even simple suggestions on how to save money on an existing part. Occasionally, however, we receive requests with unique (or even surprising) requirements, as was the case with a leading medical device manufacturer who came to us to engineer a screw nut that would break ─ but only under very specific conditions!
Engineering Precision for Oncology Care
The customer in this application is a leading manufacturer of medical devices for cancer care, including various imaging devices and advanced systems to deliver targeted radiation treatment. This application is for one of those systems, a dynamic arc radiotherapy system.
The goal was to develop a micro lead screw nut on an 18" long, 3/16” fine thread drive screw. At the end of the screw is a metal plate, one of dozens on the device that can be used to shape a protective shield to protect non-targeted areas during precise radiation treatments. The screw is driven by a small DC motor and needed to be engineered so if the metal plates should somehow jam during adjustment, the nut will snap in half to save the more expensive screw and motor.
The Challenge Was Finding a Material that Met the Wear and Friction Requirements
Our goal was to find a material with the ideal wear and friction properties to ensure the nut broke predictably, while also allowing us to manufacture it at very high volumes. Once we determined what the base resin was going to be, TriStar engineers began the process of trying new combinations of fillers and percentages until the nut reliably broke before the screw or motor did. Throughout the process, geometry adjustments were also made to fine tune the behavior of the nut.
Ultimately, our experience with high performance polymers and our compounding knowledge allowed us to meet this unique challenge. For the first few years of production, we supplied the parts as machined components. As volumes increased, we were able to use the same resin to injection-mold the nut complete out of the tool ─ no additional machining or finishing required.
Partnering with TriStar for Specialized Material Solutions
Our engineering team has extensive experience collaborating on specialized materials and components for a wide variety of critical applications for industries ranging from medical, to aerospace and oil and gas. We can even help with materials that break just when you need them to! As always, we encourage you to reach out to our team if there’s anything we can assist with.
TriStar’s Engineering Partnership with Clients of All Sizes
