Continuous Glucose Monitor Disposable Housing

BACKGROUND // For Type I diabetes, monitoring your glucose levels is a essential part of keeping your disease in check. Especially with children, having real time monitoring of your blood sugar can make management much more reasonable and accurate than constantly pricking your finger to get readings. With a testing deadline quickly approaching, our client needed to add an enclosure for their mechanism with realistic materials that would hermetically seal.

BRIEF // Create a disposable housing that didn’t require any modifications to the molded internal mechanism, screwed together with a quarter turn and hermetically sealed…and do it fast.

TEAM // Mechanical Engineering; Industrial Design

ROLE // Mechanical Engineering

SKILLS // Surface Modeling; Master Modelling

CHALLENGES // As mentioned, this was a quick hit type of project with an accelerated timeline. We were working on some industrial design concepts and had to quickly turn one of them into a reality. This was a great opportunity (at the expense of some CAD challenges) to improve my surface modeling as I encountered some cosmetic surfaces that required some a very specific approach to ensure there were no seams.

There were a couple technical challenges to this project:

  1. We had to have everything mate with the existing molded parts, which made it very difficult since we couldn’t add any features or make any changes to the original parts.
  2. We needed to create an annular seal when the cap screwed down. This meant understanding what type of pressure would occur as a result of the hoop stretch when the cap was screwed down and ensure that we would still get a seal in a Minimal Material Condition and could still screw the parts together in the Maximum Material Condition. This was a tricky problem to try to solve using hand calculations to get us close. 
  3.  We needed to design a thread that could handle this sort of interference. It had to be a quarter turn and use a thread profile that wouldn’t strip when loaded. 
  4. Everything had to designed to be molded with aluminum tooling. This meant CNC machined molds with ball end mills, which limited how small geometry could get. We were also working with a vendor that was only starting to get into internal threads so they required a bit more negotiation and hand holding. Ultimately, I had to help model the cores of the mold in order to help show them which design would have an undercut. 
  5. Since this was a high gloss part, the surfacing was essential to making sure there no parting lines, dimples or non-curvature continuous surfaces, otherwise these defects would be very apparent in the molded parts.