Overview

One of the long-term projects I worked on at my first co-op was a compression fixture. The fixture was designed to test the gliding force of a syringe when filling a PAQ™, a 3-day wearable insulin delivery device. Coming from classes with limited experience in SOLIDWORKS, I tackled this challenge head-on and learned a lot of designing and manufacturing practices from my supervisor and peers. This fixture went through many design reviews and posed many challenges along the way. At the end, I was able to get it manufactured and implemented for future tests.

Purpose

‣ Remodel an existing fixture to hold the newest PAQ™ device and syringe in a locked position
‣ Design the fixture to be used in two different design verification tests
‣ Ensure the fixture is simple, durable, and precise

Challenges

‣ Documents of the original model was not found in native file type (i.e was an STL file)
‣ The nest of the fixture had to be completely redesigned due to drastic changes in testing procedures
‣ Required near exact alignment of syringe needle and sample fill port, accounting tolerances
‣  No prior knowledge on tolerances nor designing with screws
‣ Must be ordered on a short timeline and be within budget

Results

‣ Authored detailed documentation of SOLIDWORKS assembly
‣ Reduced cost of assembly order by designing for manufacturing
  » Rounded corners and filled in unnecessary cavities
» Simplified model to reduce number of operations
» Selected durable, yet inexpensive material
‣ Assembled fixture and verified its functionality and integrity
‣ Fixture worked as intended for the two governing tests

Lessons Learned

‣ Tolerancing based on desired fit
‣ Integrating off-the-shelf parts into assembly
‣ Ordering and interfacing with suppliers
‣ Adding and subtracting parts in an assembly
‣ Fundamentals of designing with screws
‣ Fundamentals of designing for manufacturing

This is the CAD model of the fixture assembly. The top plate is vertically adjustable and allows for precise syringe alignment. This fixture is used for two types of fluid testing.

 

This is the nest of the fixture. It is designed to hold the PAQ™ faced down and secure it during testing.

 

When fully set up, the syringe needle is able to penetrate the fill port of the PAQ™. This simulates how a client would fill the device with insulin.