Embedded Files
Design Approach for the Test Fixture
Final CAD of Test Fixture
Final CAD of Test Fixture
Components of Test Fixture
Watertight chamber for swelling test
Load cell fixed into top plate
Adjustable top plate with linear motion shaft and lead screw
Our final design solution is a test fixture based on the ASTM F2789-10 standard, with two main functions: measuring the lifting force and swelling volume of a nucleus replacement device. The fixture includes a transparent watertight chamber fixed to a base plate, and a top plate held in place by two rods (one threaded and one sliding). The top plate can be adjusted up and down using hex nuts on the threaded rod. The test device is placed in a surrogate annulus made of platinum silicone, with a lightweight plunger on top. A load cell, fixed in the top plate and aligned with the plunger, measures the lifting force without contacting any liquids. As the chamber is filled with liquid and the device expands, the plunger presses into the load cell, providing a lifting force reading.
Surrogate Annulus
Surrogate Annulus
The mold was first created in CAD based on the geometries of an L4/L5 intervertebral disc as this is the most common herniated disc. Once the mold was 3D printed, we created a secondary piece to create the cavity for the nucleus replacement device. This was then placed in the mold, and silicone was poured and cured, leaving us with the surrogate annulus
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