3D Printed Vernier Caliper

One of my more challenging 3D printing projects was a print in place vernier caliper , a precision measuring tool. Originally designed in SolidWorks, they were printed on an Objet printer due to the high tolerances required. The final caliper model has a printed tolerance of 0.03mm compared against measuring cubes.

Below is the SW render of the caliper, where each color shows an unconnected internal part, but is designed in such a way that the assembled caliper is printed in a single part.

The ink for the Objet is rather expensive (~$300/kg). Rather than using pristine material, a mixture of recycled and expired material was used instead, which hampered the tolerances of the printed part. As such a large number of prototypes were created to test the tolerances and the manufacturability of the parts. Below is one of the last prototypes, which tested the gearbox, the internal drainage channels (the holes on the sides), and the fit of the rack and pinion. The other prototypes have long since been recycled.

Because of the sub-par material, and the degradation of the material over time, the main pinion has since fractured as shown below. Some movement can still be achieved by forcing the rack and pinion to move, but obviously this movement is not precise.