Thermal expansion measuring thingy

thingiverse

This small printed gadget measures the amount of linear thermal expansion in various printing filaments: It's widely acknowledged that printing in materials like ABS requires heated beds and a warm enclosure to counteract dimension changes caused by differential cooling in the printed part, which isn't accounted for in plastic strain. ABS+ is supposedly better than ABS, but how much lower is its thermal expansion coefficient? Does one brand have a lower coefficient than another? It's challenging to find these parameters on company websites. https://www.simplify3d.com/support/materials-guide/properties-table/ To provide a means of comparing filaments, I've designed this...It's still a work in progress, as I'm yet to get flexible enough living hinges printing straight off the printer, and in this prototype, I've experimented with thinning out the hinge areas using a Dremel tool to improve sensitivity by making the hinges more flexible. Of course, this means different prints will have a large variation in sensitivity due to manual post-processing. Maybe I'll add pin hinges or use some bent wire for the pointer...hmmm. The theory of operation is similar to the bimetallic strip. There's a horizontal beam made of two plastic strips loosely fastened together at intervals. The upper strip has a return loop of 0.2mm nichrome wire stuck on top of it using superglue. When energized with 0.5A of current (its impedance is about 10 ohms in total), the wire heats the upper strip, causing the beam to flex downwards. This motion is amplified by the pointer needle and displayed at the top of the dial. The idea is that with a fixed thermal power input to the upper beam, after equilibrium is established, there will be an approximately constant temperature difference between the upper and lower elements of the beam.