Thermal expansion measuring thingy
Description
This is a little printed meter thingy intended to qualitatively measure the amount of linear thermal expansion in various printing filaments: It's well known that printing in e.g. ABS requires heated beds and a warm enclosure to mitigate against dimension changes associated with differential cooling in the printed part which is not accommodated in strain in the plastic. ABS+ is supposed to be better than ABS, but how much lower is its thermal expansion coefficient? Is one brand lower than another? It is hard to find these parameters on company websites. https://www.simplify3d.com/support/materials-guide/properties-table/ To provide some means of comparing filaments I have designed this...It's a work in progress, as I am yet to get flexible enough living hinges straight off the printer, and in this prototype I have experimented with thinning out the hinge areas using a dremel tool to improve the 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. Perhaps I will add pin hinges or use some bent wire for the pointer ... hmmm. The theory of operation is similar to the bimetallic strip. There is a horizontal beam 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.
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