Fully 3d printed hanging weight scale

prusaprinters

Disclaimer: The project is more or less a mockup from an idea that I got, and haven’t had the time to fully perfect the design. Therefore there certainly will be many design features that needs optimization. Feel free to iterate on the design 😊 The design is based on Hook’s Law, that in short states:  “that the force (F) needed to extend or compress a spring by some distance (x) scales linearly with respect to that distance—that is, Fs = kx, where k is a constant factor characteristic of the spring (i.e., its stiffness), and x is small compared to the total possible deformation of the spring.” (Wikipedia). Because of the linear relationship between the compressed distance of the spring and the weight acting upon it, it’s possible to translate the weight of a hanging object to a linear scale. There will be a difference in print material, printer etc., and therefore I’ve made the design so that you can calibrate the linear scale with the small moveable clips. Start placing a clip onto the measure plate in line with the indicator and with no load on the hook. Next just hang an object with a known mass (ex. 0.5 kg) on the hook and place a clip on the measure plate in line with the indicator pin. Your should be able to place the rest of the clips as a multiple of the first compressed distance cf. Hooks law. It should be able to measure up to 5kg, but bear in mind that this is not a precision scale 😊  I’ve printed all parts from pla with 0.2 layer height, exept for the clips at 0,1. Make sure that the “spring part” of the spring is printed with 100% infill. When assembled you can optionally add a little superglue to hold the upper and lower frames together when not hanging. I’ve printed the project on my Prusa i3 mk3s.