Convoluted Kinematic Coin-Sorting Contraption

prusaprinters

<p>Update 11/8/2022: Added STL versions of all the part files (previously I only uploaded 3mf and gcode files).</p><p>This is a coin sorter that uses the weight and size of the different types of US coins to sort them into four columns – 1, 5, 10, and 25 cents. It uses an entertaining system of discs and levers to guide the coins to their correct spots. I've spent weeks tweaking it to get it to work just right with the four most common US coins and it's finally ready to release to the world!</p><p>Here's a demo of it in action (note that this is an earlier prototype with a different design on the coin tray and different colored discs).</p><figure class="media"><oembed url="https://www.youtube.com/watch?v=um1jyPG7XIA&amp;ab_channel=DavidHernston"></oembed></figure><h4>Printing and Postprocessing</h4><p>You will need one of every part except:</p><ul><li>You only need one front window. Choose the solid one only if you can print it transparent. I recommend the designed front window for most people, particularly since it also allows easier manipulation of the mechanics if a glitch comes up.</li><li>You may or may not need three C clips. They help stabilize the rotation of the discs, but I haven't decided whether they're really necessary. I use them, and they're super quick to print, so I recommend you use them too.</li></ul><h5>Materials</h5><p>This project was designed in PLA. The mechanical parts depend on the density of PLA for proper balance. That said, I haven't tried it in other materials and I would be interested to hear others' results. PETG, for instance, has nearly the same density as PLA, so it would definitely be worth a try in that material. The non-moving parts can be printed in any material you like.</p><p>The windows (particularly the front window) should ideally be printed in a transparent material. I wasn't able to get glass-clear results in my experimentation with PETG, but that's the best FDM filament for transparency. If you can print your front window in a resin printer with transparent resin, all the better. I don't have a resin printer, so I'll be interested to see your results.</p><h5>Print settings</h5><p><i>The mechanical parts (discs, wedges, and spars) must be printed with 100% infill for proper balance.</i></p><h5>Assembly</h5><p>Here are some videos to guide you through assembly. Note: these videos are uploading slowly, so they might not be fully processed when I publish this model. They should be available in a few minutes.</p><figure class="media"><oembed url="https://www.youtube.com/watch?v=SiJu5KlG6Fo&amp;ab_channel=DavidHernston"></oembed></figure><figure class="media"><oembed url="https://youtu.be/BpcxuTWwr_A"></oembed></figure><figure class="media"><oembed url="https://youtu.be/72LWhQbNXt8"></oembed></figure><h5>Potential problems</h5><p>The mechanism relies on smooth interactions. The inside surfaces of both windows must be free of blemishes that might interfere with the moving parts. Everything should turn freely with as little friction as possible. The discs should spin smoothly and loosely. The wedges, incline, and rocker should freely return to their rest positions after being rotated. The sync bar should swing on the disc pegs with no resistance. If any of these things aren't true then the mechanism likely won't work properly.</p><p><i>The most common glitch is print flaws that cause unexpected friction or expanded part dimensions (such as overextrusion or acceleration issues).</i></p><p>Even with a fairly well-tuned printer/filament profile, some post-processing may be necessary. If there are blemishes on the inside surfaces of the windows, they need to be sanded away or some other method used to smooth them. If the discs don't turn smoothly then the axles or the axle holes will likely need to be filed.&nbsp;</p><p>I welcome other makers' contributions to the project. If you create a different design for the front window, for instance, I'd love to see it. If you tweak the mechanism to make it more reliable (I've gotten it to 100% reliability in my own prints, but different printers and materials might produce different results) then I'd love to see your changes.</p><p>It should also be possible to adapt the mechanics to other countries' coins (with a little experimentation).</p><p>I created this in Onshape and the project is freely available. Here's a link: https://cad.onshape.com/documents/4f8f9e825816cfd21c913297/w/f0ed94a52a3eb38f9e883bd2/e/a1f67117e52776b11443edee?renderMode=0&amp;uiState=634a61370a53751fab56abd5</p>