Auto-rewind spool holder (for MMU)

prusaprinters

<p>This is an auto-rewind spool holder that automatically rewinds the spool on filament changes. It replaces the filament buffer completely!</p> <p>When the filament is dragged into the printer, a weight is lifted. When MMU unloads the filament, gravity does the job to rewind the spool.<br/> Check the <a href="https://www.youtube.com/watch?v=TmQAFTuMKQI">video on youtube</a> to see the rewind process or <a href="https://www.youtube.com/watch?v=6MSmuZER7Ww">this video on youtube</a> that shows the "clicking" when the arm is on top during print.</p> <p>All you need is to print the parts and add the bearings that you will have left over from the original MMU spool holders.<br/> You will need some screws to assemble the base to the stands, but any length from M3x14 to M3x40 will do the job. That's it!</p> <p>All the parts print in about 8 hours and don't need any supports. Pretty easy, right?</p> <h3>Supported spool sizes</h3> <ul> <li>Spool width: up to 80 mm (longer versions up to 120 mm available under user g-code)</li> <li>Spool inner hole diameter: 42-65 mm</li> <li>Spool outer diameter: up to 250 mm</li> </ul> <h3>STL files</h3> <p>All the stl files are available on <a href="https://thingiverse.com/thing:3633095">Thingiverse</a></p> <h3>Print instructions</h3><p>I used these super-fast settings to print the parts:</p> <ul> <li>Printer: Prusa MK3S</li> <li>Layer height: 0.3 mm</li> <li>Infill: Use 50% Infill for the bolts. Everything else: 10%</li> <li>Supports: None</li> </ul> <h3>Assembly</h3> <ol> <li>Insert four bearings (8x22x7, e.g. 608ZZ) into the holes in the rod, the cap and the arm</li> <li>Screw the cap on the other end of the rod (the end without without a bearing)</li> <li>Put the bolt with a plus sign into the bearing in the cap with the gear and put the bolt with a minus sign into the bearing at the rod</li> <li>Mount the two stands together with the base and secure them using four M3 screws and square 4 nuts M3nS. You can use any length of screws from 14 mm to 40 mm. </li> <li>Put the arm to the longer stand, so that the bottom side (flat, without the gear) shows towards the stand</li> <li>Put a filament spool on the rod and secure it with the nut. Make sure the filament direction follows the signs on nut/cap</li> <li>Put the PTFE tube that comes from MMU to the filament holder on the base and secure it with the filament cap using two screws M3x10. Make sure to tighten the screws only firmly until the PTFE tube is hold and check with a piece of filament if it can move easily.</li> <li>Put the assembled spool in the holder and load filament to printer</li> </ol> <p>If you want, you can connect several of the spool holders using two M3x10 screws.</p> <h3>Change log</h3> <ul> <li>09.12.2019: added 2 files (*mirrored.gcode) under user print files that allow you to move the arm to the other side. If you do this with every other spool holder, you'll get better spool access</li> <li>25.05.2019: updated bolts that fix an issue that the mechanism is stuck. Use the longer bolt (+) at the side with the gear!</li> <li>23.05.2019: new gcodes with slightly less print time and minor changes. No need to reprint!</li> <li>22.05.2019: changed arm to allow further (manual) rewinding when changing spools</li> </ul>