The Shark (Spool Holder and Retraction Keeper) for Prusa MMU

thingiverse

I have very little space for my setup, but the MMU retracts a lot of filament for the four unloaded filaments. This design incorporates a wallet that sits in the gap between each spool, thanks to some inspiration from TheBall and Abraham.M on the Prusa forums. It keeps the filament from getting tangled on things. I haven't finished building mine yet; I'm waiting on a bunch of parts and finishing my enclosure. However, I've built and tested a single support/panel. Low priority for me but I plan to add: • A brace that clips onto the front just under the filament roller so people can mount them freely without worrying about hitting the end supports and knocking the bearings out. • A table stand - so people can easily mount them on shelves, lacks, etc. • A small clamp to clamp the top corner to the enclosure/wall - just to make them really strong. To build this, you will ideally need: 24-42 x M3 x 3mm brass inserts. These go in the 3mm perspex (or printed panels) (key spots marked in yellow). 24-42 x 10mm M3 countersunk screws. 5 x 10x5x4 bearings (easily available in hobby/printer shops). 10 x M6-PC4 bowden connectors. 12 x M5 nuts and bolts to mount to the wall/enclosure. Length = wall thickness + 10mm. You need 42 fasteners total for six wallets, but three of those fasteners are at the back of the rack behind the spools, so they don't have to be mounted flush. For these you can use standard 12mm M3 nuts and bolts. If you have heaps of space and spools have lots of room for tolerances, use 12mm M3. Next: Clean out support material and make sure the roller hole and filament hole are very clean. If you decide to hit them with a file, keep in mind that there's a small raised bit around the bearing in the roller hole to stop the sides of the bearing rubbing. Don't file that away. Bolt them together. Assemble the panels and panel divider. Use a countersink to clear some acrylic for the countersunk screws. Leave the screws at the bottom loose so you can fit it over the support. Slot the roller on the bearing and slide it into place. Use a plastic pin to hold it in place. There are two different pins with Ø of 5 and 4.9mm. Use whichever one seems best. Should be a tight fit. Screw the bowden connectors into place. Make sure there isn't any plastic dislodged by the connector into the holes. For the lower bowden connector, it is probably worthwhile using a countersink to give it a chamfer. Attach the wallet to the support. Test feed filament through and make sure it moves through smoothly. To calculate your optimum roller length, use ((L - 60)/5) - 0.2. Where L is total length available for the rack in millimeters. eg: 456mm room for rack: 456 - 60 = 396 (room not taken up by the supports) 396/5 = 79.2 mm (space for each spool) 79.2 - 0.2mm = 79mm (leaving a little bit of space for tolerances). Update 31/10/18: Minor update of geometry for the main support to make it easier to remove support. Update 2/12/18: Update of geometry in V2 to make it easier to load filament. The earlier design has issues with rigid filament digging into the side of the 'chute'. I'll merge it with the original Festo design later. Added a new design (Shark main support V2 - no festos.stl) that doesn't require Festos (uses couplers and Festo-less brackets). Instead, it uses rivnuts to hold the PTFE tube. This means that your PTFE tube won't wear out over time as the Festos chew into it. Changed the cage to include a door that can fold down. Makes it easier to load filament. A video showing how to load filament: https://www.youtube.com/watch?v=7BhELwnWRnw