Universal Spool Rewinder and Drybox

Irritated by the stock MMU buffer? Don't want to spend the requisite time, filament and space to print the existing filament rewinders, or have unusually shaped spools? Would you like fast, easy loading and unloading of your filaments, and for them to be kept dry while you're using them? Look no further! Here, I present an almost* totally universal spool rewinder that has very few moving parts and can easily be incorporated into a drybox to keep your filaments both nicely wound and dry!

• I've tested this rewinder on a variety of shaped/weighted spools and have only had issues with a 3kg one I've got. Inner hole diameter is unimportant for this rewinder!

How it works

This rewinder uses friction to wind the rewinder drum while the spool is in use. Once the rewinder is maximally wound, the spool slips against the drum and the rewinder is held in this maximally wound state until unloading begins. As the filament unloads, the rewinder unwinds and coils the spool up. Simples!

Parts List

Printed parts

For each rewinder, you will need:

• 1 x EndCap
• 1 x FixedInnerSpringAttachment

The following items have two varieties: a short version (that can support spools up to 80 mm wide) and a long version (that can support spools up to ~130 mm wide).

• 1 x DrumOuter
• 1 x PassiveRoller
• 1 x SlideyCover (this part is not entirely necessary, but it helps with loading/unloading the spool, as will be explained later in point 3 of "Things to be aware of").

For therewinder holders, you will need:

• 1 x Holder1
• 1 x Holder2
• 1 x Holder3

Note that Holder3 comes in bothShort andLong varieties. I have my rewinders set up with four short drums and one long drum to facilitate a single large spool. If your drybox is too small to allow for this, you can make all rewinders short and use the Holder3_Short option. I haven't madeLong versions of Holder1 or Holder2, but if people want these, I'm happy to post them.

If you are mounting the holders to a table/piece of wood, you don't need the following parts, however if you're putting them in adrybox, you'll need these to fix the holders together and to support the tub so that it doesn't sag under the weight of the five spools. Note that the angle of these (probably) won't fit all tubs so you may need to adjust the angle to suit your tub.

• HolderBasePlateSupport_Narrow (for the ends of Holders 1 and 3)
• HolderBasePlateSupport_Wide (for joining Holders 1 and 2, and 2 and 3)

If you're putting all this in adrybox, you'll need the following parts to support the rod that holds the passive rollers:

• 2 x ExternalRodCap
• 2 x InternalRodHolder

For thedessicant holder tray, you'll need:

• 1 x DessicantHolder
• 2 x Rail
• 2 x RailBoltStressDistributor

And finally, if you're mounting this to the top of the IKEA LACK enclosure, you might want to use these to support the tub while the lid is open. I used 6, but fewer might also work well. They're quite tricky to align if---like me---you don't have the right tools so up to you.

• TubSupportHook

Non-printed parts

Each rewinder needs:

• 3 x square M3 nut (1 for rewinder, 2 for holder)
• 1 x M3 x 5mm bolt (or M3 grub screw)
• 2 x M3 x 20mm bolt (for holder)
• 8mm x (Short = 109mm; Long = 159mm) dowel. Dowel is important here because you'll need to drill into it later.
• 4 x 608 Bearing (I used the ones that came with the MMU spool holders)
• 2 x Torsional springs from badge rewinders. I used the ones from this amazon page and I can't comment on how well other brands will work. Note that if you're making 5 rewinders, you'll need a total of 10 badge springs.
• Some rubbery cover to put on DrumOuter. This needs to be somewhat grippy but not excessively so. The spool should be able to slip over the material without jumping. I used this "Holed mat" from Bunnings, but if you're not in Aus you may have to find your closest alternative. Also, that 450mm^2 piece was enough for fourShort and oneLong rewinder, with a little leftover.

To support thepassive rollers, you'll need an 8mm rod that is as long as your tub is wide. This needs to be somewhat strong to resist bending due to the weight of the five spools. I used 8mm threaded rod from my local Bunnings.

If you're mounting this all in adrybox, you'll also need the following to attach the holders to the HolderBaseSupports:

• 20 x M3 square nut
• 20 x M3 x 12mm bolt

If you're mounting this on top of theIKEA LACK enclosure, you'll need:

• 5 x 1m PTFE tube

And for thedessicant holder, you'll need:

• 1 x laundry bag (or other mesh bag with holes smaller than your dessicant)
• 4 x M3 square nuts
• 4 x M3 x 10mm bolt

Putting it all together

The construction process is pretty straightforward, though getting the springs in the rewinder can be a little fiddly. Hopefully these steps are clear enough to follow:

1. Once all parts are printed, measure out where to drill the holes for the Holders and passive roller support rod for whatever you're mounting it on. If you're using a drybox and mounting above the LACK enclosure, you'll want the passive rod to be 150mm horizontally back and 60mm vertically above the axis of the first roller so that you can open the enclosure lid without the spools falling off the rewinders. One of the attached photos shows these dimensions and another shows how the spools sit when the lid is tilted back. If you're mounting this some other way, itshould work with the passiveroller perfectly horizontal with the rewinder, though I haven't tested this myself.
2. Insert two bearings into each PassiveRoller and one into each EndCap and DrumOuter. If they aren't a perfect fit and you can shake them out, I suggestcarefully supergluing them in place along the outermost face of the bearing.
3. Drill 3mm holes into the 8mm rods ~5mm from each end. These holes should align perfectly with the holes in the Holder part and will be used to fix the dowel in place when the rewinder is in use.
4. Attach the FixedInnerSpringAttachment to the rod. Slide it down so that that the bolt hole is ~25mm from one end of the dowel, with the smaller diameter hub part (that the nut and bolt fit into) on the side of the shorter end of the dowel. The exact placement of this part will be adjusted later. This part should be a tight fit on the dowel, though you may need to drill it out to get it to fit depending on your printer tolerances.
5. Insert the square nut and M3 x 5mm bolt (or M3 grub screw). Lightly tighten to clamp down on the dowel. Don't go too crazy because this will need to be adjusted soon.
6. Insert the dowel + FixedInnerSpringAttachment into DrumOuter. The FixedInnerSpringAttachment part will stop at a small ridge on the inside of DrumOuter.
7. Bend the innermost end of the torsional badge-rewinder springs back over on itself to form a sort of hook shape. Make sure the ~2cm leading up to this end is as straight as possible with few bends or warps. This and (9) are the trickiest steps. Insert the two torsional springs into the slots in DrumOuter. Carefully wind the first spring around until you meet the start of the second spring. Wind both springs so that they don't cross each other until both springs are fully contained inside DrumOuter. 
8. One at a time, insert the end of each spring into the slot on the FixedInnerSpringAttachment. If you followed step 7 correctly, this shouldn't betoo fiddly, though it can still be a challenge for the first few. One of the images shows what this should look like if done correctly (without the dowel). 
9. Test the spring by twisting the dowel to wind up the springs. They should be able to wind up fully until they're both tightly wrapped around the inner hub of FixedInnerSpringAttachment. 
10. Add EndCap to the open end. The slots should fit perfectly into the corresponding slots of DrumOuter. 
11. Check that the dowel can twist freely. There should be little/no friction between FixedInnerSpringAttachment and the ridge on DrumOuter, nor between the springs and EndCap. If needed, carefully adjust the position of FixedInnerSpringAttachment by loosening the M3 bolt. 
12. Once a satisfactory position has been found, tighten the M3 bolt. It could be a good idea to add some loctite or superglue to this bolt, as it will be very difficult to later re-tighten if it loosens over time. 
13. I have found that EndCap tends to separate from DrumOuter if left to its own devices, so I've added a small dab of superglue to bond these parts. Don't go too overboard since you may need to open these later. 
14. Add the rubber mat to the outside of DrumOuter. 
15. Insert square M3 nuts into the relevant holder(s). 
16. Slide the rewinder assembly (the part you just put together) into SlideyCover. 
17. Carefully slide the rewinder assembly + SlideyCover duo into the holder. This can be a little fiddly and you may need to flex the SlideyCover a little.IMPORTANT: make sure the end with the springs is to the right, otherwise the rewinder will be rewinding in the wrong direction. 
18. Insert the M3 x 20mm bolts into the holder and screw them into the holes in the dowel. 
19. Repeat 3-18 with all other rewinders. 
20. The PassiveRollers, DessicantHolder and PTFE tube holes are pretty easy to figure out yourself and writing those instructions would be very tedious. Let me know if you're having a hard time with these and I'll type it out.
21. If all above steps have been followed correctly, you should now have a working drybox + filament rewinder!

You can check the Assembly_All file to see how all the printed parts go together if you get stuck.

Drybox dessicant holder

This was an absolute nightmare to deal with. So many damned hexagons... I'm uploading the .3mf file for my holder, though this would be a fantastic component for someone to remix/upgrade. The current design works well, though it's a lot bigger than it needs to be and the hexagons aren't particularly strong and can break quite easily if you aren't careful.

If you do decide to use my design, you'll need to superglue the three parts together.

You'll also need twoRailBoltStressDistributors to avoid tearing the bolt head through the tub plastic.

Things to be aware of

There are a few considerations that are important to be aware of before using this rewinder:

• Since the rewinder uses friction to wind the spools, as they start to run out, the spool will slip before the rewinder is fully wound, causing the filament to not fully re-spool upon unloading. This hasn't been an issue for me because as the spool runs out, the radius between filament winds and the edge of the spool increases, so the filament never reaches the edge of the spool to tangle on anything. This will only really be a problem for you if you're a stickler for tightly wound spools.
• I've tested theLong rewinder with a 3kg spool and while it fits quite well, the rewinder isn't strong enough to rewind the spool if the drybox is horizontal. I've got my drybox mounted to the top of the LACK enclosure and I've found that the rewinder works with the 3kg spool if the lid is tilted back by about 30 degrees (~halfway to the first notch of the support arm. I used a book to support the lid at this angle). This may work better if you add more springs in the rewinder (there's definitely space in there!) but I've spent too long on this already and it works well enough for me to warrant the effort to fix it.
• The SlideyCover parts are there to manually disengage the rewinder while you're loading/unloading the filament. The rewinder will work perfectly well without these, though you might have a slightly harder time loading your spools.
• To stop the bearings coming out of the PassiveRoller, DrumOuter and EndCap parts, it can be helpful to superglue them in. Obviously, be very careful here to not superglue the bearing such that it can't spin.

Final remarks

Please let me know if you have any confusions about what you need/how to put this together. I've spent quite a bit of time getting to this design and I want to make it as accessible as possible so that as many people as possible can enjoy the greatness that is easy loading/unloading of the MMU.

Good luck and enjoy!!

Print Settings

Printer Brand:

Creality

Printer:

Ender 3

Rafts:

Doesn't Matter

Supports:

No

Infill:

10

Filament: Any Any

Any

Notes:

All parts print without supports.

I used 2 perimeters and 10% infill, but none of these parts are under a lot of stress so you can probably go lower if you want.

I also used a 0.6mm nozzle for some of the DrumOuters and SlideyCovers to speed up the print time.

Category: 3D Printer Accessories