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Integrated Auto-Rewind Spool Holder

by VincentGroenhuis Jul 31, 2019
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First of all gratulations, it is a great design and thanks for sharing it with the community!

I printed it yesterday, but it seems I have a problem or not sure if it is a problem. When turning the spool, after 3 or 4 rotations, the inner part (spring) slips out of the nuts and the tension is lost. (see pictures for what I mean) It is then also not always the case that it jumps in again, so I guess maybe the clearance is too much on my print.

But I'm not sure if that's the way it's supposed to be or if I should just glue it on so that it doesn't happen again.

Hi, did you screw the cap all way in on the hub? Which exact file did you use for printing?

Thanks Vincent for fast reply.
I used the v5.3 Narrow STL and yes I have screwed the cap all way in.

So I think this should not happen and should stay all the time in the same place, right?

Correct, it should stay all the time in the same place. Is your spool narrow enough to freely spin on the hub?
I did not print&test V5.3 narrow myself yet, only V5.2. I remember increasing the clearance in V5.3 so that it is easier to put the springs in the hub, maybe this caused your issues. Anyway you can download OpenSCAD and check the assembly cutout view yourself (60 mm total width, 5 springs, leave rest default) and tune the parameters to reduce the clearance.

Yes, the spool fits really perfect on the hub, I would guess not much, but enough clearance on each side. It spins freely.
Thanks, I will give it a try and play with OpenSCAD. I tried it already with the v.5.4 because there is only the SCAD file uploaded, but I got an error in OpenSCAD. But maybe my version is too old, will update it and try it again.

Yes, OpenSCAD version 2019.05 or newer is required!


I've got version 5.1 that I use with they RepRap Rewinder spool holders in a RepBox2. When I test the spool rewinder by itself, it works great! Now in the RepBox 2 connected to my MMU2S in 3mm I.D. / 4mm O.D. PTFE tubes, I find that the spools only rewind about 30% of the distance necessary to keep the filament from tangling with the other spools. Any suggesting for increasing the distance of rewind ability?

Yes, try 5.3 / 5.4, the spring parameters are better tuned.
Also make sure you don't get elephant feet (compensate in slicer if necessary).
But if there is a difference in using standalone or inside your RepBox 2, then please post a picture and we can look at it.

Thanks for the quick reply. I will print a version of the 5.4 spring to see how it compares. My spring prints did turn out nicely with no elephant foot. I've attached a couple of photos of my current setup.

Is hub/cap rubbing against the stand? If not: I don't know, even V5.1 should at least make one full rotation with spools like yours. Try to find causes of friction and eliminate these. Do oscillation test with/without spool, ...

My main issue appears to be spool slippage. I tried with and without wrapping the spool in black electrical tape. I made a short video. I'd love any further suggestions you may have. Thanks! https://youtu.be/j8QSgvdl8ps

Thanks for uploading the video! It gives a lot of useful information. Several potential causes can be excluded. Some remaining things I can think of is that the springs are too stiff and/or the spool surface too slippery.

V5.1 is definitely quite stiff, later versions have significantly softer springs. Have you tried 5.3 or 5.4 yet? You can also copy the V5.3/V5.4 spring parameters (spring blade thickness and pitch) into V5.1 so that you don't have to reprint all the other parts. Unfortunately Thingiverse has problems with zip files not being updated, so I set an explicit message to download the latest version.

PETG also has a lower friction coefficient than PLA. You tried tape, could it be that your electrical tape is also slippery? Anti-slip surface should make slipping much harder and thus rewind more revolutions.

If you are a scientist then you could also do separate measurements on the spring system (torque versus revolutions) and the slipping element (slipping torque versus spool weight, for different surface type combinations) and check at which number of revolutions the two graphs meet.

I haven't yet tried 5.3/5.4. I will look at that tonight. I may also do as you suggest and copy the spring parameters into my existing 5.1 SCAD to avoid reprinting everything. Let me think about the adhesion issue -- maybe a different tape would be worth trying. While not a scientist, I do try to be methodical and take lots of notes. I will also take a look at the re-mix you mentioned. I'm curious how far that varies from what I'm doing today, as I sized mine to fit the same spool holders (as seen in the video).

Integrated Auto-Rewinder Spool Holder for Repbox

I'll take a look at that as well.

v5.5 is now out: more robust, easier to assemble and better spring parameters for more rewinds.

And I JUST finished creating 5 sets with version 5.4! :(. But! Good news. They are working well. I've got all 5 running in my RepBox 2 right now, doing a torture test of sorts. I've got 3 different spool types loaded. Some spools very full. Others less than half full. Are are rewinding very well! I did also print these 5 with regular PLA, whereas the previous version 5.1 had PLA springs but PETG spools/hubs. I no longer see slippage. I do note that the winding/rewinding seems more "relaxed" which might have to do with why I see less slipping. I did have to manually trim the bottom component that fits into the mated inside of the spool/hub. Not sure if that is something you resolved in 5.5. It was not an issue for me in 5.1. Here is a quick video: https://youtu.be/b5Bg5jk3UdU

5.4 is already a quite good design! If it works fine, just keep rollin'.
Not sure about your clearance issue, depends on why exactly your spring is stack is too big to fit in hub+cap without trimming.

Having some trouble in prusaslicer. It 'repairs' the model by making the notched hole for the axle a solid body and filling it in when I slice. Any ideas?

Which exact file did you use, and do you have a screenshot? I'll look into it later to check if the associated feature was maybe defined incorrectly.

Looks like I had 5.1 and that facet is not defined in manifold mode! It appears to be fixed in 5.3. Thanks a bunch!
EDIT: I lied, the 'wide' version actually still fills in the hole once it slices! Playing around in meshmixer, it looks like there is a zero thickness edge in the wide version which gets defined funky. I added a photo as well. print settings is .2mm quality mk3 not modified from stock profile.

Thank you very much for reporting this issue! I will look at it later and hopefully fix the problem.

Your designs are great and I love all the mods people have done. My question is which of the designs would you recommend for a new MMU2S user? Given all the completely different approaches I didn't want to assume that the newest was the best (unless it is).


The Parametric, Universal, Sisyphus and Integrated version of the Auto-Rewind Spool Holder series all work pretty fine. These differ in technology, style, spool size compatibility and customizability. The most popular one is the Universal rewinder, this is definitely a good start! If you are curious then you can print all four (or five) versions. Only the Original rewinder has a small, rather weak spring, so not recommended for prolonged MMU2 use.

Is there a possibility of adding a direction indicator that could be visible once the hub and spool are assembled for easier identification of the direction in which the filament should go?

Good point. You can use > as top decal character and < as bottom character!

In the file there is only one field/variable to input the emboss character, right? So I can export the parts individually, but not as a set using the 'print' value for output variable, correct? Also, is Hub the top or cap the top?

Correct! We could upgrade the scad file so that in the next version different characters can be defined for top and bottom decals. I consider cap as top, consistent with assembly view. You have to check yourself if it is consistent with the spring orientations so that these wind up in the correct direction (around the axle).

I realized that if there are more than one decal, the < and > characters are mirrored (they don't consistently display as >>>>>> around the hub or cap. Perhaps I can try to use alternating springs so it could rotate in any direction?

Oops, you are right! Will have to add another option, to enable/disable mirroring consecutive characters.
The spring is most robust if all segments wind up around the axle. If you disable springAlternate then the springs wind up both around the axle and to the outer rim. This also works, but is less robust against overloading. Still, it is a good spring so I wouldn't worry too much.

Thank you for your response. I hope to see your improvements in the next versions. In the mean time, I will try it out with springAlternate, but maybe with PETG so it will be a little more durable than PLA. Will decreasing the number of springs(making springs thicker) increase the torque?

Yes! Wider springs = more torque. Spring blade thickness and pitch are also important parameters.

Or use the characters T (=turnwise) and W (=widdershins) to indicate direction!

< and > are now default characters in v5.5

So I finally printed a version that was small enough for the Rep Rewinder, but when I load it with a kilo of Atomic Filament, it just sways back and forth like a pendulum after I've released the tension.

I tried the hack you listed below of wrapping electrical tape along it, and that didn't assist.

Any suggestions?

I attached the scad I used with the settings I modified in it below.

Excellent! The more oscillations, the better. Tape is not needed. Have a watch on the Universal rewinder video: https://youtu.be/03iUbhrU8xw
What exactly is your issue anyway, could you be more specific?

It only goes back and forth by about 1/2 revolution. Even if I wind it until I hear the clutch slipping - >4 revolutions - it only goes forward by 1/2th a spool. After it picks up 1/2th a spool of filament, then it goes back and drops that 1/2th spool of filament, then repeats. When it finally stops it maybe stops having picked up 1/4th a spool of filament.

I haven't gotten my MMU kit yet so I'm just testing by hand, but that doesn't seem like enough to keep the filament from making a mess.

Could you post a video? From your text it is not clear what the exact issue is.

Sounds like normal behaviour to me. 4 revolutions until the clutch starts slipping is good. If you pull more filament then it keeps the spring tensioned. When you give filament back to the spool then it should rewind a couple of revolutions. Did you try this?

There's a lot of bridging on the first spring, the one with the bit that sticks out for the axle, but also has prongs that attach to the layer below. My first print of that spring detached from the bed and looks very rough. Should we print this one with supports?

Just uploaded the STLs of V5.3. This should be easier to print, supports are not needed. If you still have issues with V5.3, please post a photo.

Thanks very much for the quick reply; I really appreciate the work you put into these projects

I've tried to modify the V3 and the V2 SCAD files, but get a rendering that has a ¼ segment removed the full length of the objects. What am I missing?

Set output="print" and re-render :-)

Any chance someone remix this yet to work on the new Prusa Enclosure v2 spool holders? I am building this enclosure now and would like some auto rewinders.

Integrated Auto-Rewind Spool Holder for Prusa Printer Enclosure V2
5 Spool integrated autorewind holder (Prusa style) for MMU2
by toddel

You can download the .scad file, adjust the rewinder length parameter and generate a new STL using the OpenSCAD software. Hope this helps!

If we choose springAlternate=false, which is the preferred direction to wind the spring, around the axle or around the outside rim of the spring housing?

Around the axle, this results in smaller forces on the blade attachment point due to larger distance from center at same torque.

Hi @VincentGroenhuis, I've printed these (and also remixed it quickly with the RepRewind). I have run into one problem with the spool holders I have for filament from a local company. These are a transparent, hard plastic (maybe PC) that is quite smooth. The inner diameter is a hair above 54mm. However, only has 11mm of contact and is not touching diameter of the rewinder for ~30mm. So with smooth surface and only 22 mm of frictionable surface, they tend to slip a lot of friction out. I have a picture of the inner diameter of the spool holder.

Today I will experiment with 'reverse duct tape'...putting some on the inner diameter of the spool. In the mean time, maybe you have an idea.

In theory the friction is independent of contact area so it does not matter. What version of the integrated spool rewinder did you print? V5.1 should provide enough rewinding revolutions even with a slippery spool and without tape.

I'm using 5.1. Yes, the duct tape made a reasonable difference. It's not perfect, but I'm having separate issues with filament that seems to have a bit of a twist to it that is causing it to want to 'jump' off the spool every 15th or 20th load/unload cycle. I also have one of the older ones (a Universal v3.2 or 3.3) that I'm using with the same spool and it is doing same to slight better than 5.1 (the holder with the big nuts that grip/hold the spool).

I should add one more comment, I printed my 5.1's in PETG, not PLA. It's possible there are friction diffrences. I can try to print my next one in PLA.

Electrical tape (the one with a stretchy/rubbery feel) has better grip than standard duct tape, might be worth a try. Also consider the Sisyphus rewinder which is gravity-based, you can adjust the angle of the track to adjust the tension on the filament. Twists in filament are definitely annoying, you need quite a lot of force to avoid the filament jumping off the spool. Slow down filament unload acceleration can help if inertia is a factor.

Sisyphus Auto-Rewind Spool Holder

I tried to modify the length of the hub using OpenSCAD on the v5.1 file and got an error -> Parser error in line 722: syntax error.
l have no idea of how to fix this.

You probably don't have the latest version of OpenSCAD installed. I am using release 2019.5 which introduces new features such as the "each" keyword on line 722.

The next version of the script will verify the installed version number and output a proper error message if it is older than 2019.5.

Thanks for the quick response- you were exactly right.

I currently have 30 spools of filament, and the spool width and hub diameter vary somewhat. My spool widths vary from 64mm to 74mm, and my spool hub diameters vary from 51-63. Is there some tolerance with this version of your spool holder, or would I be better off using the Universal Rewind spool holder (probably the Repkord-specific remix, in my case, as I have a RepBox 2).


No problem at all for the integrated rewinders. Just render one with total hub length (at least) 79 mm, leaving diameter at default, and it should fit all of your spools!

OK, I've assembled one set, and think I now understand. This design does not require the filament spool to tightly fit to the integrated rewinder hub! That's the magic that allows it to work for a range of filament spools. Brilliant! I've been slowing pulling a meter or two of filament off the spool, and watching it rewind as I gently let it rewind while holding on the the end.

The fun fact is that the very first design, the Original Auto-Rewind Spool Holder, also makes use of the same loose hub-spool slipping surface contact method, with the only significant difference being the number of springs!

Excellent, thank you for for the quick reply!

Why are the bottoms of the hub ends mostly elevated off the bed? There's a lot of bridging there. Is it just decorative or is there a purpose? Also will you post the multi-material version? :) Thanks!

From v5.3 the default settings are easier to print. No more many small islands, just a single connected area with decals.

Partly decorative and partly to provide grip in screwing the cap on the hub in case almost the full width is used by the spool. If you don't like it then you can turn the feature off in the scad file.

There is no MMU version, just change color before z=1 mm to get the pictured effect!


This is absolutely fantastic! Thank you for all your development efforts on this. Will you do me a favor and email me when you have a moment? I'd like to discuss some possible collaboration. Thanks! pooch (at) repkord (dot) com.

Yep - I'm definitely looking forward to printing some of these to use in my RepBox 2 with the MMU2.

One of my bearings came out during a print. To harm done, but what is the best way to secure them? A drop of glue?

Did you consider using clips on the axle? These are available in the Parametric and Universal rewinders. Another option is to reduce the bearing hole size to 22.1 or 22.0 for a tighter fit so that the bearings can't fall out. Using glue will also work, but makes it harder to take them out if you need to.

Edit: ideally the hub + clips take up all available space on the axle so that it cannot slide off, if you use a stand with specific length then you could adjust the rewinder length accordingly.

Ok. But I do have to resize the spings also right? Or print more so they fill up the body.

Edit: Never mind. Just found your 90mm design ;-) But even that is not wide enough for the axle, cause the axle from the universal spool holder is 128mm long and that is what I need in the wall-mount.

All dimensions (including spring size) are automatically adjusted based on the parameters entered. So you can set hub length to whatever value you want and let OpenSCAD do the rest.

Cool! Will fiddle with that. I already opened the file in OpenSCAD, but it reported an error. I was using a VERY OLD version ;-) New version works just great!

Glad to hear that!


Have been running two spoolholder for a couple of weeks now. Work great!

But i did find out tonight, that of both spoolholders, the last spring snapped in the middle (see attached photo). Anything you can do to beef this up and make it stronger?

Oops. Yes that can happen. Some ideas:

  • Remove tape on the hub (if you used them), you don't need it in V5.1.
  • Let all springs wind up around the axle and not to the rim. Use springAlternate=true and identify the correct rotation direction.
  • Increase springBladeThickness?
  • Improve scad file so that the spring attachment nearest to the axle is reinforced (this is difficult)

Thanks. Will try your suggestions. I don't use tape, so will try the other suggestions, thanks!

V5.5 is more robust. Spin it in the direction of the arrows and all springs wind up around the axle, no risk of overloading.

Hey, thanks for making this! It's exactly what I needed.

Just a note, the default hubRibDepth = 0.5 is too little for the default extrusion width in PrusaSlicer 2.0.0. The ribs disappear. See the attached picture.

Next I was going to increase hubRibDepth, however this doesn't make the ribs larger, but actually reduces the circle they attach to. As a result, they float in the air.

Lastly it seems the hub holes do not cut out the ribs correctly, there's some material left over, as seen in the last picture.

Mhh, I actually think that last problem is just an unavoidable occurence when just a tiny bit of a rib is outside of where the hole is cut.

There was a bug in the rib generation code causing them to become detached from the hub, it has been fixed in v5.1. If you don't see the new version here then check https://www.myminifactory.com/object/3d-print-97824

I also changed the default hub hole shape to be square for less steep overhang angle, also eliminating loose rib parts.

Ah, thanks Thingiverse, the "download all files" button as usual provided outdated files.

I'm going to check 5.1, thanks!

Can confirm, ribs are fixed now.

I had no issues what-so-ever with the ribs (on v5.0) and Prusaslicer. They came out great.

If you made the rim thinner in v5.0 then the bug caused the ribs to become detached from the hub (mixed up rim thickness with hub wall thickness)