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ea69

Multiple Mechanism Auto-Rewind Spool Holder

by ea69 Jun 15, 2019
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Hello,

I have designed a leg for your spool holder: https://www.thingiverse.com/thing:4034425. I send to you if you want to add the link.
I have added some pictures here:

TPU Legs for Multiple Mechanism Auto-Rewind Spool Holder

Is it possible your one piece stand could be modified to to work with https://www.thingiverse.com/thing:3742997. That author has a specially adapted stand but it's cut into three pieces. I don't have the necessary screws on hand to hold it together and I've tried several adhesives with no luck. If I could could print it as one joined piece that would be really helpful.

Filament Loader for Multiple Mechanism Auto-Rewind Spool Holder
by mcmaven

i looked at a way to support that mechanism in a modular manner with my base stand and could not come up with a way to do it.

sorry.....

Isn't it possible to just attach one of the two pieces holding the gears in place to the side of the stand as one piece and drill holes for the Base Winder Main piece at the bottom?

it has been a while since I looked at this, so I do not remember all of the part names.

I was hoping to get the central part with the cam modified to mount up like an accessory filament arms using the existing attachment point on the stand. If that was done, the remaining work would be to design a way for the gear/crank mechanism to attach to the side, which would likely require a slight modification of the stand to implement well.

If you want to take a stab at further modifying mcmaven's design so that it would add onto my normal stand, I would be more than happy to work with you on it.

I'd be happy to work with you sometime.

Hi ea69 - I really like this rewinder, but I'm having problems with the track part staying up and getting jammed on the way down. It appears that the bottom teeth of the track don't always mesh with the small gear it contacts and it won't move. I've also tried printing the track with the spring in it just to try another one. Can you suggest anything?

there was an issue with earlier revisions in which the last tooth of the track could balance on the small gear while if filament feeding stopped at just the right time. Making the last tooth on the track shorter solved that problem.

But, I've never had any issue with the track getting stuck at the top of the channel. Can you post a picture?

Does the track (without any counter weight) move freely in the channel if the gear assembly is removed from the stand?

What layer height was your track printed at?

How much counter weight do you use?

Are you using cheap bearings, or nicer ones?

Hi ea69, I am building a set of these ready for when my MMU2S arrives, all is going well but the 12mm bolt and two nuts only weighs 61grms will this be enough? if I add another nut it is still only 79grams which will mean I will need to buy some longer bolts to accommodate the extra nut which is likely to push it up to around 100gms. What are your thoughts, the nuts and bolts are nickel-plated steel.

80-90 grams works for most people.

If you have higher friction bearings and/or unbalanced spools, you might need up to 100 grams.

With very good bearings, you can get 100% functionality with only 65 grams.

Your existing nuts/bolts should work, but are on the low end of the "known good" range.

I would probably buy the longer bolts and additional nuts as insurance if they are reasonably priced.

Thank you ea69, I suppose I could tune it with washers if the longer bolt is too heavy

You should probably get the longer bolt, but initially only use your existing nuts.

An additional nut can be added to each bolt if necessary based on your experience.

There is no need to use washers to find a "perfect" weight that is more than you current nuts, but less than adding an additional nut.

The rewinder is not that sensitive.

Okay ea69, I'll just get the longer bolts, I can get 45mm long that will just hold three nuts which I'm guessing will come in at around 95grms

Can you design a nut and cap suitable for 35mm hub diameter spools?

behn66 made some reducers to allow spools with smaller hubs to be used with the existing cap and nut. Did you take a look at those?

https://www.thingiverse.com/thing:3714696

If those do not work for you, I am sure I can come up with something that will.

mass-cube and adapter for spools with smaller diameter
by behn66

I love the mechanism but I need to figure out a way to reduce the noise, it makes a pretty loud racket when you mount it on top of a hollow LACK table :)

yep....that empty table acts like a resonator. : )

The easiest fix is to attach rubber feet to the bottom of the rewinder stand. A bit of mechanical isolation help a lot.

I bought some cheap anti-fatigue mats and set my rewinders on top of them.

https://www.harborfreight.com/4-piece-anti-fatigue-foam-mat-set-94635.html

There is a very similar but more expensive product made for children's play areas that also works well.

https://www.samsclub.com/p/util-a-mat-commercial-grade-reversible-floor-mats-24-x-24-8-tiles/107930?xid=plp_product_1_2

I've had others tell me they use thick rubber door/entry mats under their rewinders. That seemed like a good idea to me as those are very heavy and still inexpensive.

Finally, I had one guy in the car audio business tell me he used a sound dampening mat on the underside of his enclosure/table. Never got a link to the exact product he used, but I suspect it was something like this:

https://www.amazon.com/uxcell-6-46sqft-Proofing-Insulation-Deadener/dp/B01KAD1XES/

BTW, while searching for the sound mat, I found this:

https://www.amazon.com/DEI-Boom-Spray-Sound-Deadening/dp/B012HIWB40/

Have never tried the stuff, but it seems interesting. After reading through the comments, it seems the product is very similar to spray-in truck bed liner.

https://www.amazon.com/Custom-Sprayable-Truck-Bedliner-Ounce/dp/B07MDL856C/

I reprinted many parts and remade the entire set again, this is probably my final attempt.

Each part is tested individually to ensure the track can drop naturally with gravity so they are all running smooth like butter.

I printed many extra part because with different layer height. Some part are even printed with 0.1 but sadly some are warp so I mix and match a bit at end between 0. 1 and 0.15 parts to find the right combination.

I am pretty sure they will work with rigid material but the real test is those tpu filament. I really hope the previous problems I encounter will not persist otherwise I ready to throw he white towel. I really tried. Lol

holy crap....that is a lot of new parts!

My escape room friend kept my printer busy for days, but I finished the last of his parts yesterday afternoon. So, I am back at it as of this morning.

I did have a few other thoughts after re-reading your posts and thinking our setups and some observations from past testing.

try less weight....I suspect that a bolt and two nuts will be required, but it would be interesting to try just one. Definitely do not start testing with three nuts.

see if the spool is balanced or not before testing....I've had some very unbalanced spools to PLA in the past, but nothing that would keep the rewinder from working. But, TPU might require the spool to be -mostly- balanced. I played with spool balance a bit in the early days of design and came up with a way to test for and correct it.

My test is to put the filament spool on the shaft/cap/nut assembly and to place that on an empty stand (no track and better if no gears also). The spool should rest in any position you place it and not move. If the spool starts to turn when you remove your hand, it is out of balance. Whenever it stops moving, the heavier side will be down. At this point, I attach some weight (paper clips, etc.) to the top of the spool (lighter side will be facing straight up) and test again. Once the spool is fairly balanced, you can attach the weights to the outside of the spool with tape of glue stick.

again, I found that spool balance was not an issue for any normal, stiffer filament. But, it would be interesting to know if you failing spool is unbalanced and if balancing it corrects the issue,

The PTFE tubing I use between the spools and MMU is some really cheap stuff (varying OD and likely varying ID, etc.) and has been reused across multiple designs and now has many "kinks" that have only been mostly straightened out. It is definitely not a glass smooth and low friction solution. I plan to buy some new tubing and replace it soon. But, I am now wondering if the additional if the additional friction in my setup might perhaps be helping with TPU. It certainly seems counter-intuitive. but, it is a variable that i need to test and eliminate.

Yes, having a tighter PTFE tubing does help. I have this cheap chinese PTFE tube that has a smaller ID that provides slightly more friction.

RESULT:
So after 20 min of printing, my black amazon TPU having the filament spewing out from the side again ( i am using one bolt and one nut). Sigh...
My CCtree spool never had this issue and it runs pretty well. I am thinking yellow cctree tpu filament is harder compare to to amazon tpu.
At this point, I am just going to throw the amazon tpu back into my stock buffer system (which it works better).

Balancing the spool certainly helps but ultimately the softer the material, the more difficult for this mechanism to rewind the material. I cannot imagine myself go to the extent of troubleshooting every spool as, It is time-consuming to troubleshoot every spool with this mechanism. if the UNLOAD SPEED can be slow down in conjunction with proper balancing, then I think this mechanism still usable with TPU .

With the current unload speed, very soft TPU may unload faster then the mechanism can rewind. Sadly I cannot figure out where to slow it down.

I would love to hear your thought about all this.

It's a labor of love to get spool balance, I strategically place magnets to balance the spool using the advise you give.

I started a 3 hour long print to see the new balance spool improve the situation. Will let you know how thst goes

Do you know is there any way at all to slow down the unload speed?

Happy Sunday.

So I spent my a good part of my day testing these parts and I want to share with you my finding. All the images are in chronological order and from 0 - 7, they are annotated please take a look and follow along?

Image 0 - All started this morning I printed all the updated parts and I notice the new track don't fit. So i wonder why?
Image 1 - I assemble the new part and the track doesn't appear to drop like the second video. There is a lot of friction keeping the track from sliding and I can feel it.

Image 2. So I took the track v1.2 and tried with the old set up with the gears v1.2 instead of using v1.2.2 - Still, there is a lot of friction.
Image 3. Upon a closer look track v1.2 and gear 1.2.2 I notice the shape was a bit bulky. Maybe is the nozzle?
Image 4. next I tested the spring track with the gear v1.2.2 (printed with 0.6 nozzles @ 0.2 layer height). To my suprise, it runs smoothly.
Image 5. Then I swap the nozzle back to 0.4mm and printed the new track and new gears. This is a comparison shot of all three set.
Image 6. A closer look with part printed with 0.4mm nozzle I notice they fit much better.
Image 7. You can see parts print with 0.4mm nozzle at 0.15 (not 0.2mm) fits quite well.

Final thought, always prints with 0.4mm nozzle for gear parts, not 0.6mm nozzle they deform the shape and that will introduce a lot of friction. As you can see in the close-up shot of image 3. Use better bearing will help, as of right now the seal 608zz bearing uses a heavier grease so it doesn't run as smooth as the more expensive bearing.

Next. I will test the part print with 0.4mm with TPU to see if the new track improves and set up reduces the likelihood of tpu runout during the rewind process.

Will report back soon.

sorry for the slow response.....

I have used a 0.25mm nozzle in the past for some detailed models, but have never tried a 0.6mm nozzle. All of my work on the rewinder has been with the normal 0.4mm nozzle that came with the printer.

The gear pictures you posted from the 0.6mm nozzle are indeed ugly. I am not surprised that things did not fit or run well after seeing those.

The gear tooth profile came from a program called gearotic. I think most people use this software for machining or laser cutting. I simplified the profiles a bit for 3D printing and did have a 0.4mm nozzle in mind when I did it since that size seems to be the most common.

For layer height, I get good results when everything is printed at 0.3mm. The only places that 0.2mm (or 0.15mm) improves the print are: teeth on the track, gear bearing hole in the stand, and the two PTFE arm mounting location in the stand. Thinner layers also eliminates any chance of stray filaments in the threads of the cap and nut. But, that is a pretty rare problem that very few people encounter.

I played with the variable layer height settings in PrusaSlicer to optimize only the areas listed above. Unfortunately, all object on the plate must use the same layer size with variable layers which caused the print time to increase dramatically. As a compromise, my gcode prints the track at 0.2mm (even though only the teeth really need it) and everything else at 0.3mm (leaving some chance that vertical radii on the stand may need cleanup).

BTW, FlamenG updated the spring track this morning, so feel free to grab the new version if desired.

So the bearing does help. So I implemented the new bearing in setup.
The yellow spool in the picture runs fine now, but the black spool's track still had a tendency to get stuck
The track is the same both v1.2. so is the gear v1.2.2 printed with 0.4nozzle @ .2 layer height?

I also tried tinker with the unloads speed, but it doesn't seem to has much of an effect when filaments are loading back into the mmu after being expelled from the bontech gear from the nozzle. Can you shed some like to which parameter actually affect the speed which the filament feedback to the mmu and the mechanism? Having that dail down would help i believe.

Thanks for all your help, it's getting very close.

UPDATE: I printed a new set large, cap, small gear, and bearing insert. I made sure the bearing and all the component fit snuggly now. Before it was the gear was too loose lead to unforeseen friction in the mechanism.

However, I still notice sometimes the mechanism would rewind just a bit too much pulling the filament out the mmu unit. Would you say i play with the weight ratio? Also I still can't figure how to slow down the unloading speed.

There has got to be some small issue with the black spool's rewinder.

For instance, a couple of things in the 2nd picture (20190807_101151) are curious. The cap's bearing does not seem to have been inserted fully. That would make the spool hub assembly a bit wider than normal and cause the stand's sides to be pushed outwards.

The large gear appears to be only slightly engaged with the gears on the cap. This may be an illusion of perspective and not a real problem. For reference, the teeth on the large gear should be completely engaged with the teeth on the cap as shown in the attached picture.

does the last picture (20190807_101059) show the location of the track on the black spool when it was stuck?

Afraid I cannot help with eject settings as that is that something I have ever needed to change....

I received my bearing yesterday and I have installed them. Those bearing is slick compared to my old bearing.
I will try to print something today to test out the new setup.

Variable layer height It is a useful feature :).
For me, I printed my stand in 0.3 to save time. The only downside to that is the bearing hole on the stand won't be perfectly circular but usually, I press the bearing in so that is not a problem for me.

Thank you for asking FlamenG to update the track.

Also if you don't mind me asking, for your set up how many bolt and nuts do you use?

normally one bolt and three nuts.

if a spool is both completely full and unbalanced, I add a 4th nut.

thanks. The unit is working 80% of the time now, but occasionally during the rewind process, it would still pull the filament out the mmu unit.

80% is not anywhere close to acceptable, nor is pulling the too hard so that the filament comes out of the MMU.

we'll keep at it and get it working.

I'm setting up to do some TPU prints and see what results I get. Should be able to test tonight or tomorrow.

That be great, I dont' even know how to describe this situation now.

The spool with the yellow work flawlessly while, the spool with the black tpu would fail 1/5 time during the rewind process. I already replaced the parts so all the bearing would fit snuggly (printed with 0.4 nozzle at 0.2 layer height). Here is my observation.
issue 1: If the track is extending to the highest point occasionally it will fail to unwind, that leads to the stray filament and eventually lead to filament unwind outside the spool will loop around the shaft.
issue 2: Sometime the mechanism will unwind the filament pass a bit too much, beyond the hob gear.
issue 3. once a while the spool will unwind fully pulling the filament all the way back.

This is my observation. Can't wait to hear back from your experience printing with it.

Sounds good :) this is a work in progress. At least one of the spool is working now. Thanks again for the tips you pointed out so far, they have been very helpful.

issue #1 is the real problem. Something is either binding or has too much friction.

issues #2 and #3 are caused by whatever is causing problem #1 sorting itself out in the middle of a filament ejection. #3 is indicative of too much weight.

I'll let you know what I find in my testing....

In the interim, it would be great to diagnose your failing rewinder to some degree. have you tried swapping any of the parts?

For instance, swap the track and weight between the stands and see if the problem stays with the black spool or moves to the yellow.

You could also leave the tracks as they are and swap the spools and hubs (assembled cap, shaft, and nut) between stands and see what happens. Does the problem stay with the stand (potentially indicting the stand, gears, or track), or does it move with the spool?

Just wondering if you got a chance to try the mechanism with flex? Curious to see your finding.

For me, I am still testing as it takes a while to troubleshoot each of those parameters.

completed a relatively simple 2 color print (under 100 tool changes) last night with no failures.

Am picking up another roll of TPU today and will try a three color print (with three different rewinders) tonight.

Hand you got a chance to try the new roll of tpu?

unfortunately not....i have a friend who runs an escape room business and asked me for some help printing props.

will let you know when my printer frees up and i am able to get back to it.

what did you do to get a Flex filament profile that was compatible with MMU printers in PrusaSlicer?

All I did was make a copy of theColorFabb nGen flex filament profile with all of the "compatible printers conditions" deleted under Filament Settings-->Dependencies

I use the semiflex profile and altered its dependencies so I can see it in the multimaterial profile.
I will give the ngen flex profile a try but I will probably lower the filament and bed temperature as I think the default 265 and 80 is too high.

Currentlly, I am reprinting the entire setup again in 0.1mm layer height and see if this problem persists, as switching out each component and do a control test multi-colour will take days if not weeks.

From my observation, there are times when the rewind mechanism will continue to rewind even after filament has completed unloaded from the tube pulling the filament out of the mmu. This happens only with flexible filament, and not with more rigid like PLA.

Lastly, it seems like the tension on the spool also matters (usually factory wind spool works better fails less). For the problematic spool, I am planning to cut away 6 to 7 feet worth of filament and use the remaining spool with the new setup. This might help with the filament being pull out.

It will be extremely helpful, (if you have time) to take a few pictures of your setup. I want to see if there are minor discrepancies that may contribut to a more successful print.

I am pulling my hair out soon if all these interventions don't work.

Lastly,
Thankyou

Cool sent you a DM.

I like your sugguestion change each component to isolate the problem.
I will try your suggestion tonight or tomorrow and get back to you.

I notice large and small gear has been updated to v1.2.2
I am using v1.2 What is the difference should I switch over?

changes were for ease of assembly only, not functional, so no need to upgrade your working rewinders.

when your new bearing arrive, you will probably need to print new gears. I usually break the shaft off the large gear when attempting to disassemble the two gears and bearing. if this happens to you, go ahead and use the current parts.

Just tested the shaft this morning. The funny thing is i printed 4 out 5 track in 0.2mm or 0.15mm layer height. Those run fine.

The only one track I used with the tpu is printed in higher layer height. That actually has more friction and prevent the track from automatically dropping (your second video).

I am going to try another print tonight to test the system. I swap out the track and now it drops smoothly.

Can I offer one small suggestion?
I am currently using the spring track modification and one of the spring fell inside the channel, and I can't get it out. On your next iteration, it would be nice to add a small slot on the side so someone can use a small stick to get the stuck spring out.

the gcode and .3mf i posted at the prusa site prints the track at 0.2mm layer height as some people's printers yield good tracks at 0.3mm and some do not. sounds like you are in the "does not" category... : )

please let me know of the TPU rewinds acceptably with the lower friction track.

I will look into adding a small slot at the bottom of the channel for the next stand iteration.

yes I printed a track with 0.3mm layer height it works. But i think 0.2mm will be safer.

I find with the newer track i get less runout but it still happens.

Reason being my unloading speed could be too fast, so the rewind mechanism can't keep up with the tension while rewinding.

I'll tweak the unloading speed in slicer to see that improve things. As a last option, i can design a guard that attaches to the frame and butt against the spool to prevent the filament runout but that to me is not a real solution.

i suspect the bearings will completely fix your occasional failed rewind with TPU, so do not go too crazy trying permutation of weight and unload speed for now.

Solution #3 should never be required....we will get this working.

To help this process along. I took a picture of exactly how it fails.

Cool, i believe we can get this working :)

two things to try...

i just noticed that the spring track is not current with the normal track. i modified the last tooth on the normal track to make it nearly impossible to catch the track on the small gear as appears to have occurred in your picture. I will work with FlamenG to get this updated. In the interim, please print and test a normal track.

In the picture, your PTFE tube does not appear to be mounted to the stand. I am assuming you just mocked this up to show a failure and that what is pictured is not the way you use it. The PTFE tube definitely needs to be mounted to the stand or an accessory arm using a fitting. Any PC4-M10 pass-through fitting (such as these https://www.amazon.com/gp/product/B01IB81IHG/ ) will work.

Thanks for noticing that. I will replace the spring track right away and give that go.

Yep, that was just for mock-up. This is my current set up, the PTFE tube is attached to a PC4-m10 coupler, and that is position at the halfway point of the filament (see picture). My intention is to let the retracting filament to rub against spool to create more momentum to have that initial kick. I will report back to see if this setup works better.

But first I will print a set of those new tracks and replace my current spring track.

PS: i like the latest version of the stand v1.3 but reprinting them takes quite a bit of filament. Can't commit to that yet until a major revision is release haha. ;)

Thanks for the all the prompt reply and fast communication it's a pleasure to work with you to get this going.
have a good night.

I just printed another track at 0.3mm layer height. It seems to work fine. I think 0.2 will be safer. (I think i printed at 0.35 or 0.4mm thats why it didn't work). YES! it works acceptably with the lower friction track, but I will go back those bearing you recommended and swap them out to rule out any factor of failer. I really want to make this work with printing TPU.

So I am currently printing the sheep file with TPU. The situation has improved a lot but 1 out 5 time the filament still escape the spool.

I think the cause are as follows:
1) unload speed is too fast the rewind mechanism haven't got the time to rewind result excess filament shooting out everywhere.
Solution --> I added additional weight to combat this i'll see if the problem persist, like in my mention in my post, the adding weight can other problem with unloading too much.

Solution 2 --> Tweak the "unloading speed" in slicer so it will unload slower, as a result the filament will tension on the rewind mechanism while unloading back into the selector. I might try 50mm/s as a start, but if you have any unloading speed parameter as a starting point let me know.

I will report back after i try it in my next print. :)

Solution 3 --> It's possible to add a plate guard that attaches to the button of the frame that butts against the spool prevent the excess filament from escaping the spool in case the rewind mechanism can't catch up with the speed which the filament unload. In my opinion, this is the last option if all else fail because I don't feel this address the inherent problem. I can probably laser cut a guard plate at work this week if other attempts fail.

Another note: so far this mechanism works flawlessly with my PLA filament :)

Hi ea69.

I am just wondering if you or anyone has any thought on using this with flexible filament. I tried this setup with my mk3s + mmu2s to pring flexible material last night. I notice during the filament rewind operation, the flexible filament (TPU) is not rigid enough to give it that initial push PUSH to initiate the rewind process. That leads to a bunch of excess filament get push back while not being rewind back to the spool. (I tried adding more weight but sometimes the mechanism still doesn't get the initial kick, but when it does intiate it will create too much momentum and completely unload the filament.

I am wondering what is yoru experience of setting this auto rewind spool holder to work with flexible filament successfully?
Current I have my filament to come up from the top, not the bottom.

I love this design and it works well with PLA no problem.

again, thanks for this awesome design I printed five of them :)

I bought two rolls of TPU filament recently, but have not yet had a chance to test them out (even single material). I'll grab them and run a couple of tests to replicate the behavior you are describing. Hopefully I will be able to find a way to improve the solution for flexible filaments.

In the interim, I do have one thought.......Have you tried upgrading your bearings?

I've seen similar symptoms with PLA when using really cheap recycled bearings of unknown origin in the past. It seemed like the rewinder was struggling to overcome the inertia of the spool and begin the rewind. Adding weight would seem to help some, but felt like a poor fix.

Once I went to higher quality bearings, I never saw this again.

Take a look at the second video on the main page. It shows that the weight of the track alone (no counterweight attached) can overcome the inertia of the cap/shaft/net assembly and generate a full rewind without the filament spool.

Do your rewinders perform similarly, or does the track remain in place when you release it?

BTW, these are the bearings I use: https://www.amazon.com/gp/product/B0094J6GQ0/

The set is expensive ($25), but contains 16 bearings which is enough for a full set of 5 rewinders (with one spare bearing). You might consider giving them (or a similar skate grade bearing) a try.

Hi there,

Take a look at the second video on the main page. It shows that the weight of the track alone (no counterweight attached) can overcome the inertia of the cap/shaft/net assembly and generate a full rewind without the filament spool.

Do your rewinders perform similarly, or does the track remain in place when you release it?"

You have a very good point here, it could be my track is getting stuck. I am using the "spring track". I will check tomorrow taken off all my counterweight to see if my rewinder performs similarly, or whether it get stuck at a particular position.


In the interim, I do have one thought.......Have you tried upgrading your bearings?

Nope i am using generic 608zz bearing similiar to the one in this link
https://www.amazon.ca/Ball-Bearings-SODIAL-Skateboard-Roller/dp/B01EIYJ1U8/ref=sr_1_19?keywords=608zz+bearing&qid=1564905390&s=sports&sr=1-19

I really appreciate the suggestion on the bearing, I will go order a set and $25 dollar a set is reasonable. If this can contribute to the having a better rewind experience I am all for it :)

I am also wondering does it matter if I have the filament loading from top or bottom. In your example, the spool of filament is feeding in the underside. For me, I have it feeding over the top. In my experience, PLA or other rigid material seems to work fine in both orientations. Do you have any opinion or thought about this?

Anyhow, I will take your advice and check my setup and report back :)
Cheers

Comments deleted.

Hi there,

Take a look at the second video on the main page. It shows that the weight of the track alone (no counterweight attached) can overcome the inertia of the cap/shaft/net assembly and generate a full rewind without the filament spool.

Do your rewinders perform similarly, or does the track remain in place when you release it?"

You have a very good point here, it could be my track is getting stuck. I am using the "spring track". I will check tomorrow taken off all my counterweight to see if my rewinder performs similarly, or whether it get stuck at a particular position.


In the interim, I do have one thought.......Have you tried upgrading your bearings?

Nope i am using generic 608zz bearing similiar to the one in this link
https://www.amazon.ca/Ball-Bearings-SODIAL-Skateboard-Roller/dp/B01EIYJ1U8/ref=sr_1_19?keywords=608zz+bearing&qid=1564905390&s=sports&sr=1-19

I really appreciate the suggestion on the bearing, I will go order a set and $25 dollar a set is reasonable. If this can contribute to the having a better rewind experience I am all for it :)

I am also wondering does it matter if I have the filament loading from top or bottom. In your example, the spool of filament is feeding in the underside. For me, I have it feeding over the top. In my experience, PLA or other rigid material seems to work fine in both orientations. Do you have any opinion or thought about this?

Anyhow, I will take your advise and check my setup and report back :)
Cheers

i have some bearings with metal seals similar to those shown at the amazon link you posted. in my experience, the bearings with metal seals have the highest resistance. my guess is that they are made for more of an industrial application and thus are assembled with a heavier grease. but, that is just a guess as I am not a bearing expert.

All of the PTFE exit positions work equally well in my experience.

I placed the order, takes 5 days to arrive I can't wait to see if these bearings makes a different.

I’m brand new to the world of 3D printing, and my new Prusa MK3S & MMU2S I built from the kits. I just printed this auto-rewind setup and I love it! It’s worked very well for me so far, and the simplicity of the track and gear setup is very reliable. I first printed the spring & clutch design auto-rewinder and while it did work, it didn’t always work for me. This version is batting a thousand so far.

I had some odd stringing on my first print of this design, but it wasn’t enough to cause problems with the assembly and use. My second print however was a total fail. My best guess as a complete noob is that the 0.3mm print height will require some more fine tuning of my printer’s settings, but for now I’ve created my own all-in-one layout sliced at 0.2mm. I swapped out the original track with the spring version, and added the high PTFE arm, and the total print time is over 19 hours now. But my first print of this re-sliced version is well on its way and past the issues I saw at 0.3mm layers.

Thanks for an awesome design!

I also built my printer and MMU from kits and believe I understand them better having done so.

Am glad to hear your experience with the rewinder in operation has been flawless thus far.

Let's dig into your print failure....

In my experience printing with 0.3mm layers does not require a better built or calibrated printer.

You called the second 0.3mm print a total failure. In what way did it fail?

Was the failed 0.3mm print one you sliced yourself, or from the pre-sliced gcode I posted on the Prusa Community site? If sliced yourself, was it done using PrusaSlicer with "0.3mm DRAFT" (with all defaults) or another slicer?

I print a lot of prototypes and thus go through a ton of filament. So, I tend to use less expensive vendors. I have run across two spools (out of dozens from this vendor) that for some reason printed VERY poorly (especially the threaded parts).

That experience leads me to ask if all three prints mentioned above (odd but working 0.3, total failure 0.3, and looks good so far 0.2) were produced from the same spool.

Here's a picture showing what happened during my second print at 0.3mm layer height.

really strange....I've never had a print come out like that before and am afraid I do not even have an educated guess, little alone an answer.

No worries! I still love the design, and my 3rd one is printing at home now. Granted the 0.2mm layer version takes quite a bit longer to print, but it's worth the wait for me. Cheers!

I used your .3mf file (complete-set-v13.3mf) and sliced it in PrusaSlicer with the 0.3mm DRAFT settings, though my Filament settings are different than the default with respect to temperature, 215 first layer and 205 for the rest. I'm using MatterHackers Build Black PLA, and all three of my runs thus far are from the same spool. I'll try and get some photos to upload later showing what happened.

I'm wondering if it's the temperature, but basically the filament extrusion didn't stick to the layer below in areas, and got pulled across space inside the threads for the nut and cap. I had some of that on the first run as well, but very little and it didn't render the print useless.

I have no doubt that this has something to do with my setup, as this is the only time I've printed with 0.3mm and have never had issues at 0.2mm or 0.15mm. I just didn't have time to debug, so I decided to re-slice at 0.2mm and turn it loose :)

Thanks again for the design! I will post a picture of the 0.2mm sheet tonight after I get home. I've attached my version of the complete set just for kicks.

Cheers!

Assuming that you can, would you mind sharing the 3MF or AMF file(s) you used to slice the parts for the GCODE file you placed on the Prusa website? I am really interested in how you got the print to go so quickly and how you modified the infill as you did. Watching the print was actually a learning experience. You have some great talent/skills.

Thanks,

RAH

Oh my good! Sometimes I cannot see the wood for the trees!
Thx for the quick help

Have just printed all parts and tried to assemble. is it possible that the stl file for the shaft is wrong?

that picture shows the fully assembled cap and shaft after the bearing inserts have been installed.

one end of the shaft will have a pocket and the other will not. screw the end without the pocket into the cap.

at this point, you should have a pocket on both ends (one in the shaft and one in the cap). insert a bearing into both. then, insert a bearing insert into each bearing.

did you perhaps screw the wrong end of the shaft into the cap?

Greg,

I got my first print working and posted my results to the Prusa maker area. I am wondering if you had thought of a narrower, (shaft and stand), version that would still accommodate Prusa spools (67 to 68mm)? I am trying to fit them into a Samla 22l/6gal dry box.

RAH

I am happy to generate something for you to make your drybox solution work.

What is the width and hub diameter of a Prusament spool?

I can generate any arbitrary width by changing one variable in my Fusion 360 model. I previously released a narrower design that only supported 65mm spools. But, I decided to drop it at 1.0.

There is also a on-off design supporting 60mm spools in which the entire rewinder is only 90mm wide. It was made for cybrsage's rubbermaid container.

Thanks for the offer. I really wanted to find a box that would fit 3 spool holders and not have to compromise your fantastic design. I just broke down and bought the perfect box. See attached. These have built in clips and seals and were $10.50 @ Target/Walmart. And 2 will hold 6 spools and fit onto Lack tables. Easy to configure. Now to make some Silica boxes for the gel.

Assuming that you can, would you mind sharing the 3MF or AMF file you used to slice the parts for the GCODE file you placed on the Prusa website? I am really interested in how you got the print to go so quickly and how you modified the infill as you did. Watching the print was actually a learning experience. You have some great talent/skills.

Thanks,

RAH

I ABSOLUTELY love these! I have tried nearly all the previous ones and they are a bit tricky to get working correctly. I have now printed all 5 to use with the MMU2S and not one single issue. These are much easier to assemble and require less messing with like the previous ones I have tried. Great work~

wow...that is very kind of you to say. I am happy the rewinder is working well for you.

Please let me know if you have any feedback whatsoever and post your make if you get an opportunity.

great design! printed all on ABS and works ok!
not using for MMU2, but for some 1KG ABS spools that got tangled all the time!
some pieces I have to change the horizontal expansion (especially pieces that must put a 608 bearing)...

and like rocky00717 says, a chamfer on spool holder thread will be great.
I'm considering to remix this to use a metal thread rod instead of a printable... and to fix on a 2020 profile instead on holder... so, a lots of modifications (remember, i'm using for other purpose, not for MMU2).

I tested with some bolts and nuts (50g) and it was not enough to rewind a full spool of 1kg... some used spools works great (less than 1kg)...
Have you considered using elastic in place?

Thanks.

also.....it sounds like you are contemplating some serious changes (solid shaft, 2020 aluminum mount rather than a stand, etc.).

I will post STEP files for you if that will make your task easier. (I =HATE= trying to work from .stl files : )

Once I know the design has mostly stabilized, I will probably post a Fusion 360 archive as well.

If you can post STEP files, will be great!
I hate to work with STL files, especially on Fusion 360!

i will get it done before I head to bed tonight.

you are the third person to say they find a rewinder useful without a MMU. It was not a use I had considered, but I am glad it is helpful to you.

You ABS print is the first one I have heard of and it is good to learn it was a success.

What revision did you print? The v1.1 shaft now has a chamfer thanks to rocky00717's suggestion. Does it need more chamfer, or did you print an earlier version?

50 grams is almost certainly not enough weight. 65 grams seems to be the lowest weight that works reliably based on the feedback I am hearing. You should try some weights between 70 and 90 grams.

I got no problem to print on ABS... only on pieces that has bearing... used horizontal expansion (cura), because the space to put the bearing was too tight.
about the bearing, I removed the bearing protection, cleaned (removed all old grease), and lubricated again..

about the "track", got almost no friction with ABS... but even so, I applied a little dry lubricant (ptfe) to improve movement.

I have printed version 1.0! maybe on weekend I try to print v1.1 on ABS...

tried with 50g, 70g, and 100g.. works ok with 100g, but a brand new spool don't rewind like I want...

100g should rewind a completely full 1kg spool with no problems.

One sanity check.....completely assemble the rewinder, but do not mount a filament spool and do not put any weight (or elastic) on the track. Lift the track to the top (last tooth on the bottom of the track is only one in contact with the small gear) and let go.

for me, the track will slowly start to fall and then accelerate until it bottoms out in the channel. The resistance is low enough that the weight of the printed track alone is enough to rewind the cap/shaft/nut assembly.

Does yours do the same?

yes, please print a v1.1 unit. There many improvements for both function and handling/use.

Yes, almost the same result.
Without any spool, and with about 100g, the track slowly start to fall, but don't hit the bottom of the channel. Almost at the end, the track stop (something like 90% of track - sorry, this is difficult to explain because English it's not my primary language).
I will try to sand the channel to see if I get better results.

But with the spool, I got worse results. Maybe the bearings (it's very cheap type), or some type of friction on track / channel.

to be clear, mine will always rewind the empty cap/shaft/nut =without= any weight on the track. I will try to post a video.

As you said, either friction between the track/channel or bearing are the issue (my bet is on bearings).

BTW, not need to apologize for your English. It is immeasurably better than any effort I could ever make at your native language!

I see your video... amazing! my "auto-rewind spool holder" has much more friction... I will try to change the bearings (when I find good quality bearings)

anything which is marketed for use on skateboards or rollerblades is likely to work well. Unfortunately, they are going to cost $1.00 to $1.25 each instead of $0.30 each (50 for $15 deals).

The ones used in the video are "rollerbones" that I got from amazon as an 16 pack for $23.38 ($1.46 each).

https://www.amazon.com/RollerBones-Bones-Roller-Bearings/dp/B07NSV9ZPT

interesting....i never tried a combination of weights and elastic.

I played with quite a few styles of basic office supply rubber bands and many kinds of elastic cords. As I mentioned in the post-printing section, they worked great.

I decided to recommend weights versus cords as it is much easier to describe the right amount to use. Almost everyone has access to a small scale or can just buy a recommended size bolt and nuts. But, the "stretchiness" of elastic is difficult to parameterize easily. I also found that stronger cords needed to be attached at a higher point on the stand (closer to the center line of the spool) than weaker ones. Since both what elasticity of cord and where to attach it to the stand are subjective, I wanted to avoid people having a bad experience.

But, I would encourage anyone want to experiment to try elastic as it is a great solution.

only other thing I'd recommend now is the put a bit of a chamfer on the spool holder thread so its easier to start the cap thread.

agreed....a but of chamfer on both ends of the shaft would make it easier to attach the cap and nut.

I'll make sure that gets into the next revision.

Hi, I just printed one to give a try, I have to say that this design is promising.
I would mention that additionnaly to the shaft, it would be great to smooth out the cap and nut, it is not really a good user experience to get fingers hurted on the first assembly.
And moreover, add a small chamfer to the gears, on the face in contact with the bed, to minimize the elephant foot impact.
I have done these "improvements" with a file and a grinder for this first version and all the assembly is running perfectly flawlessly.
Unfortunately not tested in real life with the MMU2s yet, I wonder if it will spin quick enough during the fast unloading (not in stealth mode). I currently put a 70g M12 bolt with a T-Nut, from my drill press.

thanks for taking the time to try out the design.

I can certainly do some additional smoothing on the cap and nut.

The main purpose of the fillet running down the length of the track was to eliminate elephant foot as it caused a real problem considering the tight fit of the channel.

The gears have been revised for v1.1 (used gearotic to generate them) and now mesh much better. Had not considered that elephant foot was a problem for the gears, but can see your point that it can be. i will investigate a solutions.

I am running about 78 grams of weight and it rewinds quickly enough to keep up with the MMU's rapid ejection on filament unload..

Thank you for the answers.

I have two more comments on the design:

  • The pocket for the bearing of the stand was press-fitting correctly, but it became loose (stand printed in PLA 0.25mm) and now the bearing tend to slide to the point that the big gear rub the flange of the cap, but it cannot fall off.

  • On the very last tooth of the rack and pinion system, I am able to keep the mechanism in a stable position (two teeth facing tip to tip), with the weight at the very top. There is no blocking, a very small amount of force is needed to revive the mechanism since the parts tends to slip very easily, but if the MMU eject the filament exactly at this moment, the rewinder may fail its job. Maybe the rev 1.1 of the gears already solves this issue.

I've only ever printed the stand at 0.3mm layer height and the bearing is always a tight fit. Since the diameter is generated across layers, it is possible that the smoother circle resulting from finer layers could be too loose as you describe. I will investigate.

Yes, it was possible to balance the track on the last tooth with earlier revisions. The profile of the last tooth has been changed to make this MUCH harder to accomplish. But, I am not certain it can ever be completely eliminated. I have not seen this occur during a real print. But, statistics says that it is inevitable that it will eventually occur to someone. Even very rare events do occur once the sample size is large enough.

I have artificially created the failure by hand to see what would happen. The bad news is that the rewind failed on that ejection as expected. The good news is that the system recovered and returned to normal operation on the next use of that filament. (loading rotated the small gear and upset the balanced track).

I am getting a lot of friction on the track. I suspect it is because I used the powder coated bed. Trying again with other bed and 0.1mm

I have printed the track on both sheet types.....The bottom of the track has fillets running down its full length, so not much of the bottom is in contact with the bed to pickup the texture.

does it seem tight in the channel from front-to-back, side-to-side, both, or cannot tell?

its not tight, just a tiny bit of friction. went to the old hardware store and got some 2" bolts and with 3 nuts now it works great!

ok....you had me worried. : )

please post your make if you get a chance.

Rev 1.0 posted.

Even negative feedback is considered a gift, so please share your thoughts and experiences....

Printing a couple of them - I will be able to try them tomorrow.

Nice that now the only part that I have to mirror is the stand and not longer the track :-)

Looking forward for the filament guides to finish my dry box.

the high 45 degree exit is there....i just forgot to mention it in the description or include pictures. i will fix that later today.

Jep, printing that as well, thanks!

I did not noticed initially that you had moved the adapters into different projects.

Dear ea69,
I see an image of a guide in one of the pictures which would allow the PTFE tube to be connected to the stand and filament would be guided at a downward angle (such that it could be on a shelf above the printer and feed down). However i don't see the file for that, any chance you can upload?

Thanks
Charles

The optional files for the filament adapters are indeed missing now. I still have a copy but since @ea69 is finishing a redesign you might want to wait before printing.

Thanks will wait for redesign to print.

Dear ea69,

really nice work. Thanks.

I have remixed it and added a small box on to be attached to your track. The box can be filled with "mass" - so the bolts you mention are not any longer required.
In addition my spool had a very (48mm) inner diameter. This was to small for your caps to center it properly. Have added some adapters as well in mine remix.
https://www.thingiverse.com/thing:3714696

Feedback welcome. Thanks for your excellent work.

mass-cube and adapter for spools with smaller diameter
by behn66

thank you for trying my rewinder and even more importantly for improving it.

The mass box and diameter reducer both look very good to me.

I'll be posting a major update later today (finishing the final test run and working on instructions). However, I believe that both of your additions will still work on the new version without any changes.

Another question: is there a reason for not having a different convertion ratio in the gears so that the same track length results in more spins of the hub? Adding more weight would be simple and I would expect the gears to be able to handle.

Most likely the MMU2 has enough with the current 2 spins but wondering if having a 3rd spin as reserve would not be good if there are no disadvantages.

unfortunately, there are some disadvantages...

the pitch of the gear teeth must remain constant for everything to mesh correctly. The outcome is that a gear with fewer teeth has a smaller circumference. That creates a practical limit on the gear ratio in this situation.

I tried going to 6 or 8 teeth on the small gear (from 10). They did not mesh well with the track and the parts were pretty flimsy (all teeth, no hub).

I also looked at adding more teeth to the large gear. That worked well, but caused a different problem.

The only part of the track that matters for generating rewinds is the track below the small gear. This length determines how far the counterweight can be raised to store energy.

Adding teeth to the large gear increases it circumference. The larger circumference means the diameter is also larger. This moves the small gear towards the base of the stand. The length of track below the small gear becomes smaller as the gear moves down the stand. This reduces rewind length, offsetting the gain in rewind length you wanted to achieve by adding teeth in the first place.

The only solution is to increase the track length below the small gear by making the stand taller. BTW, making the stand taller without changing the gears also yields additional rewind, so why bother....

The last thing investigated was placing the gears above the cap. This resulted in an even taller stand as you must have quite a bit of channel above the small gear to stabilize the track at full extension. It also complicated the loading and unloading of spools.

I was thinking in increasing the diameter of the cag gear while at the same time decreasing the diameter of the large gear atached to the track gear so the usefull track length stays the same. From your comment it looks like there is a limit on the ratio you can obtain.

Would any other teeth design help? I see triangular teeths being used for gear reductions with factors 3:1 being common.

I am being curious here - the current design with close to two rotations works fine!

now that I have a reasonable 1.0 version released, I am looking at upgrade possibilities, including additional rewind. Will let you know how it turns out.

Thanks a lot for this great design! I was getting mad with the spool getting tangled with the Universal Rewinder on complicated parts (with a low of filament changes). So replacing all my holders with your design.

A few requests:

  • larger stand: I have a few 2 Kg spools and was using the larger 3 Kg Universal rewind holder.
  • an adapter for 45° with the filament leaving upwards? I am using this filament guide (https://www.thingiverse.com/thing:2896547) to place my spools in a dry box that sits under my printer.
  • a larger nut: some spools have a central hole with a larger diameter than your nut. I tried the nuts from the universal holder (I have a lot of those) but your hub is a bit larger so they do not work...

Another small request: if you could version the files you upload it would be easier to find out which parts have changed when you do changes. I would want to benefit from your newer improvements by only printing those parts which changes.

Thanks in advance!

Angled dry box filament guide

apologize for the versioning as I should have thought of that. I've been making daily improvements based on feedback. There is a log in the revision history. But, that does not track which parts were affected by each change.

I am test printing what I believe will be my last major revision, so it would be best to hold off until tomorrow before kicking off your prints.

How wide are the 2Kg spools? My model is parametric, so I can generate a new stand and threaded shaft to support any width spool by changing a single number.

What diameter hub would a larger nut (and cap) need to support? I've already been told there is a need to taper both nut and cap more quickly so they work better with smaller hubs. Enabling a larger hub and tapering down more quickly will both increase the overhang angle on the cap. This cannot get too steep or the part will require supports. I'll see what I can do once you give me the diameter....

That is a neat dry box solution which I had not seen before. A high fitting location with a 45 degree upwards angle is no problem. I'll post one with the next revision.

Comments deleted.

Thanks for the warning: I will let the printer "sleep" this night and check for new versions tomorrow :-)

The 2 Kg spool is 30 cm in diameter. Its inner hole is 6 cm.

The spool with the large central hole has a diameter of 7,5 cm. If it is too much to get into a single nut I was thinking in an "adapter ring" that could be added to the current nut to extend its external diameter. This way the virtual "large" spool could be printed in two parts and actually used only when needed instead of having two types of nuts.

Thanks in advance for the 45° adapter. It will allow me to keep 4 spools in rather small box of 50cm x 30 cm. I will share some pictures when ready.

wow.....I've never seen a spool of filament that large.

Will be interesting to see if the weight required changes with something that large or not.

Since it is 300mm in diameter, I assume it is not that much wider than a 1Kg spool that has a 200mm diameter. Is that right?

Right, is the same wide than the 1 Kg spools. I would expect the same hub to work fine: at least is does with the universal adapter at https://www.thingiverse.com/thing:3369189 . It might ventually need more than 90 g weight to turn but that is easier with just a larger bolt.

Btw: I mirrored the stand and the track in order to get two stands together and with the fillament exits as closer as possible. It works fine and allows a better distribution in the dry box.

Large stand for 3 kg spools on Universal Auto-Rewind Spool Holder

just posted a revised stand and track which supports 300mm spools at http://www.thingiverse.com/thing:3759144

Stand and Track Supporting 300mm Spools for Multiple Mechanism Auto-Rewind Spool Holder
by ea69

I love this idea!

But am I missing something or do the STL files for the stand not look like the pictures. There's no opening for the track to move through.

that is me being an idiot and posting a bad .stl file. was making some edits in fusion, got the change to a point I was happy with it, and exported the .stl

unfortunately, I forgot to wind the timeline all the way to the end first....So, every step after my edit (including all the steps where the track's channel get created) were not in the exported model.

I re-exported all the models and uploaded them just in case I made a similar mistake on another part.

sorry for the confusion and hassle........

No worries, I've done that too.. Thanks for the quick fix.

Where in the world did you find M13 nuts and bolts? I've checked every industrial supply I can think of; they all go from M12 to M14.

While it's a small list, if you could include a BOM with the links, that would be amazing for those of us who, apparently, lack the prerequisite Google Fu skill to find Jack and/or Schitt. I also cannot tell what length bolt you've used, so the BOM would help in that, too. It would also allow me to make sure that my weights are as equal to yours as possible, which would make it easier to trouble shoot later.

Thanks for your time, I love this design. Way more repeatable than a printed spring, and way cheaper than a custom wound metal one. In fact; as long as gravity doesn't go away or change drastically, it should be relatively repeatable for at least a few billion years!

I use M12 bolt with hexagonal head and 25 mm length. With one M12 nut it makes 50g weight with space for another nut (+15g) if necessary.
The 50g weight works well for me.

The truth is that I am located in the US where metric hardware is hard to find and expensive. So, even though I design everything in mm, I have no idea what the "common" metric fastener sizes are.

I have updated the description to be explicit about what fasteners I am using and their total weight.

The important thing is to hit the target weight, not how you get there. Nuts and bolts are commonly available and easy to attach. But, anything dense should work.

Thanks for the compliment. I worked hard on this and am happy with it so far. I certainly would not have come up with this idea without learning from and leveraging the work of others.

I feel pretty comfortable about gravity lasting longer than any print I might undertake. : )

My long term concern is breaking teeth off the small gear or track (which is why I printed them in more durable PETG rather than more rigid, but brittle PLA).

I feel you, same here. I try to buy in metric just in case I need it for something else in this wonderful engineering/robotics field (Though I have no idea what I could possibly need 13mm nuts and bolts for...), but if I gotta go for the inch standard, I guess I'll bite the bullet... I feel dirty, though. I just won't tell my printers... shh.

Thank you for getting the weights for me, that was more critical than anything, I agree. I might even try just making a pause-and-fill 3D printed ballast that uses steel shot... once I figure out the exact cubic volume of the weight in .177 steel shot... I just gave myself a project, didn't I?

I might play around with the design with the teeth and see if I can't come up with a way to rigidify (I swear it's a word... Even though my browser disagrees) them, because I see what you mean. If I come up with anything, I'll remix it, for sure.

Thanks again.

I have quite loose fit of the small gear on the shaft of the large gear. According to the model, there is 0.45 mm tolerance in diameter of these parts which seems to be too much.
However your model looks very promising. I can imagine some detachable arm for festo fitting which could connect on either side of the stand with possibility to attach festo for PTFE tube from the front or the bottom of the arm. This would make your spool holder an universal solution with option for filament feeding from bottom of the spool (holder on table with the printer) or from top of the spool (holder on shelf above the printer with oposite direction of spool rotation).

thank you for your feedback and the kind comment.

Yes....it is 0.45mm. The shaft is 7.85mm (to achieve a good fit to the 608 bearing) and the ID of the small gear is 8.3mm. This was originally 8.1mm, but the fit was too tight on my prints, so I enlarged it. For me, this is still a tight press fit, but can be done with my hands.

Let me print another set and verify I have not made some mistake between printing my units and exporting the .stl files for thingiverse.

Does the shaft of you large gear fit the bearing well?

I will look into a detachable high arm which would allow taking filament from the top of the roll on the opposite side. BTW, filament removal must always spin the spool in the same direction regardless of where the festo fitting is located. The gear and weight system is not bi-directional.

You are right about direction of spin but look at the picture. Maybe it better describes my idea. Depending on side of PTFE tube connection the filament can be taken from bottom or top of the spool which gets you more possibilities of spools arrangement.

thank you for the picture as it really helps. turns out i partially understood you.I thought you were looking for something like the attached markup of your picture.Let me see what I can come up with now that I understand what you are looking for.

I have spent some time on this and know what is going on. But, that does not mean I understand it.....

I'm going to wager that you use PrusaSlic3r and that the 608 bearing is a very loose fit on the shaft of your large gear.

If I slice the gears with Simplify3D and run the print 3 times, the ID of the small gear is 8.25 or 8.3mm (at or slightly under the model size) when measured with a set of digital calipers. The OD of the large gear shaft measures 7.85 or 7.9 (at or slightly over sized).

The diameter gap could range from 0.45mm to 0.35mm. But, I've had better luck with round parts if I think about the radius. That difference is 0.225mm to 0.175mm, which seem reasonable for a press fit. These parts come out nice and tight.

When I slice and print with PrusaSlic3r, the small gear comes out pretty similar at 8.3mm - 8.35mm (at or slightly over nominal). But, the shaft on the large gear is way under nominal at 7.65mm to 7.7mm. Neither the bearing or small gear really fit at all.

The PrusaSlic3r small gears all fit acceptable on the Simplify3D large gear shafts.

I have verified that I am using the latest version of PrusaSlic3r with all default settings.

For now, I will post a large gear with an oversize shaft.

I am open to suggestions if anyone has any....

Using different slicer can be reason for different experience with fit of the parts. For me none of the connection is really tight but the small gear is critical because it can fall off and the spool stops rewinding at all. I helped myself with some small pieces of filament making all connection tight.
I have read in some discussion that regardless the Extrussion multiplier seting in Slic3r PE or Prusaslicer there is "M221 S95" command in every gcode file from these slicers as some compensation. This can explain different results of prints from Simplify3D and Prusaslicer.

I just printed this and I like it very much. Very simple and printer-friendly design. Thanks. If I can make my suggestion, the 90mm version may spread apart after some use (change of spools) if you print it wih few walls. I'd make a wide circular notch on the bearing inserts (and corrisponding recesses on the stand) to "lock" it in place when the spool is reinserted. Does it make sense?
I would probably do it myself but the source files are not included.
Besides, thanks for your work!

Your description is clear and it is a great suggestion.

I have updated the bearing insert to include an "anti-spread" flange and both stands to accommodate it.

spot on! thank you!

Does it make sound as the gear clicks by while it rolls?

No...it is completely silent except for the track is at full extension during a long single filament extrusion. At that point, it makes a clicking sound similar to what is shown in Martin’s video.

Thats a shame, printer is my office and it would drive me crazy :D

It looks like both the 65 and the 90 mm threaded shafts are the same. I could very easily be incorrect.

you are absolutely correct....That was a renaming/upload error on my part and has been fixed.