Lion Spool Holder (yes another one)
https://www.prusaprinters.org/prints/4806-lion-spool-holder
Hi guys,
I realize everyone and their mother has tried their hand at this. I was dissatisfied with those I did try (but I did not try everyone's). And I hadn't seen a good weight based one yet (though I see now there are some good contenders). This version hopes to be exactly the minimum necessary to accomplish the goal of stopping print failures from happening because of your spool holder. It's been exceptionally better than anything else I've used and very easy to load.
So, besides my testimony, I'd like to give these points on why this sort of design is good:
- A weight gives a consistent constant force
- The mechanism can be made to never bind
- The holder itself has good leverage (for attaching to the spool) and is quick to load and unload
- This design has only simple parts that are easy to reprint or adjust as needed
I am also curious if people can tell me how to load the factory buffer with ease (though even after loading, it still sometimes failed to buffer the filament). But at this point, I'm satisfied with this solution (since the buffer still requires some sort of spool holder). Also, what are peoples experience with the "mini" buffer designs? Things like https://www.thingiverse.com/thing:3810577 seem like they should have slightly more cupping to ensure the filament realigns when loaded.
Overall, I want us to move forward and get the MMU working better. The filament loading has been a big source of errors for me (that is, the buffer or the spool holder binding in some way). I've spent a lot of time with the MMU and while it's not perfect, it does require the filament to not bind when loading and unloading. I hope that this design is helpful to others besides myself, either as a direct thing to print, or inspiration for even better solutions.
RE: Lion Spool Holder (yes another one)
Very nice design.
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Chuck H
3D Printer Review Blog
RE: Lion Spool Holder (yes another one)
Looks interesting. Would it be possible to post the stl files as well?
RE: Lion Spool Holder (yes another one)
(thank you Charles and Richard for your kind words).
Richard, the STL and STEP files are posted at https://www.prusaprinters.org/prints/4806-lion-spool-holder/files but if you need me to post them here I can try to do that as well.
RE: Lion Spool Holder (yes another one)
Excellent design. It would be great if it could be designed without the clicking noise though.
RE: Lion Spool Holder (yes another one)
I really like this concept, especially the ability to adjust the rewind force by changing the number of nuts on the rack.
RE: Lion Spool Holder (yes another one)
Excellent design. It would be great if it could be designed without the clicking noise though.
The video is maybe misleading, usually when it loads the weighted rack is in the lower position, and does not usually clack when loading. I had positioned it high so that you would see that binding does not occur even if that were to be the case. It does "clack" while printing, but only a few clacks a minute. I welcome suggestions.
RE: Lion Spool Holder (yes another one)
Very nicely done! The gravity powered rewinders are superior to the plastic spring tension ones, imo.
RE: Lion Spool Holder (yes another one)
If you could do a mod for wall mounting with bottom feed that would probably be the ideal design.
RE: Lion Spool Holder (yes another one)
Another suggestion: Use herringbone gears so the rack will self-center.
RE: Lion Spool Holder (yes another one)
Another suggestion: Use herringbone gears so the rack will self-center.
Hi Peter, I'm not familiar with herringbone's properties, right now I'm using standard involute gears, and they are only loosely coupled. This means that the spool and the rack both can move beyond their limit by decoupling (the rack is the only thing that typically does this, but it's important that the spool be able to, as a failure mode). My question then is, would a herringbone still allow this loose coupling?
Even so, I'm not sure if it's going to provide much of an advantage here, again because of the loose coupling. That is, if these were tightly coupled, then I could rely of on the herringbone profile to keep the rack constrained in one dimension (and could remove that constraint from the rack profile). But, if I did that then when the spool holder is not actually coupled with the rack, the rack loses that constraint, and then it would fall out! 🙂 I'm not sure if my words are as clear as a diagram, but I'm not a computer where I can provide one.
Thank you for bringing this up, I had only considered herringbone as a benefit for reducing gear backlash, I will at the least keep in mind that they can also be used for alignment in the future!
RE: Lion Spool Holder (yes another one)
Another suggestion: Use herringbone gears so the rack will self-center.
Hi Peter, I'm not familiar with herringbone's properties, right now I'm using standard involute gears, and they are only loosely coupled. This means that the spool and the rack both can move beyond their limit by decoupling (the rack is the only thing that typically does this, but it's important that the spool be able to, as a failure mode). My question then is, would a herringbone still allow this loose coupling?
Even so, I'm not sure if it's going to provide much of an advantage here, again because of the loose coupling. That is, if these were tightly coupled, then I could rely of on the herringbone profile to keep the rack constrained in one dimension (and could remove that constraint from the rack profile). But, if I did that then when the spool holder is not actually coupled with the rack, the rack loses that constraint, and then it would fall out! 🙂 I'm not sure if my words are as clear as a diagram, but I'm not a computer where I can provide one.
Thank you for bringing this up, I had only considered herringbone as a benefit for reducing gear backlash, I will at the least keep in mind that they can also be used for alignment in the future!
I think you could still loosely couple the gear at both ends with a herringbone gear. I'm not sure how much of an advantage self-centering really is, but I happen to think herringbone gears look cool 😀
RE: Lion Spool Holder (yes another one)
Hey @gryn, thanks for your post! Can you let us know which holders you've tried and what problems you had with it? Hopefully this will save some of us from wasting filament on something that ultimately may not work the way we want.
RE: Lion Spool Holder (yes another one)
Hey @gryn, thanks for your post! Can you let us know which holders you've tried and what problems you had with it? Hopefully this will save some of us from wasting filament on something that ultimately may not work the way we want.
The one I invested the heaviest into but was left disappointed was the spring based one posted here: https://www.thingiverse.com/thing:3338467
He has posted some revisions, but the clutch I don't feel will ever be reliable enough. He has adjusted some of the parts where they were too weak as well, so that is good too. Additionally, he has a gravity based one that is clever, since it uses the spool itself as the counter weight. I have not tried that one, as I didn't find it until after I had designed and tested the one posted above. I imagine it would perform well.
RE: Lion Spool Holder (yes another one)
Maybe print the weighted part out of a fairly stiff TPU?, as TPU has excellent wear resistance and the slight softness should reduce any clack noise, or maybe a last tooth clip in part from TPU, again, excellent wear resistance and a softer material so less noise.
Just ideas... 😀 Just not out of ninja flex, the result could be quite comical to see, but not really practical. 😜
Normal people believe that if it ain’t broke, don’t fix it. Engineers believe that if it ain’t broke, it doesn’t have enough features yet.
RE: Lion Spool Holder (yes another one)
Maybe print the weighted part out of a fairly stiff TPU?, as TPU has excellent wear resistance and the slight softness should reduce any clack noise, or maybe a last tooth clip in part from TPU, again, excellent wear resistance and a softer material so less noise.
Just ideas... 😀 Just not out of ninja flex, the result could be quite comical to see, but not really practical. 😜
Haha! Ninjaflex racks.
I haven't worked with these materials, certainly it might operate more quietly if the materials were softer than PLA. But I don't find it all that loud right now, I have 2 printers printing simultaneously, and you get a soft "clunk" sort of sound arrhythmically already. I probably should not have shot the video after all it seems, since it is making the impression that the tool goes "clack-clack-clack" as a normal use-case. 🙂 Overall, the MMU itself is much louder than the clunks from the spool holder.
*edit* after posting, I realized you might get a similar effect by simply removing the top and bottom walls from the rack and gear. This would allow the infill to flex more, which should reduce the sound more. You'd want to avoid cubic or other 3d infills. I could try that out sometime soon, it would at least be an easy and interesting experiment..
RE: Lion Spool Holder (yes another one)
@gryn
did you ever try my rewinder:
https://www.thingiverse.com/thing:3691892
or, it's drybox version?
https://www.thingiverse.com/thing:3842938
If you used them and had issues, I'd love to get the feedback.
RE: Lion Spool Holder (yes another one)
If you used them and had issues, I'd love to get the feedback.
Greg, those look lovely and I feel our designs are in the same family. But, I did not get to try yours out.
If I would give any feedback it would only be on the spool holder part, this is where we differ quite a bit. One thing I think would be helpful is if the pitch of the lever part of the spool holder was generally steep, I use something like 60 degrees, and I would estimate by eye that one of yours to be around 40 and the other 20? A steeper pitch here gives you better leverage to grip the spool (you're not *clamping* a cylinder you're trying to wedge your holder into the spool's shaft). Since, if you lose grip of the spool the rest of the mechanism is moot.
The second bit on the spool holder is I would also have a steeper pitch for the thread. This requires fewer turns to apply or remove the wedge from the spool. It is a trade off, though, because you lose your mechanical advantage for wedging into the spool (so it's a matter of taste if you want to have the last twist require a bit of force, or if you want it to be a breeze, but have to twist many more times).
If you do consider increasing the pitch, please notice how I did not thread the tip of the wedging piece so that I could reduce further how many twists I would need to apply wedge. (it allows the wedge to get further down the shaft before it needs to start twisting).
I want to also say, that after I had designed the Lion, I found yours and it was definitely the best candidate if I had not already finished my design. (i.e. Lion was good enough I did not feel like I needed to explore more). (This was also when I found the Sisyphus variant too, which may be okay, but I'm not sure if the added simplicity is a good or bad thing here, since now the force applied varies, and the rotational inertia built up may be problematic for a heavier spool -- though I guess I'd have to try it to find out). I think our two designs using a vertical weight keeps things simple and consistent. And yours using a gear may seem more complicated, but it's actually great for the dry box application.
BTW, I don't do much dry box printing, so when I do it's typically only one filament that needs it. So, I usually can get away with not having any rewinding because the friction in plug for the dry box keeps the filament from going back into the box (so I don't have to worry about the spool getting tangled), and since it's the only one without rewinding, it doesn't have much chance to cause tangles with everything else.
Thanks for pointing me towards your design, and thank you for making it!
RE: Lion Spool Holder (yes another one)
@gryn
They both operate on the principle of a counter-weighted vertical track. Even after having had a lot more time to think about it, I still believe this is the most effective mechanical mechanism.
The grip on the spool has never been an issue for me and I've not had any users express problems either. The inner and outer diameter on my nut and cap were driven by requests from users to support a very wide range of spool hub sizes. The differing slopes come from printer limitations. The nut is printed with the larger diameter down and can be thin with a steep slope. But, the cap has to be printed with the gears up in order to avoid supports. So, the slope from inner to outer diameter is an overhang and must therefore be a shallower angle.
Agree with you that thread pitch is a matter of preference. Martin Hoffman's circular track mechanism has a larger diameter custom coarse thread. At the time I designed mine, I went with a standard fine pitch thread on a smaller diameter shaft. Thingiverse user FlamenG later did a remix of my cap/shaft/nut with Martin's threads. Some of my rewinders are my original threads and some are FlamenG's. They both work great.
Your threads are definitely interesting and look like they would work well. I'll probably print a copy of your spool hub to see how it all goes together the next time my printer is idle.
The gear was really about rewind turns in my design. By having a gear ratio, I can have a fixed number of rewind turns using a shorter track with fewer teeth. I wanted to both be compact and to work with almost empty spools.
I've been working with another thingiverse user on TPU printing with theMMU2S, which led me to design the drybox version. I've started using the drybox all the time now as even my PLA was being affected my moisture more than I realized previously (live in very humid south Texas).
Your design looks very clean and functional to me and you are to be congratulated. I would encourage you to keep working on it and making any small improvements or refinements you discover along the way.
RE: Lion Spool Holder (yes another one)
@gryn
The gear was really about rewind turns in my design. By having a gear ratio, I can have a fixed number of rewind turns using a shorter track with fewer teeth. I wanted to both be compact and to work with almost empty spools.
I think the calculation I have on mine is about 1.5 revolutions, though what we are after is the retract length, and that unfortunately is driven by the spool's current diameter times the revolutions. (I.e. on a new spool 1.5 turns is quite a long ways, but on a nearly empty one, it's much less). However, on mostly empty spools there is often a high springiness in the filament (it has a lot of bend) so it neither wants to, or necessarily needs to be rewound as much as new spools where the filament behaves in a more "flat" way.
The only other thing I was worried about concerning the gear was if I was going to be able to provide enough force. When I designed this, I was out of town, so I had to guess at the amount of force needed to turn everything. It turns out to be around 100g (times g). With the gearing, you do have to multiply that number, but finding even 200g wouldn't be that hard, and you would get twice as much turns.