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Updated to Mark2 - Spool Holder for Prusa i3 MK2 - Hex Design - Toolless Mounting - Fast spool replacement

by MartinMajewski, published

Updated to Mark2 - Spool Holder for Prusa i3 MK2 - Hex Design - Toolless Mounting - Fast spool replacement by MartinMajewski Oct 22, 2016

Summary

Updated the project to "Mark2" - See project updates down below!


Original Text

Right after l got the Prusa i3 MK2 up and running, I noticed one major flaw of that otherwise fabulous machine:

The spool holder!

https://youtu.be/ovfynZAZd84

Not only that it looks not as well engineered as the other parts of the machine, but it is also not very convenient regarding usage. Especially if you want to do layer based color printing you have to switch the filament quite often during one print. Bending the original spool holder to release the mounted spool, as well as adjusting it to hold the new one in place (especially if the spools width differs from the first one) is time-consuming and tedious.

There are already a few alternatives here on Thingiverse, but after trying a few of them out, I found that they have some other issues.

  1. Their wheels are often mounted using printed hexagonal screws and nuts. This results in the need for tools like a wrench to tighten them up.

  2. The mounting to the metal frame of the Prusa i3 MK2 is often not well designed. Most of the alternative spool holders rely on pure force to clip the holders onto the frame. This has two consequences:

    1. The required force is not good for the printer's construction, nor the printed parts, that can easily break (as happen to some of the spool holder arms I printed).
    2. It makes adjustment for other spool widths very hard.

  3. If the extruder reaches a certain hight on the z-axis it could crash into the overhanging construction.
So I designed this spool holder, where the spool is laying on four wheels that roll smoothly on 608 (skater) bearings and hopefully eliminating the previous drawbacks. Speaking of which, ...

  • ... it is an all tool-less design. All parts are just slid into each other. The nuts can be tighten by hand.

  • ... the arm's clamping design is optimized for an easy attaching onto and detaching from the printers metal frame, with as little strain on the parts as possible. This makes also the width adjustment very unproblematic and fast.

  • ... due to the small footprint of the holder's arms, you can mount two spool holders side by side. The end of the idle filament thread can be locked placed into the hole of one of the axis' screws. This prevents the spool from uncoiling and tangling up.
Your opinion on this design and suggestions to make it even better is appreciated
Please also take a look at my other designs, printer parts and tools.

If you like to support me and my work, please consider to follow me

Sending a tip over Thingiverse will buy me some coffee to stay productive. :-)

Thank you very much.

Print Settings

Printer:

Prusa i3 MK2

Rafts:

No

Supports:

No

Resolution:

0.2 mm

Infill:

10% for all small parts, 20% for the arm.


Notes:

Note for Mark2: Please read the update information down below!

Original Text

To make the spool holder work, you need four 608 bearings for one set, which you can get from a local skater shop or from Amazon (by using the provided links you can support me and my work):

You often find eight bearings inside a set, which is enough for two spool holders.

The spool holder is designed in a way, that you can use all parts of both sides of the holder and also switch the axis screws from back to front and vice versa. If you like to have the "smooth bed side" oriented to the outside, you have to mirror the right arm along the x-axis.

For the infill, I used a honeycomb pattern because it matches the hexagonal style of the holder and my filament is quite translucent. Honeycomb gives good mechanical support in general.

I printed with three perimeters for all small. Four parameters were used for the arm and six perimeters for the wheels to avoid infill there. Each part has four top and bottom layers on my prints.

Even tough I printed my final design in 200µm (0.2 mm) layer resolution, I also tested 100um (0.1 mm) for the wheels. That gave them a smooth finish, but it had no effect on the mechanical properties.

Post-Printing

Screws and nuts...

Note for Mark2

Now there is more clearance between the threads of the screw and the nut. Therefore, you should be fine even without PTFE grease.

Original Note

The screws and nuts should fit nicely with small clearance. Nevertheless, it can be hard to get the nuts screwed onto the screws the first time. So give them a gentle press and try to find the sweet spot there the threads match up.

I also used a small amount of PTFE grease on the threads to make handling even easier.
You can find it e.g. on Amazon. Here are some affiliate links that you can use if you like to support me and my work:

Finish Line Fett Synthetik Casual Grease:

Bearing assembly

Note (especially for Mark2)

Print one single wheel/tire first! Then check, if you can press in the bearing. Bearings and wheels will always come with variances. What works for me, might not necessarily work for you. If you have a hard time to press fit the bearing (I mean a really, really hard time - I took the back of my screwdriver to press them in) into the tire, scale the tire up by a tiny amount (something of 0.01%) and try again.
I've printed the tires with 0.1 mm layer height for best results!

Original Note

The wheels are modeled with a small clearance. Therefore it is no always easy to press the 608 bearings into them. But here is how you will succeed:

  1. The wheel has a wider side. This side is oriented towards the holder's arm. Lay the wheel with the larger side flat on a table.

  2. Place the bearing onto the wheel. Try to push the bearing slightly into the wheel. It is enough if the bearing just barely sticks.

  3. Flip the wheel with the bearing around and press with your hand hard on the wheel's wider side. The bearing should pop in and be level with the wheel"s narrower side.

  4. Place the pressing-helper tool, that I provided as STL, onto the bearing and flip the wheel again, so that the pressing helper rests on the table. Now you can push again hard onto the wheel, and the bearing should pop completely into the wheel.

The pressing helper tool has a smaller diameter than the wheel"s inside diameter and should, therefore, be easy to remove.

Asymmetric Wheels

Note for Mark2

With the Mark2 the wheels become symmetrical. However, there is still an entrance side for the bearings, but it should not affect functionality if you put the wheels in reverse onto the axis.

Original Note

Be aware that the wheels are asymmetrical. They have a wider side regarding diameter. This larger side should be oriented towards the arms.

How I Designed This

Fusion 360

This spool holder was designed in Autodesk Fusion 360 and optimised to be printed on an Original Prusa i3 MK2.

Updates

Update to Mark2

The Mark2 implements all the suggestions from you, the users, as well as improvements I made during the usage of the first version.

Main differences are:

  • Wider arms: The arms are 10mm now in width, compared to the 5mm of the first version. This makes the whole assembly sit more stable at the frame. Furthermore, less infill and fewer perimeters are needed. As you can see I printed mine with a honeycomb infill without any top and bottom infill layers.
  • Larger distance between the wheels: I increased the distance between the front and rear wheel to let the spool slide a little bit deeper into the holder. This modification makes the run smoother and holds the spool in place more securely.
  • Lower center of mass: The arms are now smaller in height relating to the printer's metal frame. This removes some leverage forces from the frame. I designed it carefully so that you can still go all the way up with the extruder carriage without jamming against the holders.
  • Asymmetric arms: There is sadly no one-fits-all solution. With the Mark2, asymmetric arms are introduced to make the axis screws snap-in flush with the arm's outer side. With this change, two arms can now be mounted directly next to each other without any gap. And it looks better IMHO.
  • Symmetric wheels: As the asymmetry of the first version's wheel did not provide any benefits, I scrapped this design. The current wheels / tires center the spool more efficiently and have a cleaner look (print them with 0.1mm layer height for a smooth ride!).
  • Wider cable holes: The hex-cable hole is now 16mm wide, compared to the 15.43mm of version 1. This should allow more cable connectors to fit through.
  • Wider Nut: The nut is now a lot wider and has more grip for a better tool-less mounting experience.
  • Better threads: Lessens learned on how to design threads. The Mark2 threads on the screw and nut fit better now. PTFE grease should not be necessary with the Mark2.

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This is the first upgrade I really think is worthwhile for my almost perfect Original Prusa. I printed all in black and everything fits perfect. The bearing just fit tight as should with no tweaking in scale. I printed some small parts with the new spool holder and worked like a charm.

So I left home with a 5 hour long print running and when I came back I noted that something went wrong. I realized the filament brand I bought here in Brazil (imported God knows from where) came full almost where the filament almost escape from the border of the spool.
So one turn escaped and get trapped in the nuts and halted the filament cutting extrusion. I put the same print over again and watched carefully and another turn escaped from the spool and get trapped over again. So I get an old filament guide from my Anet A8 and improvised to keep the filament aligned in the middle of the printer frame. Put the same file to print and now went without problems. I don´t know if anybody also had this problem since the spool must be really full at the limit. Sure after some prints the spool will empty a little and this problem never will happen again.

As a suggestion, if some more users bump in this very same problem, wold be a nice touch add a filament guide integrated in the system. As curiosity, I don´t know if this could imply in problems, but the screws could be integrated in the arm in order to be just one print for this three parts?

All in all just an ingenious design and I loving it. Thank you for sharing.

Hi,

That is an interesting and not pleasant issue, for sure. However, you are the first person reporting it. Sure, the filament can slip off of the borders of the spool. That happens to me also on other spool holders, but mostly due to not paying enough attention while changing the filament and letting the filament losing tension while it slips through my fingers. However, I had never observed it during print. One user reported that the entire spool came off of the holder, but he figured out that the filament was massively tangled and the extruder kept pulling it.

I encourage every user to report this kind of issues because it is the only way to improve the design to be more and more failproof. With the Mark 2, the spool sits lower in the holder, with the wheels grabbing it more from the sides. This should minimize the issue of the mentioned user a bit.

Therefore, also a big thank you for reporting your issue.

A filament guide is on its way, but currently, I have no time to finalize it. However, there are plenty of them on Thingiverse. Nevertheless, you will also encounter problems with filament guides on high extruder positions, because the curvature of the filament is beyond good then. So search for a guide that gives the filament room the flex while the extruder prints at 150 mm and above.

I have designed the spool holders in separate parts because of several reasons. The first version has symmetrical arms so that you could print and use one arm for both sides. This would not be the case with integrated screws. Second, some users have no issues printing the arms but need several trials to print the screws because of calibration and tolerances. Separating the screws from the arms makes this attempts faster to print, and you don't have to throw away so much plastic. And lastly, with the screws separated you can print them in different colors or even materials, which gives greater freedom for creativity.

However, you can combine all parts to one print with nearly every slicing program. I know, this is more work, than using a single STL file, but that is the current status. Maybe I will provide a combined version in the future. But as I said, I have currently not the spare time at hand.

Thank you for your feedback and happy printing! :-)

Martin

4 days ago - Modified 4 days ago
gandara - in reply to MartinMajewski

Bear in mind that this issue only happened because my spool was full beyond the normal. Certainly after use about 8mm (in the diameter of the filament in the spool) this will be no issue.

I found a filament guide suitable for high prints and is already installed. But now I will only be sure of the efficiency when I open a brand new spool. I will let you know.

I suspected that you would have a good reason, but those were a smoking gun.

Once again, congratulations this amazing design.

I printed the MK2 versions for my new Prusa i3 mk2 printer. I really like how these turned out! The fit is very snug with the bolts in the frame, but the nuts screw onto the bolts smoothly and with barely any effort. Very well designed! The brackets themselves fit tightly to the metal frame of my Prusa i3 mk2, with no wobble or looseness at all. It may loosen over time, as I have to move them based on different spool widths, but I doubt it will be by much. The only item that caused me some slight concern is how tight the fit is for the bearings inside the wheels. I had to use a metal punch and tap them into place with a hammer to get them in as far as intended. I'm certain that it would take the same to remove them later. But that's something that can be adjusted by sizing the part before printing, not a concern of the design itself. These were the third things I've printed after assembling my printer from the kit, so I just used all of the defaults it came with. Printed beautifully! The only thing that might be nice would be a hole to store the filament end when not using the spool, like in the first design. But that's easy enough to add with a drill bit too ;). Awesome work Martin!

Thank you very much for your fantastic feedback and the tip you've sent! I will put it to good use and am very happy that you like the holders.

As I already mentioned in the project's description, there seem to be tolerances with the bearings, and they should be scaled (or hammered! g) to fit. With the first design users reported that the wheels were too big.

Regarding the filament hole: The hole inside the screw's end of the first design was too small if you've just unloaded it from the extruder, because of the blob on the end of the filament's wire. So cutting the thread first to get the filament into the hole was a troubling step if you were in a hurry.
So I decided to scrap the idea. But: if you print the nuts with no bottom layer and a suited infill pattern, you can have very nice filament holes! :-D Just look at the Mark 2 picture. You can also set the top most layer of the screw to zero to get the same result as with the first model.

Have a nice day and happy printing!
Martin

Will this work with the anet a8?

Sorry friend, I have no idea. I do not have an anet a8 nor is this spool holder designed for it. If your printer's frame has the same dimensions as the ones provided in the technical drawings than it probably will work. Otherwise, you have to do a remix by yourself.

Happy printing.
Martin

Feb 8, 2017 - Modified Feb 8, 2017

Any advantage to upgrading to the Mk2 screws/nuts?

Additionally, I wish you'd snug up the print dimensions a bit in regards to where it clips onto the frame. Mine still fits rather sloppy.

Love the design though! Using it on both of my Prusa MK2 printers.

The MK2 screws and nuts are designed to work with the 10mm wide arm. You can try to use the old nuts if you like, but with the MK2 versions you don't need a spacer between arm and bearing anymore, and the threads are a lot better now. Print time for four screws and four nuts was about 2,5 hours for me.

Regarding the dimensions: I am not sure, why your results are that sloppy, nor do I see how sloppy it is. You will not get a totally perfect and stiff experience with an FFF 3D-printed part, that's for sure, because not every layer equals the other. Furthermore, a perfect fit would require a perfect 90-degree cornering, which is not achievable with molten plastic.

But it should not wiggle more than 10 mm at the rear end - at most. If you look at the technical drawing at the project's update section, you will notice, that the arm has now no clearance to the frame at all. More "snug" and you will have to cut-of parts. I would suggest that you tune your print setting a little bit. Maybe a wider extrusion width on the perimeters will remove your clearance between the arm and frame. The other possibility is, that you are underextruding a little bit. But I cannot judge without more information, like pictures or a video clip.

Have a nice day.

Love your design, however, the image posted with the honey-comb internal structure arms are not posted in the thing files. Is that a feature that was was removed in the final?

No. This is just a print setting you have to set inside your slicing application.

In slic3r you simply set 0 for the solid infill shells at the top and the bottom. Then slic3r will print the internal infill on all layers. In my case, I simply printed with the honeycomb infill pattern at 20% throughout the entire structure.

You can, however, choose whatever infill pattern you like most, or you print it traditionally with a solid top and bottom layer.

Hope that helps.

that's a nifty trick!

Ahh, makes sense. Thanks! I printed it in PLA, and it fits perfectly on the frame without having to reduce or increase the scale. Getting the bearings in the mail today.

Best,
David

Thank you very much, such an improvement to my Prusa. My TPU prints works alot better using this holder as well!

You're welcome! Happy printing!

Which hexarm is the latest revision? There's three in the files, and nothing specific as to which is the older/newer.

Seriously, Thingiverse should fix project's management tools. Anyway, the "Mark 2" files should be gone by now.

Sorry for the inconvenience. Thingiverse has some bugs in the project management console. The other to files were actually early prototype versions of the Holder's successor "Mark 2". I was about to release it but found some issues with the design and therefore never intentionally saved them here. :-P

Jan 21, 2017 - Modified Jan 23, 2017
  • Do you guys print it in PLA or ABS? Is PLA strong enough?
  • I guess it would additionally make sense to print the wheels with some kind of flex material? NinjaFlex?

Update: Printed all parts in PLA. Everything is perfect but it would be great to have the wheels in NinjaFlex.

Jan 16, 2017 - Modified Jan 16, 2017

Martin do you think you could invite me to your project for this make in Fusion? I would like to modify the fit just a little before printing to fit my Anet 8 frame width. My name is the same on Fusion; mrjoeyman. Real name Joel West

Hi Joel,

I'm really sorry, but as I also use parts of the design for my professional work, I am not allowed to open the raw project files for public use. The CC license only applies to the exported STL / polygonal files.

But as you're also using Fusion 360 it should be no problem to import the STL file and redraw the outlines of the arms into a new sketch. In fact I have also provided a picture of the technical drawing of the arms' mounting segment here. This should not take long, as the arms are really a simple design.

You can also take a look at the remix section of this project. I think I saw an Anet 8 modification being there already.

Have a nice week,
Martin

Thanks bud!

I like the idea and it helped me to print from a 2kg spool that does not fit on my current spool holder. So far so good. On the other even with an 1kg spool the construction is not very stable. Of course it works nicely when you don't touch it but I'm afraid the the spool will fall down when I touch it. I think a solution could be to make the arms a little thicker, so that the back cannot swing anymore.

I use it with 1kg spools 24/7, I switch spools for Multi-Color-Printing and two printers are "rocking" the table constantly. Never lost a spool with these holders. As soon as a spool is sitting on the wheels it is rock solid on my machines. One way to make it sturdier is to print another arm and connect two arms with a printed screw. If you are using the two spools configuration, you will get the stabilisation effect automatically.

However, If you want it thicker by itself, check out the derivate section. One other user has already made a sturdier version. You can also increase the scale on the proper axis during slicing. :-)

Happy printing.

Jan 2, 2017 - Modified Jan 2, 2017

Very nice design! I'm printing one up right now on my M2 while waiting on my Prusa to arrive -- maybe next week.

Anyway - in general, I find it very handy to have a tap-and-die set on hand if you're printing any object with standard threads. You can pick up a cheap import set since you'll probably only use them on plastic. A easy pass of the nuts and bolts in this model through the M8 x 1.25 die and tap cleaned up the threads very quickly - now they work and feel like machined parts.

I am a bit concerned with beam-mounted spool holders in general, wondering if, perhaps, the mass that high might contribute to a subtle swaying of the z-axis. I understand the frame is pretty sturdy, but... I'll probably feel better about it when I have the printer in my hands.

In the past, I've always preferred table-mounted spool holders with a reverse-bowden setup. I'll see what I can find on thingiverse before working on my own. In the meantime, I like your design and I know I'll enjoy using it. Thanks!

You're welcome! I am happy that you like it.

I like the frame mounting, because it saves me a lot of desktop space. But you're right, having as less stress on the construction as possible is always better. That's why many people are reporting to notice less printing artifacts using my design, than as they were using the original Prusa made holder. The smooth rotation and the lowered tension benefit the print quality.

I have also thought of making a table top spool holder, but due to several other circumstances I had no time to pursue this idea. Meanwhile there is a remix of my holder, that accomplishes exactly that: http://www.thingiverse.com/thing:1940365

Please share your made spool holder with us and link it as "Made" to this project. Thanks.

Happy new year and best wishes,
Martin

Desk Spool Holder

Hello Martin. Nicely done Spool Holder. I printed Spool Holder Spacers twice (4 pairs) for 1 holder and also 3 pieces braces. Spacers are on left and right sides bearings to avoid tight rotation. Braces are for strong construction due to width spool which I am using. I am testing this construction for while. Finally wil be glued to spool holder.

Hi,

Thank you for your compliment.
Please report back how your print went out.

Thanks and happy new year!
Martin

Dec 3, 2016 - Modified Dec 3, 2016

This is an awesome design! Highly functional, easy to assemble but still esthetic. I love it.

The Z-artifacts in my prints disappeared since I'm using this holder! The extruder simply had to pull too hard (and unevenly) with the original design.

Right now I'm reprinting the rolls at 99% since at 100% they are a bit loose on the bearings. Will upload a make as soon as finished.

Edit: Okay, at 99% they are way too tight, I keep the loose ones...

One suggestion for your design: I think the thread on the bolt should be one millimeter (or maybe a half millimeter) longer. When screwing on the nut it's running out of thread at the end.

Hi,

first off, thank you for your compliment.

3D-printing of objects here from Thingiverse is always a matter of trial and error, since no two printers do the exact same job with the exact same precision. For most people printing this holder on a Prusa i3 MK2 the 100% scaling and all parts seems to work.
Maybe your bearings are somewhat on wrong side of a production tolerance. Mine are sitting very tight, as you can see on the video. That's why I have provided the pressing helper. As I said: it is hard to make a one-fits-all object. I hope you have found the right scaling by now.

I will look into the "running out of thread" issue as soon as I get the time for this. Thank you.

Please share your made spool holder with us as linked "Made" project here on Thingiverse.

Happy new year and best wishes,
Martin

im on the way to remake this for my Wanhao i3 plus. will upload a remix when im done testing. your design is simple yet perfect. thank u =) will update with pictures later =)

Cool! I'm glad to hear that you like it. Please link your remake to my project. Happy making.

they are in the printer now if they work i´ll upload them. and of course i will post them as a remake of yours =)

Today I did my first print after installing this. There is a big difference in the quality of the print, especially close up. I think my extruder was struggling to pull the filament off the spool. A highly recommended upgrade.

Thank you very much for expressing your appreciation. :-)

Well, I mean printing anything on my beautiful Prusa MK2 is just great, however This is truly a great design and a pleasure to make and utilize and appreciate so much...Many thanks..and Great Work. I even went out and bought PIG wheels at the local skate shop..The design is worth the respect brother...:)

Thank you so much for this compliment! ;-)

I got the 8 pack of bearings from amazon.com, printed these up, and they work great! A vast improvement for filament swapping and operation overall. Thanks for the time and the great design.

You're welcome! Glad I could help. :-)

Comments deleted.

This is awesome, any chance I can convince you to share your step files? I'm working on a similar design, and much of what you've got here would work for me.

I have to think about it (and maybe clean up my Fusion project for it^^). Please contact me via mail (at) martinmajewski.net and share some information regarding your design. Maybe we can collaborate somehow. :-)

Oct 23, 2016 - Modified Oct 23, 2016

How comes these gadgets are in 3D printer parts and not accessories or even "art" ? Not one day without yet an other cable attachment, spool, switch, filament, "sensor" ... holder/guide that anyone can make in the blink of an eye with about anything. All these gimmicks clutter the REAL parts eventually bringing REAL and useful ideas ?

BTW, even ig this spool holder is one step above the usual we can find here, I think it is not wise to put such mass being jerked by the extruder on top of not very rigid frames !

Oct 23, 2016 - Modified Oct 23, 2016
MartinMajewski - in reply to MKSA

Hi and thank you very much for your opinion. I really appreciate it.

Mine is, that these "gadgets" are not accessories, because they fulfil a practical task on a printer and can greatly enhance the quality or usability of a printer. They are either not art, because they follow strict mechanical or structural rules and measurements. So design follows function and therefore there is really nothing to be called "art".

I don't know if you have any experience with the Original Prusa i3 MK2, but the frame is not flimsy (anymore). I achieve very detailed, precise and reliable 3D prints even with this "mass" on top. In fact Prusa Research puts the spools on this "flimsy" frame themselves as by design. They do not restrict neither the weight of the spools the user can put on top, nor the width of them. So you can theoretically put a 4 kg spool at the original spool holder (even though i doubt that the original design will handle them mechanically). Furthermore, my holder is not very heavy at all, so it does not contribute very much to the overall weight. I personally think, that the smoother spool unwinding even decreases the stress that the extruder puts on the frame while pulling on the filament. The other advantage is, that the user can change spools without putting any force to the frame, as they inevitably do with the original design by forcing the holder's arms apart.

But that is just my humble opinion. :-)

But you are right with the category hint. As soon as I design some decorations for the printer, I will put them either in one of your suggested places.

So long, have a nice Sunday evening and a superb new week.

Bye

Thinkverse should then have categories for "spool holder" "filament guide" "fan duct" "switch holder" ...

Now, should you come with a real novel implementation like a motorized spool holder that would deliver automatically the filament to reduce the pull required by the extruder/hot end carriage, give a shout.

I will! :-)

Thank you very much for your suggestion.

Excellent design. Downloaded!

Thank you very much! :-)

Please share your printed version with us in the "Made" section.

If you encounter any problems with my design or the provided information, or if you have any improvement suggestions, please let me know.

Happy making!

Yes, for sure. Just have to get the bearings.

I made some spool reductions for original Prusa spool holder meanwhile. Check my things. :-)

That perfectly spooled filament tho

What do you mean by that?

The black filament in the photo is spooled very nicely.

Yeah, Material 4 Print makes really nicely spooled Filament... At least at the last third of the spool! ;-)

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