Prusa XL spool holder

I made this mount to make a much more stable, and reliable, way to mount my spools on the Prusa XL. Yes, it's a little more work (+30s) to mount and remove the spools, but they will now rotate perfectly aligned, and with no vertical or horizontal movements or instability.

I have tested this with 4-5 different brand of filament, which is what I have at hands. In theory this should work for most if not all 1KG rolls, but would love to hear more what works and what doesn't.

Versions

Important! It's come to my attention that there are two spool versions shipped with the Prusa XL. My initial version was for the M4x12mm screw, but there's a “Version A” which has a different screw.

• Version B: This is the default, for the M4x12mm screw and attachment. Unless otherwise specified, the .step files and the .3mf file is for this version.
• Version A: This is the model with the longer M5x85mm bolt. The .step files and .3mf files are clearly indicated for this variant.

Note that it's only the two bolt halves that changes here, everything else is the same.

In addition, there's a “Long” variant of the entire assembly, which would possibly be useful for the 2KG and bigger spools.

Updates

• 01-31-2025: I added a longer version of the holder screw. This makes it possible to use the short mount with a 2KG (or maybe bigger) spool, even with the short bolts. I'd recommend this over the longer bolt that is available.
• 02-29-2024: Added the Version A variant of the bolt.
• 02-28-2024: I improved the threads on the big (hex shaped) nut. This makes a tighter hold, but requires reprinting the entire holder (but not the other big nut it stays the same.
• 02-26-2024: I modified the bolt slightly, to make the joint a little bit stronger.
• 02-26-2024: I added a folder with 4 optional parts to print a very wide spool holder. This would theoretically be for e.g. 2KG spools. Now, I haven't tested this, and I fear it may be very difficult to mount this on the frame since it will need a very long tool. But, if anyone is trying this, let me know if this is just too long and if we can make it shorter for tools to actually reach the screw as needed.

Parts

There are a few fundamental parts here, which my arbitrary naming convention:

• The bolt: This is the inner mount, that gets mounted to the Prusa XL frame, using an M4x12mm screw. This also functions as the inner ring of the semi-bearing for this design.
• The Holder: This is the holder for the actual spool. Most of this is permanently mounted with the bolt above, on the XL frame. But there is one part that is free, which is used to firmly attach the spool (of almost any size) to the holder. The inside of the holder is referred to as “The Tube”. There's now also a longer variant of the holder screw, which works very well for larger (2KG) spools.
• The Tool: This is an optional tool to hold the frame mounted holder while attaching the spool and spool screw. I'm saying this is optional, because so far, I've been able to easily hold the frame mounted holder with my hand while attaching and removing the spools.

Printing

There are three .3mf files here, for the Prusa XL. Two plate for the bolt and holder, and a third plate for the optional wide (long) spool holder. My preferred way of printing this is with The Bolt in one color (black), and The Holder in whatever colors I fancy. You are free to do whatever.

I've only printed this in Prusament PETG but I imagine PLA or ASA ought to work well. The way I place the half tubes on the plate allows for very strong layers that should resist a lot of force. My .3mf files do use supports for these parts, it's the only way I've tested it, but in theory the bridging may be ok. However, using say PLA for the support interface works incredibly well, but does require at least 2 tools to print. The 3mf files uses interface supports.

Assembly

After printing all the parts, start by combining the bolt with the plate nut and the bolt nut. The plate nut must go on the inside portion of the bolt, which is also the part with the shortest threaded part. The bolt nut goes on the outwards facing part, and obviously goes on the longest of the two threaded parts of the bolt. Both should be tightened as hard as you can. I don't think any of them need glue.

The next step is optional: I put a bit of super lube inside the holder's bearing joints:

Then place the bolt inside one of the two holder parts. Make sure that the side with the nut plate (for the frame mount) is on the side of the holder with the fine threads. In the picture above, that is the left side of the yellow parts. In the above, the black bolt goes into the yellow holder just as it's laid out.

Now combine the two holder parts, and using the holder lock (the screw with the hex shape) combine the parts. The holder locks goes on the left side of this, and should slide over the plate nut easily. Finally, attach the ring to the right side, which now is permanently holding the right side together. Both the holder lock and the small ring should be tightened firmly.

The last part, the holder screw, should easily move on and off the mount. The final assembly should look like this:

Mounting to the XL frame

Now with all parts combined, you just have to mount this on the frame. Remove the old spool holder (if any), and using the M4x12 screw, using a long allen / hex tool, attach the bolt on the frame. This can be a little tricky, you will need to put the M4 screw on the allen tool, and carefully thread it thorough the bolt until it sticks out behind the plate nut. Then using the alignment tab on the plate nut, attach the entire assembly tightly to the frame.

The holder part (yellow in the above) should now easily rotate around the bolt. If it doesn't, something has gone wrong…

Feedback

Finally, this is still experimental, and I'm definitely looking for feedback and comments as to what works, and doesn't work.