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  1. Please prepare tools for this chapter:
    • Please prepare tools for this chapter:

    • 2.5mm Allen key for M3 screws

  2. This guide is describing an assembly of a single spool holder. Your package should include 5, simply repeat all the steps again until you finish all spool holders.
    • This guide is describing an assembly of a single spool holder. Your package should include 5, simply repeat all the steps again until you finish all spool holders.

    • Take the black plastic spool holder base and turn it upside down.

    • Using cloth + detergent or IPA clean all four corners from dust and grease.

    • Let the surface fully dry and proceed to the next step.

  3. For each spool holder base prepare 4 foam pads. Peel off the yellow protective film completely. Stick the foam pad on the bottom of the spool holder base and hold it for a while. DON'T use too much force, you might deform the plastic shell.
    • For each spool holder base prepare 4 foam pads.

    • Peel off the yellow protective film completely.

    • Stick the foam pad on the bottom of the spool holder base and hold it for a while. DON'T use too much force, you might deform the plastic shell.

    • The foam pads are important to increase contact between the spool holder base and the surface underneath and reduce the spool holder from moving.

  4. Let's assemble the shafts holding the spools, you will need: Bearings (4x)
    • Let's assemble the shafts holding the spools, you will need:

    • Bearings (4x)

    • Shaft (2x)

    • Shafts can be black or silver, the dimensions are the same.

  5. Align the bearing with the end of the shaft. Assemble bearings on both sides of the shaft.
    • Align the bearing with the end of the shaft.

    • Assemble bearings on both sides of the shaft.

    • The rubber seals next to the bearing were used for the purpose of the photography, no need to use them.

  6. For the following steps, please prepare: spool holder base (1x)
    • For the following steps, please prepare:

    • spool holder base (1x)

    • shaft with bearings (2x)

    • mmu2-s-holder-endstop (4x)

  7. Rotate the base with the cutout part towards you. Insert the shafts into the spool holder base. Make sure all four bearings are seated properly.
    • Rotate the base with the cutout part towards you.

    • Insert the shafts into the spool holder base. Make sure all four bearings are seated properly.

    • Insert the endstops in all four sockets. Push them all the way in, but make sure you won't deform the spool holder base.

    • Make sure the shafts can rotate freely.

  8. For the following steps, please prepare: M3x40 screw (10x)
    • For the following steps, please prepare:

    • M3x40 screw (10x)

    • M3x12 screw (10x)

    • M3n nut (10x)

    • Buffer plate (6x)

    • PTFE tube 4x2x150 mm (5x)

    • The list continues in the next step.

    • The Buffer plates are protected by a thin protective film, you can remove it now. Be careful during the assembly to avoid scratches.

  9. Open the bag with the plastic parts and look for the hooks. There are two versions:
    • Open the bag with the plastic parts and look for the hooks. There are two versions:

    • New version with a longer hook compatible with MK3S and MK2.5S. Please jump to the Step 10

    • Old version with a shorter hook compatible only with MK3S. Please jump to the Step 15

    • All printable parts are also available at prusa3d.com/prusa-i3-printable-parts

  10. s-buffer-printer (1x) s-buffer-spools (1x)
    • s-buffer-printer (1x)

    • s-buffer-spools (1x)

    • s-buffer-spacer (4x)

    • s-buffer-hook-uni (2x)

    • As the names suggest, there are parts, which will connect to the printer or to the spools.

    • IMPORTANT: the holes for the PTFE tubes have to match between both parts. See the picture. Make sure you won't flip them.

    • On one side you have 3 holes, same goes for the second printed part.

    • Other side has only 2 holes.

  11. Take the larger printed part (s-buffer-printer) and place it like in the picture with two holes facing to the right. Prepare something slightly heavy and tall (e.g. empty glass), we will use it in a second. Grab one plate and slide it in, it will fit in the slot.
    • Take the larger printed part (s-buffer-printer) and place it like in the picture with two holes facing to the right.

    • Prepare something slightly heavy and tall (e.g. empty glass), we will use it in a second.

    • Grab one plate and slide it in, it will fit in the slot.

    • Make sure the surface with previously removed protective film is facing towards you.

    • The entire assembly will have a tendency to fall over, use the prepared object to support it from behind.

    • Slide another 5 plates in the printed part. Make sure the surfaces with previously removed protective films are facing towards you.

    • Use two M3x40 screws and push them through the printed part. Ensure the screws are all the way through.

    • Don't turn the Buffer yet.

  12. Arrange the plates on top of the  Buffer and slide in the second printed part (s-buffer-spools). Make sure the side with two holes is on the right. Seat the printed part on the other side as well.
    • Arrange the plates on top of the Buffer and slide in the second printed part (s-buffer-spools).

    • Make sure the side with two holes is on the right.

    • Seat the printed part on the other side as well.

    • Secure the printed part using two screws M3x40.

    • Don't turn the Buffer yet.

  13. Now turn the Buffer and place four nuts on the screws. Before you start tightening, please read the following instructions: DON'T TIGHTEN the screws too firmly. You will deform the plates and the Buffer might not work properly. Make sure the plates are parallel and not bent. It is enough just to catch the nut (use its entire internal thread).
    • Now turn the Buffer and place four nuts on the screws. Before you start tightening, please read the following instructions:

    • DON'T TIGHTEN the screws too firmly. You will deform the plates and the Buffer might not work properly. Make sure the plates are parallel and not bent.

    • It is enough just to catch the nut (use its entire internal thread).

    • Use this approach on all parts, which are holding the plates.

  14. Turn the Buffer back, two holes are facing to the right again. Take three s-buffer-spacer parts and place them on the side with two holes. Secure each s-buffer-spacer with a M3x40 screw.
    • Turn the Buffer back, two holes are facing to the right again.

    • Take three s-buffer-spacer parts and place them on the side with two holes.

    • Secure each s-buffer-spacer with a M3x40 screw.

    • Take two s-buffer-hook-uni parts and place them on the other side. This position of hooks is compatible both with MK3S and MK2.5S, but you can rearrange it.

    • Take the last s-buffer-spacer and place it to the corner.

    • Secure each printer part with a M3x40 screw.

    • Use six M3n nuts from the other side and tighten the screws. Keep in mind the proper tightening. Avoid deforming the plates!

    • Now, skip to the Step 20.

  15. s-buffer-spacer (3x) s-buffer-spacer-hook (3x)
    • s-buffer-spacer (3x)

    • s-buffer-spacer-hook (3x)

    • s-buffer-printer (1x)

    • s-buffer-spools (1x)

    • As the names suggest, there are parts, which will connect to the printer or to the spools.

    • IMPORTANT: the holes for the PTFE tubes have to match between both parts. See the picture. Make sure you won't flip them.

    • On one side you have 3 holes, same goes for the second printed part.

    • Other side has only 2 holes.

  16. Take the larger printed part (s-buffer-printer) and place it like in the picture with two holes facing to the right. Prepare something slightly heavy and tall (e.g. empty glass), we will use it in a second. Grab one plate and slide it in, it will fit in the slot.
    • Take the larger printed part (s-buffer-printer) and place it like in the picture with two holes facing to the right.

    • Prepare something slightly heavy and tall (e.g. empty glass), we will use it in a second.

    • Grab one plate and slide it in, it will fit in the slot.

    • Make sure the surface with removed protective film is facing towards you.

    • The entire assembly will have a tendency to fall over, use the prepared object to support it from behind.

    • Slide another 5 plates in the printed part. Make sure the surface with removed protective film is facing towards you.

    • Use two M3x40 screws and push them through the printed part. Ensure the screws are all the way through.

    • Don't turn the Buffer yet.

  17. Arrange the plates on top of the  Buffer and slide in the second printed part (s-buffer-spools). Make sure the side with two holes is on the right. Seat the printed part on the other side as well.
    • Arrange the plates on top of the Buffer and slide in the second printed part (s-buffer-spools).

    • Make sure the side with two holes is on the right.

    • Seat the printed part on the other side as well.

    • Secure the printed part using two screws M3x40.

    • Don't turn the Buffer yet.

  18. Now turn the Buffer and place four nuts on the screws. Before you start tightening, please read the following instructions: DON'T TIGHTEN the screws too firmly. You will deform the plates and the Buffer might not work properly. Make sure the plates are parallel and not bent. It is enough just to catch the nut (use its entire internal thread).
    • Now turn the Buffer and place four nuts on the screws. Before you start tightening, please read the following instructions:

    • DON'T TIGHTEN the screws too firmly. You will deform the plates and the Buffer might not work properly. Make sure the plates are parallel and not bent.

    • It is enough just to catch the nut (use its entire internal thread).

    • Use this approach on all parts, which are holding the plates.

  19. Turn the Buffer back, two holes are facing to the right again. Take three s-buffer-spacer parts and place them on the side with two holes. Secure each s-buffer-spacer with a M3x40 screw.
    • Turn the Buffer back, two holes are facing to the right again.

    • Take three s-buffer-spacer parts and place them on the side with two holes.

    • Secure each s-buffer-spacer with a M3x40 screw.

    • Take three s-buffer-spacer-hook parts and place them on the other side.

    • Secure each s-buffer-spacer-hook with a M3x40 screw.

    • Use six M3n nuts from the other side and tighten the screws. Keep in mind the proper tightening. Avoid deforming the plates!

  20. Take the 150mm PTFE tubes and slide them in to the smaller of the two printed parts. Make sure the PTFE tube sticks out on the other side (inside the Buffer) just 2-3 mm, not more. Secure the PTFE tubes using five M3x12 screws. You can tighten them slightly above the surface.
    • Take the 150mm PTFE tubes and slide them in to the smaller of the two printed parts. Make sure the PTFE tube sticks out on the other side (inside the Buffer) just 2-3 mm, not more.

    • Secure the PTFE tubes using five M3x12 screws. You can tighten them slightly above the surface.

    • CHECK EACH PTFE TUBE with a piece of filament to ensure it can move smoothly inside the tube. If not, release the screw a bit.

  21. That was easy, right?
    • That was easy, right?

    • Spool holders and Buffer are easy to make, research shows that 10 % is enough.

  22. Did you assemble all five spool holders and the Buffer? Do they look like those in the photo? Note that the hooks on the buffer will differ depending on your version.
    • Did you assemble all five spool holders and the Buffer?

    • Do they look like those in the photo? Note that the hooks on the buffer will differ depending on your version.

    • There are 5 screws (M3x12) remaining, keep them for connecting the printer tubes to the buffer, later while reading the Handbook.

    • Now, just a 8. Preflight check and the MMU2S is ready!

Finish Line

396 other people completed this guide.

Jakub Dolezal

Member since: 02/20/2017

222 Guides authored

Team

Prusa Research Member of Prusa Research

Community

3 Members

364 Guides authored

42 Comments

I’ve had a few days to play with the buffer now. It’s a neat idea, but trying to load filament is a nightmare. I look at picture 9 in the handbook and I laugh in frustration.

Filament spends its life on a spool and will naturally want to bend. I cannot get it from one side of the buffer to the other without curving out the side somewhere else. I can change the orientation of the spool before feeding, trying to take advantage of the bend. But it will just shoot out a different (and still wrong) spot in the buffer. There’s also only so much filament straightening I can do with my fingers.

The buffer would work if it narrowed on the inlet like it narrows at the outlet. If the buffer narrowed at the inlet, I could grab the filament as it enters the inlet ptfe tube and pass it through the buffer using something else I can control (a stick, a loose ptfe tube, etc). Once I get it to the other side, I can feed it into the outlet pfte tube.

Basically, if the buffer was symmetrical, I think we’d have a winner.

Jeff Gros - Reply

Dear Jeff,

Please rest assured we are thoroughly testing every product before we make it available to our customers. On our test farm, the buffer fulfills its purpose just fine. If you have an idea on how to improve it, feel free to modify the design and let us know how does it work :)

Martin L. - Official Prusa CS -

I haven’t found filament loading to be a “nightmare”, but it does take some effort. I seem to have been able to get better at it with a bit of practice. While it is harder than loading filament directly into the extruder, it isn’t going to be an impediment.

One thing that might help is if the laser-cut buffer plates were clear rather than black. That would allow you to see where the filament is headed so you could try twisting it or adjusting your approach.

Dean Reece -

Thanks Dean, your feedback has been noted.

Martin L. - Official Prusa CS -

Challenge accepted. Where are the design files for the buffer plates? I could only find the printable pieces that go on the ends when I looked here: https://www.prusa3d.com/downloads/others...

Jeff Gros -

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