BUFFER UNIT - Made for Prusa MMU3

ⓘ If you don't have screws with the right length, slightly longer screws work as well!

See extra parts for your specific printer setup:

• Buffer Unit for MK4/MK3
• Buffer Unit for Original Prusa Enclosure
• Buffer Unit for COREBOXX
• Buffer unit for CORE One (coming soon)

Seams: “Scarf joint placement” to: “Everywhere” in PrusaSlicer.

⚠ IMPORTANT! Spools may get stuck on the seams if you don't use this setting. 

The manual is split into two parts:

1. Assembly of the BUFFER UNIT
2. Mounting the BUFFER UNIT to your specific printer

The second part can be found for free on my Printables Page:

• BUFFER UNIT for MK4/MK3
• BUFFER UNIT for Original Prusa Enclosure
• BUFFER UNIT for COREBOXX
• BUFFER UNIT for CORE One (coming soon)

Prepare the following tools:

2.5mm Allen key (for M3 screws)

PTFE-cutter/Cutting pliers

Measuring tape (for measuring PTFE-tubes)

Please prepare the following items:

R-Shell (1x)

Bearing (3x)

M3 hex nut (5x)

M3x18 screw (2x)

M3x12 screw (1x)

🟠Insert 3 hex nuts through the slots on the R-Shell. Press the nuts with a hex key to ensure proper insertion. 

🟡Insert the remaining 2 M3 hex nuts according to the picture.

🟠Snap 3 bearings into place on top of the R-Shell's pins.

🟡Secure two of the bearings with two M3x18 screws according to the picture.

🟢 Secure the last bearing with a M3x12 screw.

Prepare the following items: 

R-Front-roller (1x)

L-Front-roller (1x)

Front-roller-
sleeve (2x)

M3 hex nut (1x)

M3x40 screw (1x)

⚠ If you have rollers without TPU-sleeves, skip the parts attaching these. 

🟠Insert the M3 hex nut through the hole of the R-Front-roller.

ⓘ To make insertion easier, take a long screw (e.g. M3x40) and thread the nut slightly. Then use the screw to insert the nut.

🟠Connect the R-Front-roller to the L-Front-roller.

🟡Insert the M3x40 screw through the R-Front-roller. Tighten it. 

Please prepare the following items:

Spur-gear (1x)

Bearing (1x)

M3x18 screw (1x)

🟠Attach the bearing on top of the Spur-gear. 

🟡Secure it with a M3x18 screw from the other side. 

Prepare the following items:

Back-roller (1x)

Back-roller-sleeve (1x)

Arm-R (1x)

Arm-L (1x)

Ring-gear (1x)

Bearing (2x)

M3 hex nut (2x)

M3x18 screw (2x)

M3x12 screw (2x)

🟠Take the R-Arm and L-Arm and snap one bearing onto each one. 

🟡Insert and tighten M3x12 screws from the back, securing the bearings into place.

🟠Slide two M3 hex nuts into each slot on the R-Arm. 

Press the nuts with a hex key to ensure proper insertion. 

🟠Push the Back-roller into place on top of the L-Arm's bearing.  

ⓘ The Front-roller is unidirectional 

Let's attach the Arm-assembly to the R-Shell!

🟠Align the Arm's right hole with the bearing seated on the R-shell. 

🟡While doing this, rotate the arm so that the Ring-gear can freely pass the Front-roller and mesh with the Spur-gear.

🟠+🟡Press the Arm-assembly into place. 

Please prepare the following items:

L-Shell (1x)

Bearing (2x)

M3x18 screw (1x)

M3x12 screw (1x)

M3x10 screw (3x)

🟠Snap 2 bearings into place on top of the L-Shell's pins. 

🟡Secure one of the bearings in place using a M3x18 screw.

🟢Secure the other bearing with a M3x12 screw. 

Press the L-Shell on top of the Module-assembly. 

🟠Secure it with 3 M3x10 screws according to the picture.

Let's test the buffer before further assembly. 

🟠 Release the arm-assembly in the uppermost position. It should slowly fall down, turning the front-roller by its own weight. 

🟡Place a 1 kg spool of filament on the rollers. Roll it manually and watch as it lifts up.

🟢Release the spool very gently. It should smoothly roll back

ⓘ The Buffer-module is now done.

You've assembled 1 out of 5 modules. 

🟠Follow the previous steps to assemble 4 more Buffer-modules, for a total of 5 modules. 

Please prepare the following items:

M3x10 screw (8x)

🟠Align two Buffer-modules with each other. 

🟡Attach them with two M3x10 screws. 

🟠Repeat the previous step with the other modules, connecting them all together. 

You're now done with with part 1 of the assembly! 

Continue assembly for your specific setup:

MK4/MK3

Original Prusa Enclosure

ⓘ The CORE One specific setup is coming in the future. The buffer can still be used for the printer, but not with specific mounting options.

Update 7 April - Version A4

I've gathered feedback the last couple weeks and concluded that the bearing pins needed an overhaul. Some users experienced extra friction in the mechanism, only to find out that the these pins were damaged. So here it is! Version A4 now has new strong cylindrical pins with slightly bendable parts to hold the bearings in place. I also took the opportunity and updated the Side-panel pins to also be stronger, incorporating the same kind of design. Furthermore, this version includes much higher STL-quality, allowing smoother surfaces for the Rollers. Here's a summary:

• New, stronger bearing pins that won't break
• Stronger Side-panel pins
• Higher quality STL-files ✨ →  smoother Roller-surface

If you have any thoughts on the design or encounter any problems, please reach out to me and I will try to fix it in the next update! 

Update 30 March - Small improvements

I have implemented some things to improve printability. The “bearing-pins” are less likely to break now with stronger connections and bigger hole for the screws. R-Front-roller is also easier to print with adjusted overhangs. 

Update 27 + 28 March - Custom setups and support for COREBOXX

Now you can officially install the BUFFER UNIT inside the COREBOXX. You can find the setup by clicking here!

Many people have also asked if the buffer unit can be used with other printers, enclosures and MMU:s. The answer is yes, and now you can find basic STEP-files for free here to create custom brackets/mounts! They also include PTFE-guides numbered 6-12 for MMU:s with higher filament counts (like the ERCF for example).

Update 23 March - Version A3 

I've been working non stop since the release last week, gathering user input from many of you. Again, thanks so much for the support! This update includes lots of improvements, the main one being the addition of TPU-sleeves for the rollers. This improves friction and makes the rewinding more reliable (special thanks to @BrianAmato_717081 and especially @LucianFlorin_1026103 for suggesting it!). Here’s a rundown of some of the improvement:

• TPU sleeves for all rollers - improves friction with spools, more reliable rewinding.
• New complaint M3 hex nut slots that make inserting nuts way easier. 
• Less pressure on the PTFE-tube from the PTFE-Guide’s locking lever, reducing friction on filament. 
• Added 3MF files for multi-material-parts. 
• Now supports 686 ZZ bearings in addition to the 685 ZZ
• + more small changes

I’m now starting my work on an official Buffer Unit video. I believe I have ironed out most of the common problems some have experienced, but if you have more input please contact me and I’ll make sure to address these in the next update. In addition to the video, I’m now turning my attention to the publishing of the setups for CORE One and COREBOXX.

ⓘ See part compatibility for the new version down below under “printed-parts”.

Update 20 March - Version A2

Thanks to everyone who have purchased the Buffer Unit! I'm working hard to make the Buffer Unit the best it can be. Here are some improvements:

• Small changes for improved printability and assembly.
• Added slot to R- & L-Shell for attaching buffer unit to future CORE One and COREBOXX brackets.
• Improved PTFE-clips and routing.
• Stronger connection between Ring-gear and Arm-assembly. 
• I'm currently working on TPU-sleeves to improve roller friction with spools.

ⓘ Old files are still available. Old Ring-gear, R- & L-Shell, R- & L-Arm and Side-panels are not compatible with the new A2 Version. 

Update 12 March - Version A1

• First release!