The main difference between this and other mods is that it uses the stock buffer unit and encloses it within the enclosure itself, making the entire setup self-contained. I originally built the enclosure for the MK3S+/MMU2S in late 2023/early 2024. I've since upgraded the printer and MMU to MK3.5/MMU3, and it fits just as well. The mod should equally work for MK4/MK4S with the MMU3.
This guide may be incomplete because I don't have all the information to hand at the moment. This build was done over several months, on and off. I went over many iterations of trials and errors during that time. I didn't keep a good record of that build process, so don't necessarily remember which models I ended up using and which ones I ended up discarding. I will go back to determine the sources for the final build and update this guide accordingly.
This guide is brief because I don't have time to write a comprehensive guide for now. I'll come back and add details later when I have time.
Assuming you already have the MMU3 including the buffer unit, print:
You'll also need the following (*I got these from RS Components):
Insert festo fittings into the quad filament connector and dual filament connectors. Install the quad filament connector on the top right, close to the front, with an M3 x 18 screw and M3n nut. Install the dual filament connectors on the top left and top right, close to the rear.
The PTFE tubes connect the front filament guides at the front to the festo fittings in the quad filament connector on the top right of the enclosure. Insert the PTFE tubing into the front filament guides and route them behind the top front and top right of the enclosure for spools 1-4, and insert the other end into the quad filament connector, like this: https://i.imgur.com/E0LoIh8.jpeg. Feed the filaments through the filament guides at the front, through the PTFE tubing and quad connector, into the buffer unit.
For spool 5 (rear top left), connect the PTFE tubing between the two dual filament connectors via the festo fittings. Route this around the top rear of the enclosure. Insert a 15-25cm PTFE tube on the other side of the dual filament connector and leave it dangling. Load the filament clockwise, and feed the filament front to rear by inserting it into the dangling end of the PTFE tubing, like this: https://i.imgur.com/KaXcjX5.jpeg.
For the buffer, no need to attach the leg. Place the buffer where the printer PSU used to be, with the segments/cassettes facing up: https://i.imgur.com/nvIaeBk.jpeg. Connect the segments/cassettes with the PTFE tubing to the quad/dual filament connectors on one end, and to the MMU on the other. Avoid abrupt bends in the PTFE tubing - a larger radius is better for lower friction. I'll update the guide with PTFE tube length later.
For single-filament non-MMU mode (for using the printer with the MMU disabled), use the remaining slot in the dual filament connector closest to spool 5 (top rear left). Attach a PTFE tube from the front-facing festo fitting in the dual filament connector to the extruder. Insert a segment of 10-15cm PTFE tube into the rear-facing festo fitting and leave that end dangling. Load the filament anticlockwise, and feed the filament into the dangling PTFE tube, from the rear to the front of the enclosure. When printing with the MMU disabled, use spool 5.
More details later. See photos for now (photos with captions here). Some photos are of the older MK3S+/MMU2S setup, but it's pretty much the same for compatible MK3/4 series + MMU3 setups.
To move the LED strip to the top, I had to extend the cable. The longest cable I could find was 600mm, but even that was still a few cm too short. I ended up buying two of that, cutting them and soldering them together. I then replaced the short stock cable with the longer cable.
This mod was originally shared on Reddit. It uses various models from other authors, in combination with some models that I've created myself. The models uploaded here are my own. Links are provided to models sourced from other authors.
STL and FCStd files are provided. The FCStd files are editable in FreeCAD.
These are used as-is:
The following parts are optional. If you have the original MMU3 parts, you don't need these. I used them initially when I first adopted the MMU3 buffer unit to use with my MMU2S. I had printed all plastic parts to assemble the buffer but I still needed the metal pins and the metal collettes. I didn't have the MMU3 upgrade kit at the time so I looked for printed alternatives and found these, which worked great:
I printed these parts in generic PETG, typically at 0.20mm layer height, 15-20% gyroid infill, without supports. The spool holder arm was printed at 100% infill.
The author marked this model as their own original creation.