MMU3 mounting kit for Original Prusa Enclosure

I wanted my MMU3 buffer and spools to be entirely contained within the Prusa Original Enclosure.  So I made a few parts to help:

• Buffer plate holders to use as mounting brackets (above or below the hinged lid)
• Filament guides for both corners, with multiple entry points
• Thermometer bracket
• Mountable, grippier PTFE clips
• Top plug with 10 PTFE pass through holes

In detail:

1. Modified MMU3 Buffer Holders that double as brackets to hang the buffer from the underside of the enclosure lid (or to mount it on top of the lid - see 23 April 2024 update below) using existing holes in the lid. Two sets of four brackets are included as STLs: one set places the buffer in the centre of the lid, while the other set moves it 30mm further towards the back of the enclosure to create a little more space for filament spools at the front of the enclosure. This is the version that I have used, and that is shown in the photos.  The OpenSCAD script is included in case you want to adjust the position of the buffer to your own requirements.
   
   The STLs are provided in the correct orientation for printing (not as shown in the two images below), and the first set (which centres the buffer) can be printed without supports.  In the second set, which moves the buffer further back, the angle of the front two brackets is a lot more shallow, so build plate supports are needed for those two brackets.
   
   Update 29JUN24: I've now included versions of the centred and shifted brackets that are based on Saphir's modified buffer plate holders that allow them to be screwed onto the buffer plates in a similar manner to the segmenter plate.
   
   
   
   
    
2. Two modified filament guides to take more than one PTFE tube, and to angle the tubes towards the outer edges of the enclosure for a smooth filament path. STLs are provided with three tube positions in the top right corner and two in the top left corner. Use the corresponding ‘numbers’ STL to print the numbers in a different colour if you wish.  The OpenSCAD script will be uploaded soon in case you wish to change the number of tube positions in each corner, or in case you wish to change the number markings.  
   
   
   
   
   
   
    
3. Since the guide in the top left corner takes the place of the original thermometer bracket, I have also included a modified thermometer bracket to allow it to be mounted next to the filament guide, using the next (slightly wider) pair of screw holes.  The bracket uses the same frame as Prusa's Adjustable Thermometer Bracket, so you'll need Thermometer-B.stl from that model.
   
   
    
4. Some modified PTFE clips with a variable number of tube slots, and with the option to slightly reduce the slot diameters to improve the grip on the tubes.  Two STLs are provided: one with two slots and one with three (to suit the proposed arrangement of two feed points on the left and three on the right).  I have also provided a 5-slot version in case you just want a tighter grip for the clips between the MMU3 and the buffer.  I have also provided 2-slot and 3-slot versions with added fixing points that allow the clips to be screwed to the outer edges of the enclosure, to help with routing the PTFE tubes.  All the provided STLs have a slot diameter reduced by 0.2mm, which seems to improve the grip on the tubes just enough.  I have included the OpenSCAD script in case you want modified clips with different numbers of slots, or you want to adjust the grip.
   
   
   
   
    
5. A modified top plug to allow 10 PTFE tubes to pass through (in and out, x5 buffer segments) in case the buffer is mounted on top of the enclosure lid.
   
   

I use these parts in combination with my spool holder, which allows me to mount spools in any corner of the enclosure.  I have two spools in the top right corner, and one in each of the other three front corners.

Update 23 April 2024:

I have now moved my buffer to the top side of the hinged lid, using the same brackets.  I realised that the lid could no longer be used as a shelf, due to the need to open it occasionally to load filament or access the MMU3 unit, so I felt there was no particular benefit in having the buffer inside the enclosure.  Mounting the buffer on top of the lid, using the same brackets, allows filaments to be loaded without having to open the lid, and it means that the tube between the MMU unit and the Nextruder no longer comes into contact with the buffer at high Z positions.

I have added a top rear plug that allows the 10 PTFE tubes to pass through the hole in the rear centre of the lid.

I found that the bracket set that best suits a top-mounted buffer is actually the set that centres the buffer on the lid, since this gives a gentler bend radius for the tubes to go from the segments to the inside of the enclosure.

The 95cm PTFE tubes (see Mounting Tips below) from the spool feed points to the buffer will still work, as will the 45cm tubes from the buffer to the MMU, but both could do with being a few cm longer with this top-mounted buffer, so I'd suggest using a full metre and 0.5m respectively.
 

Mounting Tips

You'll need to convert the lid of your enclosure to the hinged lid version, but that's necessary when using the MMU3 anyway.

The 650mm PTFE tubes supplied with the MMU3 aren't well suited to mounting the buffer and spools as pictured.  The tubes from the spools to the buffer segments need to be longer to achieve a smooth path around the inside edge of the enclosure, as pictured.  The tubes in my photos are 950mm long (although when mounting the buffer on top of the enclosure lid, these tubes would benefit from being a few cm longer, so I suggest using 1m tubes).  Conversely, the tubes from the segments to the MMU3 unit are longer than they need to be for this setup.  I have used 450mm tubes (and when top-mounting the buffer, these could also benefit from being 5cm longer).  The total path length in this setup is therefore 950+450 = 1400mm (or 1500mm).  This is 100mm (or 200mm) longer than the path with the supplied tubes, which should not cause a significant increase in friction.  To mitigate this further, all the tubes I have used are 3mm ID x 4mm OD, whereas the supplied tubes have an internal diameter of 2.5mm. When routing the PTFE tubes it is important to maintain as smooth a path as possible, with the maximum bend radius that you can achieve.  Take care in the corners immediately after the filament guides - push the tubes up into the corners to ensure that the exit from the filament guides is smooth.  Use plenty of the mountable, tighter PTFE clips to ensure that the tubes don't move.

With the buffer mounted this way, accessing the buffer segments requires the hinged lid to be opened fully vertical (or it needs good access to the top rear of the enclosure if the buffer is top-mounted), and it can be fiddly accessing the separate segments to feed the filament. The solution to this is to use Saphir's brilliant loading fork.  With this tool, the lid needs only to be cracked open sufficiently (or not at all if it is top-mounted) to insert the tool, and then filament can be fed directly from the feed point to the MMU3 unit without removing the segments. Saphir now has a version of the loading fork that works with the R4 segments suitable for the MK4, and it works very nicely.

Caution

There are a couple of things to be aware of with this setup.

Firstly, 3mm ID x 4mm OD PTFE tubes are not as robust as the 2.5mm ID tubes. They kink more easily, so they need a certain amount of care when routing them to the buffer, particularly if routing them to a top-mounted buffer - take care with the bend radius between the segments and the pass-through top plug.

Secondly, if the buffer is mounted on the underside of the lid, the PTFE tube between the MMU and the Nextruder will come into contact with the buffer when the Z-axis is above about 75mm.  At maximum Z, the tube will be deflected over quite a lot.  I found that the Nextruder would still move along the full range of the X-axis at this height, so I don't think it would cause a long term problem, but it's something to be aware of.  Of course, this issue goes away if you mount the buffer on top of the lid.

1. Modified the MMU3 Buffer Holders to become mounting feet.
2. Modified the filament guide to take more than one PTFE tube, and to angle the tubes towards the outer edges of the enclosure. Also mirrored it to provide additional filament guides in the top left corner.
3. Modified the thermometer bracket to make room for the top-left filament guides.
4. Modified the PTFE clip to have a variable number of tube slots, with reduced slot diameters to improve the grip on the tubes. Also added fixing points to allow the clips to be screwed to the outer edges of the enclosure.
5. Modified the top plug to pass through 10 PTFE tubes, for when the buffer is mounted on the top of the enclosure lid.

N.B. This kit includes remixes of Prusa's enclosure parts and Prusa's MMU3 parts.  However, those two models have different licences (GPLv2 and GPLv3), and no single licence is compatible with both according to Printables.  I've therefore had to remove one of them from the list in order to be able to publish my model.  I removed the MMU3 because the enclosure uses GPLv3, which seems to cover the intent of GPLv2 (as used by the MMU3).