MMU3 printable parts R4 (F1)

Jakub Dolezal

(@jakub-dolezal)

Member Admin

MMU3 printable parts R4 (F1)

Hi,

Together with the release of the MMU3 upgrade for MK4 & MK3.9, we are also releasing updated printable parts. Please read the following text carefully, it explains all possible MMU3 combinations and describes changes in the printable parts. If you are already running your MMU3 setup, reprinting parts won't bring any significant difference.

MMU3 combinations

MMU3 is currently compatible with the following printers:
- Original Prusa MK3S+
- Original Prusa MK3.5
- Original Prusa MK3.9
- Original Prusa MK4

The MMU3 consists of 4 major parts:
1. Spoolholders
2. Buffer
3. MMU unit (incl. power/data cable)
4. MMU parts for the (N)extruder

The MMU3 was designed to be compatible with all the printers listed above, however, there are some parts, which are unique to each printer model. For example, if you want to move your MMU3 from MK3S+ to MK4, you have to change the power/data cable, upgrade some printable parts and get parts for the Nextruder.

To make your transition easier, we have prepared these upgrade sets:

MK3S+ MMU3 to MK3.5 MMU3 => e-shop link
MK3S+ MMU3 to MK4/MK3.9 MMU3 => e-shop link coming soon

Printable parts F1/R4

Printable parts from this “MK4 release” iteration are marked either F1 (printed on Prusa farm) or R4 (available on Printables). It's important to note that there is no functional difference between F1 and R4 parts. The different markings are solely intended to help our colleagues from support with eventual troubleshooting.

Now, let's go through the four major MMU parts and explain the differences:

1. Spoolholders

The MMU3 was originally shipped with vacuum-formed spool holders, consisting of steel bearings and aluminum rods. These spool holders are compatible with all supported MMU3 and printer combinations. You can continue using them, even if you move your MMU3 to a different printer.

MMU spoolholders: Vacuum-formed (on the left, yellow arrow) and Injection-molded (on the right, blue arrow)

At the beginning of 2024, we introduced an updated injection-molded variant of the spool holders, offering improved spool arrangement and the ability to connect the holders together. These new holders are compatible with all supported MMU3 and printer combinations, with a small exception. After months of extensive testing, we found that worn wheels could potentially lead to loading issues specifically on MK4 and MK3.9 setups. As a preventive measure, we've upgraded the material of the wheels, and MK4/MK3.9 MMU3 packages will now include these updated wheels. If you're using MK3S+ and MK3.5 setups, there shouldn't be any issues. However, if you're upgrading your existing MK3S+ MMU3 setup to MK4/MK3.9, we recommend changing the wheels (wheels are part of the upgrade package).

Conclusion: There are no changes in the MK3S+ and MK3.5 setups. However, for MK4 and MK3.9 setups, it's recommended to change the new spool holder wheel for the injection molded variant (part of the upgrade package).

2. Buffer

The buffer consists of plastic plates and printable parts. During the testing of the MK4/MK3.9, we discovered that the space inside the buffer is slightly smaller than needed. To keep the compatibility across all printers, the plates will remain unchanged, but we have updated the printable parts. Specifically, the cassettes were slightly repositioned outward from the buffer, resulting in increased internal capacity.

Leg (R4)

There is no change to this part, no need to reprint existing setup.

Plate-holder (R4)

There is no change to this part, no need to reprint existing setup.

Printer-holder (R4)

There is no change to this part, no need to reprint existing setup.

Segment (R4)

If you are upgrading your current MMU3 setup to MK4/MK3.9 you have to reprint this part. Additionally, you'll need to print the Segmenter (R4).

Segmenter (R4)

If you are upgrading your current MMU3 setup to MK4/MK3.9 you have to reprint this part. Additionally, you'll need to print the Segment (R4).

Wheel (R4)

There is no change to this part, no need to reprint existing setup.

Conclusion for Buffer : There are no changes in the MK3S+ and MK3.5 setups. However, for MK4 and MK3.9 setups, it is recommended to use the new cassette design. Cassettes with their updated dock, called segmenter, can be reprinted from PETG.

3. MMU unit

The MMU unit consists of multiple printable and mechanical parts. While there are no changes to the mechanical components (such as motors, pulleys, main MMU board, etc.), nearly every printable part of the MMU unit has been updated. This doesn't mean that you have to reprint your existing MMU unit. These changes primarily focus on improving printability and refining the dimensions of openings, thus allowing for even better assembly. For the MK4/MK3.9 we are introducing a new part, which can be applied to the older setups improving the ESD protection. You can find more information below.

Blade-holder (R4)

This part has been updated, and the new version offers slight improvements in two areas. First, the blades are now slightly tilted to reduce the resistance and the screw is brought closer to the blades to provide more grip. However, if your current blade holder is working fine, there is no need to reprint it. Please note, that this part must be paired with Selector and Pulley-body (both R4).

Collet-holder (R4)

There is no functional improvement in this update. The developers have changed only the position of the arrow. If your collet holder is working properly, there is no need to reprint it.

Ele-cover (R4)

This part is responsible for securing the MMU control board. The new iteration is improving protection against electrostatic discharge (ESD) together with a new printed part PD-board-cover (described below). During the laboratory tests, we discovered that the MK4/MK3.9 electronics are more sensitive to the ESD. To ensure sufficient protection in all possible conditions, we have updated this part. If your working environment charges you up with “energy”, we recommend updating these two parts on your existing setup. They are compatible with surrounding R3 parts.

PD-board-cover (R5)

As described in the previous section, this new cover improves protection against ESD and must be paired (printed together) with Ele-cover (R4).

Frame-holder (R4)

There is no functional improvement, there is no need to reprint this part.

Front-PTFE-holder (R4)

Based on the feedback from the community, the design of the openings for PTFE tubes was improved. The seams were moved further away from the opening, ensuring easier assembly regardless of whether the part was printed on Prusa farm or at home. Reprinting this part for existing setups is not needed.

Idler (R4)

While updating the parts, we have also refreshed the idler. Some users reported that the pin closest to the outside bearing seemed to be too loose. The design was updated and the hole for the pin is now tighter. Updating existing setups is not required unless your pin is loose.

Idler-body (R4)

There is no functional improvement, there is no need to reprint this part.

Label-plate (R4)

There is no functional improvement in this update, so there is no need to reprint this part. Additionally, the Label-plate is included in all packages because post-processing (labeling) is done at our factory and cannot be easily replicated at home.

PTFE-clip (R4)

There is no functional improvement, there is no need to reprint this part.

Pulley-body (R4)

Similarly to the Front-PTFE-holder the design of the openings was improved. In this case to enable easier assembly of the smooth rods. Ensuring that the selector will move without any resistance. If your MMU3 unit is working as expected, there is no need to reprint this part.

Selector (R4)

The design of the selector is bound to the Blade-holder mentioned earlier. Another change was made to the openings for smooth rods, where the tolerance was tightened to improve the grip of the "golden" bushing tubes.

Selector-front-plate (R4)

There is no functional improvement, there is no need to reprint this part.

Conclusion for MMU unit: For the existing MK3S+ and MK3.5 setups there is no need to update the parts. The only thing to consider is printing the updated Ele-cover with PD-board-cover. Owners of the MK4/MK3.9 should print the R4 revisions. However, if you have pre-printed the R3 parts, print the R4 versions of the Ele-cover and PD-board-cover.

4. MMU parts for the Nextruder

All the parts below are included in the MK4/MK3.9 MMU3 packages, regardless if you have selected MMU3 with or without printed parts. There is no need to print them.

Idler-lever-A (R2)

This is a brand new part for the MMU MK4/MK3.9 Nextruder designed to replace the existing lever. Long-term testing has shown that this part performs best when printed from PCCF or similar material, therefore it is printed on Prusa farm and included in all packages. However, an STL file will be available to download on the Printables.