Multi color printing with Prusa's MMU V2 & Duet?



  • Prusa is releasing the MMU V2. The MMU comes with it's own electronics, but I guess it won't be compatible with the Duet. If the MMU v2 can be adapted to the Duet boards, it looks like it could be an affordable multi color printing option. What I like is that it doesn't add any mass to moving parts.

    I'd like to know what would be needed to make it work with a DUET board.

    • expansion board
    • ?

    edit: Found this pic on the net:

    0_1532350433658_eSn91ju.jpg


  • administrators

    It looks to me that it uses one additional stepper motor to select which pinch roller to engage the the filament, and one more to select the correct filament output. Assuming that there are homing switches for each of those stepper motors, I don't see why any firmware changes or additional electronics would be needed. You could define those two stepper motors as additional axes, home them along with the other ones (with the filament retracted from the outlet), and configure the tool change files to set the correct positions of each of those axes. The description mentions a cutter too.

    Have they open-sourced the electronics that it uses yet?



  • @dc42 said in Multi color printing with Prusa's MMU V2 & Duet?:

    It looks to me that it uses one additional stepper motor to select which pinch roller to engage the the filament, and one more to select the correct filament output. Assuming that there are homing switches for each of those stepper motors, I don't see why any firmware changes or additional electronics would be needed. You could define those two stepper motors as additional axes, home them along with the other ones (with the filament retracted from the outlet), and configure the tool change files to set the correct positions of each of those axes. The description mentions a cutter too.

    Have they open-sourced the electronics that it uses yet?

    I had a quick look at github, but didn't find anything. Maybe its there somewhere.
    I think it uses 3 additional steppers, so at least you'd need a Duex with 2 extra ports if you can use the second extruder port on the Duet?

    • 3 steppers on the MMU v2
    • 1 stepper for the extruder


  • Gathering a bit of information from Youtube and blog posts, I think the MMU2 has its own electronics, with some selection buttons on top of the unit.

    Since it is supposed to be an upgrade for the MK3, which uses the Einsy board, I would expect the MMU2 to be fully self-contained, and probably uses a simple interface to communicate with the main controller (SPI/Serial or similar). Maybe it requires a small adapter board to connect to Ext P1-P3.

    Shipment of these units was delayed multiple times already and is currently planned for September 2018.

    No open-source documents have been published so far.

    Once Prusa actually ships the thing, and publishes more documents, we can think about if and how this would work with a Duet controller.
    Until then - we can only guess.



  • Small reference on github: https://github.com/prusa3d/Arduino_Boards/blob/master/IDE_Board_Manager/package_prusa3d_index.json

    But, maybe possible to use without prusa's board? Just directly connect to Duet and just use the mechanics?



  • Any here buy the mmu2 and plans to use without the original prusa?



  • Looks like prusa released a promotion video
    https://youtu.be/E1ZxTCApLrs



  • Also interested in (eventually) trying to get this to work with my cartesian printer for use with dissolvible support material, anyone find out any more info on how it would be possible to get it working with the Duet?



  • Look at the main board sources:

    https://github.com/prusa3d/Prusa-Firmware/releases/tag/v3.4.0-RC2

    there are 2 files, mmu.h and mmu.cpp which handle the com with the MMU board. Looks like they use a serial port.

    I guess it is possible to include support in the Duet? It would require to use the PanelDue connector...



  • Wouldn't it be easier to just plug the steppers into a duex expansion board and write some custom macro's? That way you don't need prusa's electronics.



  • Yes. As David said, this solution can be implemented without any modifications. But you will loose some features, like checking if the filament is correctly engaged (with the switch made from a metal ball and inductive sensor) or so. And no feedback at all: if it jams, the Duet won't be noticed, and will continue to print...



  • @fma couldn't you plug that sensor in the duet?



  • Yes, but how to manage it? There is not condition testing in G-Codes...



  • A good point in this MMU v2 is the non Bowden configuration: the multiplexer is only used to load/unload filaments to the extruder.

    I'm wondering if we could use it without the carriage selector, and use the passive splitter of the v1? This would need more tubes between the unit and the extruder, but it would be much faster to switch from one filament to another, and reduce the chance of jamming (at the input of the carriage)?

    And the Duet integration would be much easier.

    What do you think?



  • @fma I think part of the multi color precision of the v2 comes from being direct drive versus bowden. So there's that.

    I'm not sure you need conditional gcode and variables to make it work... couldn't it be scripted with macros as they are?

    Even so, conditional gcode is being hinted at for the near future, so maybe it won't be long to wait.



  • @phaedrux said in Multi color printing with Prusa's MMU V2 & Duet?:

    @fma I think part of the multi color precision of the v2 comes from being direct drive versus bowden. So there's that.

    My suggestion does not change that point: the MMU is still used to load/unload filament, extruder remaining on the printer carriage. But instead of having the moving selector, and only 1 PTFE tube, there is n PTFE tubes, and a splitter n-to-1 above the extruder.

    Even so, conditional gcode is being hinted at for the near future, so maybe it won't be long to wait.

    That's good news!



  • Firmware for the MMU board has been published, as also the schematics of the board.

    Looking at the slic3r profiles, there is a 'ramming' function. Apparantly this is to retract filament with a clean cone and no strings to avoid jamming.



  • Great!

    Does anyone understand how 'ramming' params work?





  • Yes, but what if the input is never triggered?


 

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