Multi color printing with Prusa's MMU V2 & Duet?
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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...
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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.
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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...
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@fma couldn't you plug that sensor in the duet?
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Yes, but how to manage it? There is not condition testing in G-Codes...
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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?
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@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.
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@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!
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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.
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Great!
Does anyone understand how 'ramming' params work?
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Regarding conditionals, couldn't something like this be used with the filament sensor of the MMU: https://reprap.org/wiki/G-code#M226:_Wait_for_pin_state
or: https://reprap.org/wiki/G-code#M577:_Wait_until_endstop_is_triggered
or: https://reprap.org/wiki/G-code#M583:_Wait_for_pin -
Yes, but what if the input is never triggered?
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@fma why would the sensor not be triggered?
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If case the filament does not engage correctly in the carriage, because of melted end (blob).
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I guess that's why 'ramming' needs to be tuned properly.
Anyway, with those available gcodes should it not be possible to write some custom macro's?
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Yes, sure! This is simple motors, so a couple of G1 commands should do the job. And the carriage needs to be homed.
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I don't see any homing switches so I guess it relies on sensorless homing
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Right. It uses TMC drivers...
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If it uses sensorless homing normally, wouldn't installing a normal endstop switch correct for that issue?
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Yes, sure. And it should be easy to do.
