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

bartolomeus

@dc42 for me the benefit of the mmu2 is that it remains direct drive, and doesn't add mass to the X carriage.

deckingman

Just to add something to the mix, there is a company called RD4 which makes a multi filament feeder. It's called the RDB. They did approach me and asked if I would be willing to test one of their units, which I agreed to do. I signed a Non-Disclosure Agreement with them but alas they never did send me a unit or provide me with any information (if they had, I could not of course divulge anything). I note however that they have a stand at the TCT show so I'll stop by and see what's what.

Yet another alternative is the Pallete2 system by Mosaic.

Finally, the cheapest option is to pause the print, retract the filament, load new filament, purge and resume. Essentially, that is all that any of these systems do albeit in a semi automatic way. Unlike the Diamond and the Quad (and to some extent the pallette2) which have all the filaments loaded so switching between them is simple a matter of changing tools (which can be done "on the fly" without pausing the print).

martinj

I've made an MMU2 unit from some scrap parts I had laying around just as a Proof of Concept to see how if i could get it to work with Duet.

I haven't implemented any tramming which i do believe is important to avoid jams especially stringing is a problem.
I also think for it to be sort of reliable it needs to use some sort of filament sensor to check if the switch is successful or not so the print may be saved through manual intervention, though I haven't really found a way to solve this with Duet. I really would like to have some sort of conditional checking.

brunofporto

If the objective is just add collors one can create a multi pen filament colorizer (like this https://www.thingiverse.com/thing:11742 but with all colors you want)

Also I discussed with a friend to have a special tool that holds a pen (grabbed from a 100 color carousel) and just draw each layer perimeter with the color you want

JLink33

Hi, I built my own MMU2 and configured the Selector and bearing rotation mechanism with endstopless homing, but I cannot figure out how to configure the extruder drive motor with the five drive gears. How do I do that on the duet. What commands do I have to add to my config.g. Thanks

dc42

I am not familiar with the MMU2. Can you explain in more detail what the requirement is?

martinj

@dc42 the most critical actions for mmu is during unload/load of a filament where it could slip or jam. The way MMU2 handles it is to use a filament sensor to detect potential problems during load/unload.

Example when loading, move filament forward and check status of filament sensor. If doing this for X step and the filament sensor doesn't detect the filament you would do a retry phase, e.g back filament some and retry and if still doesn't succeed pause print for manual intervention.
Same principal would be used for unloading to verify it succeeds.

Unfortunately I don't see a way to solve this with Duet with its current functionality, and I don't have any suggestion on how it could be solved using GCode. Wish there were some sort of advanced scripting support.

fma

What about moving the intelligent script out of the Duet?

connect all motors to the Duet/Duex;
connect an arduino to the Due connector and to the I²C bus; also connect the filament contact on the MMU carriage to that arduino;
write a Duet macro to send a specific code over I²C when filament change is needed, and pause the print;
send required G-Code to the Duet to move the motors, check the sensor, do the retries if needed...
send a resume command to the Duet.

Note 1: you may use an esp8266 and control the Duet over wifi instead of serial;

Note 2: this arduino/esp could also communicate with the original MMU electronic, over SPI, so you don't need a Duex. As Prusa board firmware is open, you could re-use most of its code to handle the MMU electronic communication. The only thing to do is to sync Duet and MMU.

martinj

@fma It was actually my initial thought when i was thinking of making a MMU2. Connect and run everything externally. However it does increase the complexity, was hoping to be able accomplish it only using the duet.

fma

Well, most of the code is already written in Prusa main board firmware, so there is not that much work... More adding some glue ;o)

Bester42

@fma I think its even more simple, if you use an arduino.
Simply connect the arduino to DIR and STEP of the extruder driver. Let the Arduino count steps every time DIR is in backwards direction (reset counter if a step is done forward). If the number of steps exeed a certain number, obviously its not retraction but filament unload.
So the command to change filament is unload filament.
The arduino than sends the command to retract the filament into the MMU to the controller of the MMU.

To select the new filament, let the extruder step into forward direction for 1-5 mm. This does effectly nothing, as the extruder is empty. But the arduino can interpret this as "I want filament 1-5", so command in gcode would be extract 1mm filament to select filament one. The Arduino than sends the code for Filament selection to the MMU.

Than let wait for Filament change completed by the MMU. Than the arduino triggers a gpio on the duet; in gcode its an m226 to wait for this pin. Than start loading (if your printer has autoload, this is notneeded, simply use m600 insted).

This technique may work not only with a Duet, but with nearly any 3d fdm-printer, even the cheapest ones - if you dont have access to dir/step signals, use an optical encoder on the extruder-motor, if you do not have a free gpio or autoload-function, set a relais in parallel to the O.K.-Button and use m600.

Only think is calibration. You may do that by terminal via Arduino to the mmu.

fma

I agree, this is a good solution...

In fact, there is already an Arduino in the MMU2! Don't know if there are enough inputs, but it could be interesting to just have to modify MMU2 firmware to implement your proposition...

Bester42

You are perfectly right.

The reason to use an extra Arduino (clone) is Prusa Research contantly improving and updating not only the printers firmware, but also firmware of mmu.
So by adding an extra Arduino (Clone) you add only a cost of 3-4€, but making maintence much more easy.

Also an Arduino is not an multitasking system. So checking gpio's, constantly control extruder movement, you have to make shure not to interfeare with the mmu's functions. So it would require much more programming skills.
Using an extra Arduino the code would be much more easy. It's strictly single task.

Watch rotation of extruder
If unload detected, send comand to mmu
Watch rotation of extruder
If movement (1-5mm) detected, send comand to load and Insert filament 1...5
If a filament sensor detects Filament Inserates (or mmu tells thad loading ist completed) give signal to the printer.
Goto 1.

I do not think Prusa will change comands a lot in future (maybe add "success" comand from printer if the printhead filament sensor detects loaded filament - but due to bad relability of prusas sensor I do not think this coming soon). So an "Interface-Arduino" is much simplier than modding mmu-firmware, much more easy to modify.

gavatron3000

Might be another idea to use this fellas version of the firmware for Arduino but modify it to change via multiplexer or a digital IO somehow. That way the duet initiates the changes but it fully controlled by the Arduino. He's also added another sensor to the system
https://github.com/cskozlowski/mmu2

patakopecek

I think it would be possible to do everything (even the checking with the finda) via the duex board, David suggested to set up the finda for a dummy axis that would try to home while moving the E and the dummy axis at the same time, that would be for the FINDA part, the macros would handle the filament switching part but the only problem I could find is the filament cutting part, it is not possible to assign macros to the stall detection, so the cutting could not be triggered

dc42

@patakopecek, supporting macro execution on stall detection is under consideration for a future firmware revision.

gavatron3000

the problem ive found when trying to home to endstop/pinda is if it doesnt reach the sensor it just carrys on with the rest of the macro, if there was a feature to home to endstop but if not reached by Xmm or Xseconds then pause or retry. but this may be leaning towards conditional gcode

ive got a home built MMU2 unit hooked upto the duex2 now, just testing at this stage

dc42

@gavatron3000 said in Multi color printing with Prusa's MMU V2 & Duet?:

the problem ive found when trying to home to endstop/pinda is if it doesnt reach the sensor it just carrys on with the rest of the macro, if there was a feature to home to endstop but if not reached by Xmm or Xseconds then pause or retry. but this may be leaning towards conditional gcode

If it doesn't reach the endstop, then I presume either the amount of movement specified in your G1 S1 command is too low, or you are using G1 S1 without selecting relative coordinates first, or your axis is getting stuck. The first two are easily fixed, the last is mechanical

gavatron3000

Yes exactly, the drama is with relation to the mmu2 is if there is a jam during loading the firmware isn't able to detect this until perhaps the filament sensor is reenabled just before printing with a new tool
This also applies when unloading too
I guess though it still picks up the error eventually, I'll try jigging the macro's differently by enabling the filament sensor at different points see what outcomes occur during tool changes

Just thinking out aloud here, don't mind me

gavatron3000

Hi all, id thought id report back to say running the mmu2 with the duet and duex is possible and working even with loading and unloading detection using the "finda" style setup. its all working as expected now i just need to dial my ramming settings to get good tips. if anyone has any questions let me know. but its a win

my next thing is to setup filament-change.g to unload filament through the front of the mmu