Dual motor extruder with 1 nozzle

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Hi!
I'm looking for experience and maybe advices. I have my own design IDEX printer. I have huge problem with slicer setring to make it working for dual material printing (eg. Want to lower nozzle of second extruder after movement on a position).
So decided to swap system to 1 hotend with direct drive extruder and add some fancy Y pipe and connected to it 2 bondtech extruders. Is Duet 2 WiFi powerfull enough to run 2 extruder motors simulationusly without any issues (retraction etc same time) or do I need build ERCF?

@button I believe the Duet 2 Wifi has 5 drivers, so assuming the machine youre using has one stepper motor for each motion axis you can run two extruders just fine. If not, you would need an expansion for extra drivers.

Though I don't know if you actually mean "simultaneously" literally like mixing the filaments in the hotend. You would need a specifically designed hotend for that.

For your problem with the IDEX and for getting the 2 in 1 out setup working, if you defined each tool (hotend & extruder combination) in your firmware configuration, then defined the firmware tool change gcodes, the slicer would only have to tell the printer to switch tools and then the printer handles the tool change from running the appropriate tool change gcodes.

Check out section 8 of this
https://docs.duet3d.com/en/How_to_guides/Configuring_firmware
and this
https://docs.duet3d.com/User_manual/Tuning/Tool_changing

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@wwak84 duet with duex has 10 steppers, all in use right now.
All of tutorials from duet wiki I've done. Its slicer, not duet problem - how RRF could know when lower Z after 1st xy move after toolchange?

Simulationusly meaning spool->feeding extruder->bowden tube->direct extruder

@button I'm not sure I understand the issue.

@button said in Dual motor extruder with 1 nozzle:

Its slicer, not duet problem - how RRF could know when lower Z after 1st xy move after toolchange?

Is this referring to the IDEX or 2-in-1-out setup? For the IDEX having tool offsets defined I think would be a possible solution. For the 2-in-1 out setup, I dont see why you would need to adjust the Z ?

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@wwak84
From the begining:
You're printing with tool0, then coming T1 command from slicer - and tfree0 macro is called and tpost1. In macro tfree0 you gave eg G1 Z2 line. In tpost1 you cant gave G1 Z-2 because you'll move head down before it reach printing position in XY. Machine to move T1 head to the printing coordinates in X and Y and then lower gantry in Z. Not before. After XY movement. SuperSlicer not sending Z when you're not using wipe tower (it won't use it)

@button Does the tool change occur at the XY location where the new tool will start printing?

If so, you could define global variables for XYZ machine positions in your print start gcode, set those variables to the machine position when tool change is called, and at the end of tpost move to the saved XY position, then lower Z. Thats about all I can come up with. Hopefully someone has a better understanding of how to help with this issue. Good luck!

https://github.com/Duet3D/RepRapFirmware/wiki/Object-Model-Documentation#moveaxesmachineposition

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@wwak84
But problem is that my main question was about 2 extruders pushins same filament to 1 nozzle

Oh, and i cant tell machine where it should start prinitng because eg tool 0 was printing object 1, and tool 1 starting printing from object 3.

deckingman

@button said in Dual motor extruder with 1 nozzle:

@wwak84
But problem is that my main question was about 2 extruders pushins same filament to 1 nozzle

With regard to that specific question - yes. Dual extruders in a push-pull arrangement can be done and have been done by a number of people using Duet boards. From a hardware and firmware perspective, it's no different to having two or more extruders feeding a multi-input, single nozzle hot end. The only difference is that you configure the mixing ratio to be 1.00:1.00 rather than some other value such as 0.50:0.50.

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@deckingman
I was thinking about loosing sync between both motors and eg. building pressure in bowden tube because one motor will be going faster (steps set correctly)

deckingman

@button said in Dual motor extruder with 1 nozzle:

@deckingman
I was thinking about loosing sync between both motors and eg. building pressure in bowden tube because one motor will be going faster (steps set correctly)

Well for sure, if you set different steps per mm for each extruder, then bad things are going to happen. But if the steps per mm are set correctly for each extruder, and there is no extruder slippage, then you shouldn't have a problem.

In your opening post you asked the question " Is the Duet 2 WiFi powerful enough to run 2 extruder motors simultaneously...." and the answer is yes. But if you don't set the extruders up properly, so that they both feed at exactly the same rate, then you will have problems - that's a mechanical or tuning issue. From a Duet perspective, both the firmware and hardware are capable of doing what you want to do. But there is no easy way to compensate for mechanical or tuning errors that you might introduce when setting it up.