RFI about weird dual extrusion setup



  • I designed and built an i3 style printer a while ago. It currently has a single-nozzle-dual-extruder bowden setup. Recently, a NEMA 11 stepper fell in my lap, and I had the idea of adding a geared extruder on the print head that the two bowden extruders could feed into (one at a time, of course).

    My question is, what would be required for this to work, firmware and electronics wise? I'm running a duet maestro, which only has two extruder drivers, so I would likely need an expansion board. But I would also need to have each of the two bowden extruders assigned to a different tool, with the geared direct-drive extruder controlled by both. Is this possible with the current firmware?

    Thanks all!

    Edited for clarity



  • @Lukrative What you want to do is easily achievable on any Duet, not in the least with Meastro. The best setup is up to you and which slicer you use, as you can make a combined tool, individual tools, or use firmware retraction. As for the nema11 you'll find you need very high gearing and that will cost speed that would be needed for a quick change / Y splitter setup. Even nema 14s are rare in extruders. I'd guess 6-10X gearing needed. Good luck!

    The maestro natively handles two extruders.



  • @3ddevil Good to know about the anticipated gear ratio, I was a little worried about that.

    As far as the setup is concerned, would I not need three extruder drivers? One for each of the "main" bowden extruders and another for the geared direct drive? And the idea was to have two extruders pushing the filament in tandem, since it would be a little tricky to design an extruder that could disengage itself.



  • @3ddevil To clarify, the printer already has two bowden extruders feeding into the y-splitter. I am just wondering about the feasibility of adding that third geared extruder to the mix.



  • If you're already using all the stepper drivers on the Maestro, you can add up to two more via the expansion header (it's different from the Duet Wifi expansion header, which supports more). The easiest thing to use is the Maestro Dual Stepper Driver Expansion Module

    If you want to wire in your own stepper driver, use the Maestro wiring diagram and expansion module documentation to guide you for connections and configuration.

    Ian



  • @droftarts Thanks for the links! They led me to take a closer look at the gcode documentation. The M563 documentation says the following:

    "It is permissible for different tools to share some (or all) of their drives and heaters. So, for example, you can define two tools with identical hardware, but that just operate at different temperatures."

    It seems, then, that the easiest thing is to get that expansion module and define tools 0 and 1 to use the extra drive, in the same way that they already share heater 1.


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