What is the Maximum # of Stepper Drivers for Duet 2 & 3?

  • Quick question I couldn't find a quick answer to . . .

    Assuming I'm willing to use Duet expansion boards But do not want to use external (non-Duet) stepper drivers, what is the maximum number of stepper drivers one could reach with the Duet 2 and the Duet 3?

    I'm assuming the Duet 2 would max out at 10 (5 on the Duet 2 + 5 on the Duex5 expansion board)

    My understanding is that the Duet 3 can total more than this, apparently by having more than one expansion board, but I am curious what the maximum would be.

    Thanks for any insight, and apologies if this is already posted and I missed it.

  • @tom_lauerman You are right about Duet 2 - 5+5 on board drivers. On Duet 3 the main board has 6 stepper drivers and (ignoring the single driver tool board), the current expansion board has 3 stepper drivers. These expansion boards can be daisy changed. I don't know for sure how many can be linked but each board has a 4 pole DIP switch to set it's address. So in theory you could add 15 expansion boards giving a total of (15x3+6) 51 stepper drivers. On a slightly more practical note, I run 3 expansion boards but two of the drivers on the main boards aren't used so I'm only using 13 of the available 15. That's a CoreXYUVAB (plus Z) with 6 extruders.

  • @deckingman Fantastic information, and prompt as always.

    I was asked what the maximum number of tools I could have on my clay printer would be and I wanted to entertain the hypothetical (no plans to pursue this presently).

    So in my case there needs to be:
    1 X axis stepper
    1 Y axis stepper
    3 steppers per tool (1 for a Z axis, 1 for syringe "feed", 1 for auger)

    51 - 2 (X & Y) = 49

    49 divided by 3 (per tool) = 16.333

    So it seems like 16 tools would be the maximum for my design. There would be absolutely no good reason to pursue this . . .

    . . . and yet sometimes its hard not to daydream about these hypotheticals.

  • administrators

    Actually the latest expansion board firmware allows the address switches to be overridden, so you could in theory have 125 expansion boards. I'm sure that loading on the CAN bus would be a problem long before that. But there is also a second CAN bus on the Duet 3 main board.

  • @dc42 OK, thanks for this. I guess I'll go put 125 expansion boards in my shopping cart (joking). Fascinating to know there is more or less unlimited capacity with Duet 3.

  • @tom_lauerman said in What is the Maximum # of Stepper Drivers for Duet 2 & 3?:

    Duet 3 can total more than this, apparently by having more than one expansion board

    Fun discussion of theory above... in physical reality, I have a Duet 3 6HC, six drivers, and two 3HC expansions, 3 each, total 12. Already beyond Duet 2 + Duex5 limit of 10. The chained expansions work flawlessly.

    This is on a tool changing printer; it is possible I'll go even further in a single printer, as I want to drive some movement of a camera and a probe that assist with tool-to-tool alignment.

    I'm also confident that there are others with even larger, currently deployed, real world implementations.

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