Using external and internal drivers together



  • Re: DIY 3D Printer with duet wifi

    Reading another post it appears that this is a feasible solution. We have a project prototype here that will need 9 drivers total including several extruders. The question is in using a duet WiFi with the duex5 the thought is that the extruders can remain on the internal drivers using standard steppers and the axis can be run using external steppers as the size and current drawn would exceed internal drivers turning ball screws. We intend to use closed loop steppers despite the board itself is not closed loop for positional feedback and higher accuracy between motor and driver. Most are familiar with these products and that they connect to any standard open loop motion board. Using an external heat bed so we only need to switch an SSR for controlling temps. SSR is rated at 3-32v input and 120v switching for a 1300watt aluminum heat bed. Since this is not an open source project we’re doing I cannot elaborate much more about it here in the forums however the concern was the ability to relabel internal drivers from external drivers in the software so there isn’t any conflict. I presume like smoothieboard this is ok? Finding a control board to use these intended features in a 32 bit control has been daunting. While seeking an industrial solution we had no luck finding anything beyond Avante though there is no support forums or contact that can collaborate with us through development. If anyone here is affiliated with duet3d and interested in working with our company please consider contacting me for further discussion we would love to know more about the product, add on solutions, etc.. as well if our intended use is not just feasible but complete with commeircial level performance. Thank you for your time and any responses.


  • administrators

    @toysrfun it's definitely possible to use external drivers for the XYZ axis and then use the internal drivers for extruders. The only limitation is it not possible just now to mix internal an external drivers on the same axis (so for example if you use two independent stepper drivers for Z then they should both be internal or external).

    In your case with 9 drivers required in total and 3 being axis the easiest way is to use the Duet + Duet 2 so you get 7 internal drivers and then headers to connect to for 3 external drivers on the Duex2


  • administrators

    As Tony says, you can use the internal drivers for extruders and external drivers for axes. See https://duet3d.dozuki.com/Wiki/Gcode?revisionid=HEAD#Section_M584_Set_drive_mapping.

    If you do go the Duet+DueX2 route, you may need to level-shift the signals for the external drivers to 5V. One possibility would be to connect both a DueX2 and the external stepper driver breakout board to the Duet, using a 50-way ribbon cable with 3 connectors on it. I don't think this has been done before, but I can't see any reason why it wouldn't work. On the external driver breakout board you would avoid using the 2 motor hannels that are used by the DueX2.

    HTH David


 

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