Duet 3 Mainboard 6HC & Duet 3 Expansion 3HC



  • Hi all,

    Looking for a check on my thinking after reading a bit of the documentation.

    I currently have a Duet 3 Mainboard 6HC with X, Y, Z, U, E0 and E1. I use two Z motor on one driver and this work OK, However the bed on my printer is heavy and when I power off the printer the bed drops, this isn't always the same amount on both lead screws and this results in a tilted bed.

    I would like to therefore to give each motor and lead screw it's own driver, however after reading the documentation am I to understand that it's not possible to use Z motors on the Duet 3 Expansion 3HC?

    The Duet 3 firmware configuration limitations document seems to contradicted itself by first saying:

    • Z probes connected to expansion or tool boards are limited to types 8 and 9." and then.

    Then saying:

    • Endstop switches and Z probes connected to the main board cannot control motors on an expansion board. This is planned to be fixed in release 3.4.

    • If you use a Z probe then the Z motors must be connected to the main board. This is planned to be fixed in release 3.4.

    Would I be better moving the extruders to the Duet 3 Expansion 3HC but then I understand PID tuning is an issue?

    What other options do I have?

    Thanks.


  • administrators

    @Rushmere3D said in Duet 3 Mainboard 6HC & Duet 3 Expansion 3HC:

    Would I be better moving the extruders to the Duet 3 Expansion 3HC

    That is my recommendation, move the extruders to a 3HC or to two tool boards. The limitation on where Z motors are connected may not be removed until RRF 3.4.

    but then I understand PID tuning is an issue?

    Automatic heater model tuning is supported in RRF 3.3beta. Heater model tuning can be done manually in earlier versions (basically, you do exactly what the RRF 3.1.1 and earlier auto tuner would do).



  • @Rushmere3D Another work around for the heater tuning is to temporarily extend the heater and thermistor wires so that you can connect them to the main board (and change the configuration file to suit). Then do the heater tuning, then swap things back to the expansion board. If you only have one hot end, you only need to do that once. (If you are trying to develop a hot end and keep changing the design, then it becomes real pain).



  • @dc42 Thanks DC42, so am I right in thinking if I use the expansion board for the extruders all connections associated with them also need to move so, motors obviously but heaters and thermistors too. What about fans, both hot end and part cooling?

    Thanks.



  • @deckingman Thanks, if I have already PID tuned the hotends before adding an expansion board I can just use that data, right?


  • administrators

    @Rushmere3D said in Duet 3 Mainboard 6HC & Duet 3 Expansion 3HC:

    @deckingman Thanks, if I have already PID tuned the hotends before adding an expansion board I can just use that data, right?

    Yes.



  • @dc42 Thanks and what about my other enquiry above?

    Regards, J.


  • administrators

    @Rushmere3D said in Duet 3 Mainboard 6HC & Duet 3 Expansion 3HC:

    @dc42 Thanks DC42, so am I right in thinking if I use the expansion board for the extruders all connections associated with them also need to move so, motors obviously but heaters and thermistors too. What about fans, both hot end and part cooling?

    Thanks.

    You don't have to move everything, but there are some limitations documented at https://duet3d.dozuki.com/Wiki/Duet_3_firmware_configuration_limitations. The main ones relating to extruders are:

    • The hot end heater and hot end thermistor must be connected to the same board (so both connected to the main board, or both connected to the expansion board)
    • If you use a filament monitor than it must be connected to the same board as the extruder motor


  • @dc42 Thanks.



  • @Rushmere3D said in Duet 3 Mainboard 6HC & Duet 3 Expansion 3HC:

    @deckingman Thanks, if I have already PID tuned the hotends before adding an expansion board I can just use that data, right?

    As @dc42 said, yes of course you can. One little tip, if you haven't already tuned the heaters with the latest algorithm (i.e. post RRF3.2) then you might want to do that before connecting the heaters and thermistor to an expansion board (but you can still use the old style PID parameters so it's not all that important).


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