Drive mapping not quite working for mixing extruder setup



  • Hi there again. Another unusual setup. I am building a delta ceramic printer using extrusion components sourced from Cerambot.

    This printer uses a Nema 23 piston-powered main clay reservoir and a Nema 17 driven auger extruder. I've got everything working, except that the Nema 17 auger extruder is not functioning (connected to the Duet wifi E0 internal stepper driver). Big stepper external driver is connected using step/dir/enable via E3 on the expansion header.

    Board: RepRapFirmware for Duet 2 WiFi/Ethernet version 2.05 running on Duet WiFi 1.02 or later

    In my config file drive mapping section, P5 is the external stepper driver to the Nema 23 piston extruder and that's working great. Nema 17 motor P3 is the auger, connected to the E0 stepper driver output.

    ; Drives
    M569 P0 S0 ; physical drive 0 goes forwards
    M569 P1 S0 ; physical drive 1 goes forwards
    M569 P2 S0 ; physical drive 2 goes forwards
    M569 P3 S1 ; physical drive 3 goes forwards (Nema 17)
    M569 P5 S1 T2.5:2.5:5:2 ; physical drive 5 goes forwards (External, Nema 23)
    M584 X0 Y1 Z2 E3:5 ; set drive mapping
    M350 X16 Y16 Z16 E16:16 I1 ; configure microstepping with interpolation
    M92 X200.00 Y200.00 Z200.00 E663.00:663.00 ; set steps per mm
    M566 X600.00 Y600.00 Z600.00 E1200.00:1200.00 ; set maximum instantaneous speed changes (mm/min)
    M203 X12000.00 Y12000.00 Z12000.00 E1200.00:1200.00 ; set maximum speeds (mm/min)
    M201 X500.00 Y500.00 Z500.00 E1000.00:1000.00 ; set accelerations (mm/s^2)
    M906 X1700 Y1700 Z1700 E800:800 I60 ; set motor currents (mA) and motor idle factor in per cent
    M84 S30 ; Set idle timeout

    ; Tools
    M563 P0 S"Clay" D0:1 F0 ; define tool 0
    G10 P0 X0 Y0 Z0 ; set tool 0 axis offsets
    G10 P0 R0 S0 ; set initial tool 0 active and standby temperatures to 0C
    M568 P0 S1 ; enable mixing for tool 0
    M567 P0 E0.5:0.5 ; set mixing ratios for tool 0
    ;M302 P1 ; Allow cold extrusion
    T0



  • Most external drivers need a longer pulse width than Duet default. See doc for M569.



  • @Danal said in Drive mapping not quite working for mixing extruder setup:

    Most external drivers need a longer pulse width than Duet default. See doc for M569.

    Of the two, the external driver is the one that's working though.



  • Ahhh... interesting.

    I see you commented out the cold extrusion... that was my first thought.



  • What is a typical G0 or G1 command that would move the auger extruder?



  • Is it allowed to skip the second board driver E1 in the mapping?

    Danal, because of the way the 'Tool' is set up as mixing, it is treated like any extruder extrusion command the firmware does the mixing based on the M567 ratio.

    But, this is my first attempt at a mixing extruder, so I've almost certainly fat-fingered something?


  • administrators

    I don't see anything wrong with your config, except that a mix ratio of 1:1 would make more sense than 0.5:0.5. I suggest you check the wiring to the extruder motor.



  • Ok, I resolved the issue by moving the E0 stepper to E1 connector and making the change for that stepper output 3 to 4 in the config.g file.

    M569 P4 S1 ; physical drive 4 goes forwards
    M569 P5 S1 T2.5:2.5:5:2 ; physical drive 5 goes forwards
    M584 X0 Y1 Z2 E4:5 ; set drive mapping

    It appears that you can skip a stepper driver P3 after defining the xyz motion steppers, but the extruder mixing stepper drivers have to sequential? E4:E5


  • administrators

    No, they don't have to be sequential.



  • @dc42 Well.... 🤷 No worries. I'm just happy to get it working and to move on to my next issue, which is to figure out exactly how many steps/mm this big stepper puppy needs and what the actual mix ratio is supposed to be. The Cerambot documentation is thin, to put it kindly.

    Thanks again for a really fantastic piece of configurable hardware.

    Steve Graber


  • administrators

    It could mean that the E0 driver is faulty, in which case you might want to ask for a replacement while the board is in warranty.


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