Need ideas/help with Z homing 2 independent Z motors



  • Hi everyone,
    I'm a little stuck on configuring my custom CoreXY HEVO I'm using dual motor's for the Z, one attached to Z and the other attached to E1. I've read through a number of other peoples configurations using dual Z motors on the forum but I'm still stumped. I'm using a NPN normally open Z probe sensor for the Z axis, I've done a static test with my Z-probe and the web interface shows my Z probe working correctly. When I try to do a dynamic test using the G30 command the bed moves in the wrong direction, away from the hot end. Once I trigger the Z probe it then moves back in the correct direction a small amount and stops. When I try to home the Z axis the bed doesn't stop when the Z probe sensor is triggered and it runs into the hot end. I'm sure I have something configured incorrectly I know I probably need to adjust the lead screw positions slightly in the config.g m671 command, but I don't see how that would produce the incorrect movement direction. After I do a dynamic test manually triggering the Z probe I am able to jog the motors and they move in the correct direction. I know it must be something small that I'm missing in the configuration.

    Any ideas? They would be greatly appreciated, thanks.

    Using Duet Ethernet 1.02 or later
    Firmware 2.0(RTOS) (2018-06-05b3)
    Web Interface Version: 1.21.1
    CoreXY HyperCube Evolution

    3_1565505289709_homez.g
    2_1565505289709_homeall.g
    1_1565505289709_config.g
    0_1565505289708_bed.g


  • administrators

    @pibbs said in Need ideas/help with Z homing 2 independent Z motors:

    When I try to do a dynamic test using the G30 command the bed moves in the wrong direction, away from the hot end. Once I trigger the Z probe it then moves back in the correct direction a small amount and stops.

    It sounds to me that either your Z axis is moving in the wrong direction always, or the probing speed is set too high. +Z motion should raise the print head or lower the bed, so that the distance between nozzle and bed increases. Is that what happens?



  • M584 X0 Y1 Z2:4 ; two Z motors connected to driver outputs Z and E1

    You are missing the E assignment. See the big warning in https://duet3d.dozuki.com/Wiki/Gcode#Section_M584_Set_drive_mapping
    Your e1 is currently both an extruder and a z driver

    M305 P0 T100000 B4138 R4700 ; Set thermistor + ADC parameters for heater 0
    M305 P1 T100000 B4138 R4700 ; Set thermistor + ADC parameters for heater 1

    4138 is the default and most certainly wrong. this is unrelated but will cause temperature inaccuracies.



  • @dc42 Yes the bed lowers increasing the distance between the nozzle and bed, it sounds like this is the correct response to sending a G30? It makes me think you might be right that I have my Z axis moving in the wrong direction.. jogging + should increase the distance between the nozzle and bed? It's currently reducing the distance between nozzle and the bed.

    @Veti Thanks for catching that you are correct I haven't changed e1 from being assigned as an extruder. I'm sure you just saved me some headaches down the road.



  • I don't know if it's relevant but you have 3 M208 entries...a single ones up top that does the min and max for x and y in one in one shot and then the other 2 under axis limits.



  • @pibbs said in Need ideas/help with Z homing 2 independent Z motors:

    Firmware 2.0(RTOS) (2018-06-05b3)
    Web Interface Version: 1.21.1

    Probably time to update the firmwares.



  • @phaedrux Thanks, your completely right I didn't realize how out of date my firmware was. I've updated it to the most recent versions we will see if that changes any of the behavior.

    Firmware Version: 2.04RC1 (2019-07-14b1)
    Web Interface Version: 1.22.6



  • Thanks everyone for all your help I now have my Z homing correctly! Not sure if it was partly an issue with the older firmware. I also had my 586 configured incorrectly and my motor's where moving backwards.

    I have one more question regarding my Z homing after it homes it drops the bed down to far by a few MM do I need to go into the negative numbers with my G31 P500 X0 Y0 Z0 command? should it be Z-1 or is this set somewhere else I'm missing?



  • Z-1 would mean that the probe triggers 1mm after your nozzle hits the bed.
    This is normal not what you want.

    if you want the bed to go closer to the nozzle you have to increase the distance in the positive.



  • @veti thanks again makes total sense, I appreciate the quick response.


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