Please help. Z Axis no longer Homes after random crash



  • Hi all, first post on the Duet forum. I'm hoping someone can help solve my problem. I recently upgraded my cnc with the Duet WiFi controller and, for the last three weeks it has been working as expected, without any issues. However: yesterday, after sucessfully completing several operations, I uploaded my final, fairly basic 3D Parallel operation (all created in Autodesk Fusion 360). The machine took an un-expected trajectory to the Work Zero position, ploughing deep into the spoil board and destroying my workpiece. Web Controls Emegency Stop did not respond in a particularly timely manner and by the time it did, it was way too late. So here I am, looking for help and advice on resolving the issues that I have. I have checked/simulated the G-Code I uploaded and there doesn't seem to be an issue with it. Here is the most worrying thing though: Now, when I hit either Home Z or Home XYZ the Z Axis does not home. It operates in the Negative direction only i.e. the Z carriage drops approximately 3mm at a time (each time the Home Z button is pressed). Both X and Y axes operate as expected when using Home XYZ. In addition when I power up the Duet, I only see active red lights on the X and Y axes. The Z Axis light is not on at all. I could use all the help I can get as I'm relatively new to cnc and only about 4 weeks into upgrading to the new controller. Sorry for the long post. Thanks in advance.



  • Please post your config.g and your homing files.



  • Please let me know if these are all that you need. I have included customconfig.g. As I understand, settings in this file override config.g. Thanks for responding.

    homez.g homey.g homex.g homeall.g customconfig.g config.g



  • whats the output of m119?



  • I have the Micro SD card in my laptop right now. It may take me some time to output the result of M119. Hang on whilst I try 🙂



  • X: at max stop, Y: at max stop, Z: at max stop, Z probe: not stopped



  • check the wiring of the endstops. unless they are triggering them at the moment they should show not stopped.



  • I have just moved the axes off the Home position X and Y are not stopped, Z is at max stop:
    Capture M119 #2.PNG



  • Did something get bent or damaged on your Z axis that is preventing it from travelling in both directions?

    If you use G92 Z10 to set the position of the Z axis while it's in a safe location are you able to manually jog the Z axis both up and down?



  • z showing triggerd all the time would explain why you cant home z.

    check the wiring of the endstop with a multimeter.



  • @Phaedrux yes, I can jog in both directions



  • @Veti showing my stupidity here but how should the multimeter respond if the switch is no good/good? Thanks 🙂



  • If you measure for continuity on opposite sides of the switch it should have no continuity if the switch isn't depressed. But it would seem that it has failed as a closed circuit, so your test would show continuity even though the switch isn't being pressed.



  • depends on the switch type.

    set multimeter to ohm.
    connect red and black probe to wires with signal and ground of the endstop

    Normaly open switch.
    infinite when not triggerd.
    some value close to 0 when triggered

    Normally closed switch
    some value close to 0 when nottriggered
    infinite when triggerd.



  • @Phaedrux Ok, thanks! I'll do this as soon as I can and let you know what results I get (most likely tomorrow).



  • @Veti Thanks. I'll let you know how I get on.



  • Ok, so I tested all three limit switches with a multimeter this evening. On both the X and Y switches I get a constant value of 1 when the switches are triggered/depressed. When I release them, I get a variable reading much closer to zero. When I test the Z switch - regardless of whether the switch is open or triggered - the value is a constant 1. Does this indicate that the Z limit switch has failed? I presume so but I have very little/no experience with this kind of thing 😄 The guys who supplied my cnc are shipping out a replacement anyway.



  • @Bags said in Please help. Z Axis no longer Homes after random crash:

    Does this indicate that the Z limit switch has failed?

    it could be the switch has failed, or the wiring to the switch.
    see if you can connect the probes to some exposed metal on the endstop itself where the wires go in and test again



  • @Veti Thanks. I will try although it is fixed in an extremely difficult place to access.



  • @Bags
    well you have to take it out anyway to replace it if its broken.
    this might give you a chance to fix it yourself and be ready before the replacement arrives.


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