Y Endstop False Triggers?



  • So I have this strange glitch with my Y Endstop homing not always working. Copied and pasted below is my homey.g file (350mm Y-axis)

    G91 ; relative mode
    G1 Z2 F1800 ; raise head to avoid dragging nozzle over the bed
    G1 Y-355 F3000 S1 ; move up to 240mm in the -Y direction, stopping if the homing switch is triggered
    G1 Y3 F600 ; move slowly 4mm in the +Y direction
    G1 Y-10 S1 ; move slowly 10mm in the -Y direction, stopping at the homing switch
    G1 Z-2 F1800 ; lower the head again
    G90 ; back to absolute mode

    If the bed is already close to the Y endstop, it homes fine, but if it's finished a print or moved too far away, it moves back slightly and acts like it's triggering the endstop when it is not near home.

    My endstop is attached under the bed and the thermistor, bed heat, and endstop wiring runs together. Could there be some kind of interference causing a false trigger?

    I've been disabling the motors, pushing the bed all the way to the home position where the switch triggers and then re-homing it (which does work). I can play with settings more if anyone has suggestions.

    Update / Edit: I did this strange homey.g check using G92 to fake set Y350 and then move it back to home without relative positioning, but the false endstop trigger (or whatever seems to be happening) did the same or a similar thing.



  • Maybe your steps/mm on the Y are off and it isn't moving far enough. Try changing your second G1 to Y-400 or more and see what happens. If it works, make sure the steps are correct or the possibility that you have more travel than you think.

    One last thing would be to make sure there isn't any binding and you have the current turned up enough in your config.g.


  • administrators

    What type of Y endstop switch are you using? If it is a microswitch, are you using the NC or the NO contacts?



  • @dc42 said in Y Endstop False Triggers?:

    What type of Y endstop switch are you using? If it is a microswitch, are you using the NC or the NO contacts?

    I had an engineer build this printer, so I had to look at the switches up close and it looks like X Axis and Y Axis are both NC. I could pretty easily rewire to NO if that is recommended. The Y Axis switch is using blade terminal clamps (? guessing at the name here), so I may look at that as well, it could need a bit of solder on the actual switch.

    Is the default recommendation for NC or NO switch wiring?


  • administrators

    The recommendation is to use NC. If the endstop wires run parallel to the stepper motor wires for an appreciable distance, then either or both sets of wires should be twisted pair so that they pick up less interference.

    Have you checked that when you command 10mm of Y movement, you get 10mm? If not then your steps/mm may be incorrect as @number40fan suggested.



  • I'm thinking it must be interference. It seems to randomly trigger within ~1-2 seconds of the bed moving, but if it's close enough to the homing position, it homes in under a second and is fine.

    The switch is fixed to the bottom of the moving bed now, so I may separate it out and place it on the printer body and have it fixed so the bed bumps into the stationary switch.

    Thank you for the help, this forum is a lifeline for printer tinkering.


  • administrators

    @saffi said in Y Endstop False Triggers?:

    The switch is fixed to the bottom of the moving bed now

    Could it be a dodgy connection to the switch which sometimes breaks as the wire flexes?


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