Fanuc 0T-A Z axis run away on power up


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Thread: Fanuc 0T-A Z axis run away on power up

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    Default Fanuc 0T-A Z axis run away on power up

    I have a Simco HL-320 with a Fanuc 0T-A and when I press the power button a second time to power up everything the Z axis moves in the -Z direction as long as I hold the button. The hydraulic pump also comes on as long as I hold the button. It all stops when I release the button. I do not think the axis should move and the hydraulic pump should stay on. Any ideas where I should start looking?

    I've checked all my fuses. Could a bad encoder cable cause the axis to run away on power up?

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    Quote Originally Posted by forhire View Post
    I have a Simco HL-320 with a Fanuc 0T-A and when I press the power button a second time to power up everything the Z axis moves in the -Z direction as long as I hold the button. The hydraulic pump also comes on as long as I hold the button. It all stops when I release the button. I do not think the axis should move and the hydraulic pump should stay on. Any ideas where I should start looking?

    I've checked all my fuses. Could a bad encoder cable cause the axis to run away on power up?
    no,your solution it is easy,look for the Z+ hard limit switch that i think it is stucked,should be near the end of the Z+ direction,it is a limit switch.



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    Default Re: Fanuc 0T-A Z axis run away on power up

    Quote Originally Posted by zavateandu View Post
    no,your solution it is easy,look for the Z+ hard limit switch that i think it is stucked,should be near the end of the Z+ direction,it is a limit switch.
    Limit switches were definitely bad/intermittent. I cleaned the +Z and the axis stopped running away. I ordered new switch internals as the contacts looked pretty worn.

    It's still not latching the hydraulic pump as expected so I suspect I still have another issue. I cannot jog or home either axis. Any thoughts?



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    Default Re: Fanuc 0T-A Z axis run away on power up

    Is it phased correctly as may be problem if not it will be one of your limit switches



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    Default Re: Fanuc 0T-A Z axis run away on power up

    Quote Originally Posted by mbservice View Post
    Is it phased correctly as may be problem if not it will be one of your limit switches
    The phase is correct, at least for the pump I checked. The pump that isn't latching on is external so it's possible it's reversed. I'll check that.

    After I cleaned the switches I'm still not seeing one of my limits at the honda connector so I'm hunting a bad cable. Hopefully once I get the limits sorted it will start up correctly. My schematic is very hard to read so it's taking longer than expected to trace the thing out. I think I need to energize the 24V circuit and start checking with a test light.



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Fanuc 0T-A Z axis run away on power up

Fanuc 0T-A Z axis run away on power up