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IndustryArena Forum > Machine Controllers Software and Solutions > Fanuc > Fanuc 0T-A Z axis run away on power up
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  1. #1
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    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?

  2. #2
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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.

  3. #3
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    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?

  4. #4
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    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

  5. #5
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    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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    Re: Fanuc 0T-A Z axis run away on power up

    I spoke with Danobat-Marathon in Texas, who has been very helpful in sourcing spares for this old machine, and they indicated that the DC drives have to be adjusted using a battery whenever anything changes. I've been waiting for the instructions. I did swap out the Z axis drive for a spare I had rebuilt and replaced the flaky limit switch. It no longer runs away but I'm still not able to get the drives to indicate ready. Press power button, pumps come on, and then 401 SERVO ALARM: (VRDY OFF). I did manage to find a manual in Russian for the drives. The drives are Stromag CVT 025.4. The lathe was sold in the EU as the EEN-320. At least now I know what the lights mean. Tomorrow I'll try again and see if I can catch which lights come on the drives.

    Does anyone know how to adjust DC drives using the battery method?

  7. #7
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    Re: Fanuc 0T-A Z axis run away on power up

    did u have on the operator door a double check closing limit switch?
    check that if u have

  8. #8
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    Re: Fanuc 0T-A Z axis run away on power up

    It has been a few months. I've been busy on other projects. I did get a schematic of the battery test box and built it a couple months ago but never got around using it. Today I used it to validate the drives and I was able to home the X axis. I figured I'd upload the schematic as it may help others. Now that I understand the process, I likely could have done most of the testing without building the box.

    Now I just need to sort out the limit and reference switches once and for all. I've attached the schematic. If I'm looking at this correctly XT10-017 should supply +24V from the control DC power supply through the limit and reference switches. Any suggestions for testing them? Test light at the Honda connector? What is the best place to ground the test light when probing for +24V?

    I have replaced all of the Z axis limit switches already. One of them was flakey. Unfortunately it didn't sort the issue. zavateandu, I'm certain you nailed it originally. I just need to find the bad connection.

  9. #9
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    Re: Fanuc 0T-A Z axis run away on power up

    I made a little progress but still can't get the Z axis to home. I found if I remove connection 16 on the Stromag Z axis drive the machine will latch on and allow me to jog/home the X axis, open/close the chuck, start/stop the coolant pump, and it's running the oiler. I was able to verify a lot of stuff.

    It will not work if I simply remove the axis drive entirely. Interestingly, connection 16 on both drives are daisy chained together. The manual states this is the release/deblocking connection (translated from Russian). If I touch the blue wire to 16 on the Z axis, the machine instantly delatches. When I measured the voltage on 16 and 17 on the Z axis I read 15V. I read zero volts on the X axis. I guess now I need to discover what can cause the axis drive to release. The lights indicate both are enabled. When I swap the axis drives the behavior is the same, it doesn't follow the drive.

    My guess at this point is that the controller is signaling a stop condition to the drive. I'm back to limits... again. Is there a way to look at the limit states on the controller? I've been checking everything I can with the test light but maybe I have a bad connection at one of the Honda connectors.

    The best I've been able to glean from the Russian manual with German schematics is:
    1 & 2 setpoint input 1 (translated from Russian)
    16 & 17 Release/Deblocking
    21 & 22 Ready/Operational (betriebsbereit in German on schematic)
    Attached Thumbnails Attached Thumbnails IMG_4110.jpg   IMG_4111.jpg  
    Attached Files Attached Files

  10. #10
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    Re: Fanuc 0T-A Z axis run away on power up

    Way Lube Oil Tank is low?. I've seen some machines lockout Z movement if, a low level condition triggered.

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

    Quote Originally Posted by machinehop5 View Post
    Way Lube Oil Tank is low?. I've seen some machines lockout Z movement if, a low level condition triggered.
    Good thought. Fluids are all topped up. I'll check the float signals tomorrow. I can see way lube moving. I don't see any flags in DGNOS 0700, 0701, or 0712, but the manual clearly states that not all switches are present in the DGNOS.

    Maybe if I can find the Fanuc signal pinout for the Honda connectors M2 & M4 I might have a better idea of what the axis drives are expecting. I don't see any voltages on 1 & 2 or 21 & 22 on either axis so I'm not sure what the signal from the velocity controller might be. Maybe I'll hook up the scope tomorrow and see what I can find.

    Is it possible to swap the axis Honda connectors and test the Z axis as X?

  12. #12
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    Re: Fanuc 0T-A Z axis run away on power up

    Quote Originally Posted by machinehop5 View Post
    Way Lube Oil Tank is low?. I've seen some machines lockout Z movement if, a low level condition triggered.
    I checked all the fluids. Spindle was a little low but still above the float. Traced out a few more things but it still won't clear.

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