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Thread: FANUC 18i-WA unable to reference machine zero on U-axis

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    Default FANUC 18i-WA unable to reference machine zero on U-axis

    We have a Charmilles Robofil 330F wire edm with a FANUC 18i-WA control. Recently our shop experienced some power problems causing the lights to flicker. This caused the wire EDM to shut down during a critical burn. When I powered on, all axis required a reference return. When I did an automatic return, the U-axis traveled past the soft limit to the end of the ballscrew causing a hard 507 -overtravel alarm.
    I referenced all the other axis and manually jogged the U-axis to a safe position close to where it should reference home. Reset Keep Relay (K01, bit 6) per Charmilles and powered down. Powered on while holding <Delete> key to zero all axis on position screen. I jogged all axis away from home and did a reference one axis at a time with the U axis being last. It again traveled past the zero on machine position screen, so I quickly hit reset to stop movement.

    How can I reset the zero reference position? It is a dogless reference with soft overtravels, linear scales on all axis. FANUC 18i manual has a procedure using parameter 1002 and 1005, but my control doesn't have PRM 1002. Goes from 1001 to 1003.

    I appreciate any help!


    Greg
    Last edited by GregR; 09-17-11 at 09:19 AM.

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    Default Re: FANUC 18i-WA unable to reference machine zero on U-axis

    Hi my friend i thought you should check parameter 1815 apc and apz and than 1320-21-22... (+)(-)limit parameter if the axis lost position you have to introduce reference
    how do you do that

    1-) Look axis's body for any sign if you can see sign zoom them each other
    if you cant see any sign movie the axis where you want reference point

    2-)Take mode mdi. and open pwe.

    3-)Find parameter 1815

    4-)Change the apc 0 for u axis and than

    5-)Press emg.

    6-)Turn off the machine

    7-)Turn open it again

    8-) Come again 1815 u axis apc

    9-)Change it with 1

    10-)Turn off and turn open

    IT IS OKAY

    but before everything try first one open the machine with p and can from keyboard.

  3. The Following User Says Thank You to musti For This Useful Post:

    GregR (09-19-11)

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    Default Re: FANUC 18i-WA unable to reference machine zero on U-axis

    Thanks for the info, musti

    I was able to get it running again over the weekend. I found that setting a 1 in the APZ bit of that axis on 1815 caused a zero point reset. From there I was able to tweak the position enough to be able to go through a vertical reference cycle. It is burning fine now, although I'm assuming that what I did was just a quick fix/bandage to the real problem. I haven't tried to reference home position since.

    I will go through the process you described before I set up the next job and let you know how it worked.

    Thanks again!

    Greg

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    Default Re: FANUC 18i-WA unable to reference machine zero on U-axis

    Resetting APZ on param 1815 works while the power is on.

    Did a complete machine power off, minute wait, power on, reboot -- still unable to reference home on 3rd axis. But resetting that parameter gets things going again.

    Since I set all axis to zero at home position, I just jog that axis to zero and reset the APZ bit again. I rarely power down so it's not a big issue, but I would like to try to fix it eventually.

    Willing to try other suggestions.

    Thanks!


    Greg

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    Default Re: FANUC 18i-WA unable to reference machine zero on U-axis

    If you are using the APZ bit then you have absolute encoders and the machine should not have to be referenced at powerup.

    Stevo
    (The opinions in this post are my own and not those of machinetoolhelp.com and its management)

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    Default Re: FANUC 18i-WA unable to reference machine zero on U-axis

    IIRC when you are using the APZ bit then you have absolute encoders and the machine should not have to be referenced at powerup.

    Stevo
    (The opinions in this post are my own and not those of machinetoolhelp.com and its management)

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    Default Re: FANUC 18i-WA unable to reference machine zero on U-axis

    Yes. I need to clarify more. 99% of the time when I power off, the machine remembers position. Every now and then all axis flash red after a reboot, but I rarely power down. The problem is that when I tested the reference position after resetting APZ, the 3rd axis will not return. I then have to manually jog/step to zero and reset the bit again. It runs fine after that as long as I don't shut down the machine.

    I'm just curious about what may have happened during the power brown-out. It's not recognizing the soft limits on that axis either even though the parameters are set correctly.

    I do believe that the main contactor relay and protection diode need to be replaced because of a low voltage alarm I got a few months ago. Did a thermal scan of the transformer and the entire electrical cab... transformer was fine - voltage normal. The relay was warm in the coil pack area. Right now the various voltages are checking within range so I'm going to keep running.

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    Default Re: FANUC 18i-WA unable to reference machine zero on U-axis

    yes stevo you all right but if 3rd's servo driver's battery low it can forget the position

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    Question Re: FANUC 18i-WA unable to reference machine zero on U-axis

    Hello all,

    Did you get alarm 300 "APC alarm" after power on? This is normal with Fanuc if using absolute encoders and battery failure, has resulted in loss of axis reference.

    If so: locate the batery pack for the U axis servo drive and remove - (ONLY WITH POWER ON TO CNC) and exchange for new.

    Then it is possible to set absolute pulse coder (APC) to 1 after establishing reference position mentioned earlier in this post. The APZ bit - when set to 1 - means that the axis is referenced!!

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    Default Re: FANUC 18i-WA unable to reference machine zero on U-axis

    If you are still getting the "soft" overtravel alarm then you may have not set the zero position "exactly" to where it was before the loss of position. If all of your batteries are fine then you will probably have to adjust the soft limit parameters. FYI these parameters are usually set 3mm past reference position that is why it is very easy to think you set it in the same spot but it only takes a bit to be off.

    If you have absolute parameters why are needing to reference the U-axis at powerup??

    Stevo
    (The opinions in this post are my own and not those of machinetoolhelp.com and its management)

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    Default Re: FANUC 18i-WA unable to reference machine zero on U-axis

    Normally I don't have to reference anything at power up, but occasionally(rarely) the machine needs a reference before I can even jog an axis. Makes me think that I should replace the main contactor relay and protection diode (12 years old). Power surging at start up? Variations in voltage? Contacts worn/misaligned?? I don't know. I've seen electronics do some strange things with 'unclean' power. I Have a new relay here and will replace it anyway during the next slowdown of workflow.

    The U-axis does not recognize the "soft" limits. If I let it travel past where they are set, it will go to the end of the ballscrew and give a 507 alarm. Not good. So I guess the next step would be replacing the battery. All parameters appear to be set correctly for this axis.

    I'm scratching my head over this one. But at least the machine will run normally for now.


    Greg

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    Default Re: FANUC 18i-WA unable to reference machine zero on U-axis

    I forgot to add that I don't know exactly where the axis reference point was prior to the issues I'm having. So you're probably right, Stevo. I'm sure I reset the zero point in a different spot. I'll check the "soft" limit location and see where the home reference point is compared to that.

    Thanks!


    Greg

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    Default Re: FANUC 18i-WA unable to reference machine zero on U-axis

    Let us know what you come up with.

    Stevo
    (The opinions in this post are my own and not those of machinetoolhelp.com and its management)

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    Default Re: FANUC 18i-WA unable to reference machine zero on U-axis

    I recently had a FANUC pro in the shop for some other maintenance issues. He looked at the machine and told me that it is referencing position from the glass scales only -- 1815.1 is set to 1 for all axis. 1815.5 is zero on all axis. (this is not the info the mfgr. gave me during a service call)

    The U and X axis use the same scale.

    He asked if I was comfortable with manually resetting the U-axis home position if the machine needed a reference. I told him that I was since it is rare that the machine needs to reference home. So that was the end of that.

    I did some searching for the soft limits and found that in PRM 1321 (LIMIT -1) the X limit is set to -26266 and the U limit is -26233. Since the U axis travels farther than the X position in both + and - directions (for taper cutting), shouldn't the U axis limit be bigger than the X limit? Maybe -26366? When the machine references home, Z is first followed by X, U, Y, V in that order. Home position is front/left (-x/-y)

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