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IndustryArena Forum > MetalWorking Machines > Okuma > LNC8 (94) control shutting off mid program
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  1. #1
    Join Date
    Sep 2016

    LNC8 (94) control shutting off mid program

    So, this has been a project for me in that I purchased this lathe not functioning and am getting it back up and running. I would consider myself a "mill" guy and am only a few years into machining. So fixing a machine, learning cnc lathe, learning a new control all at the same time. I know I am crazy. Short backstory on the machine. Its a 94 Okuma Cadet LNC8 with a 5020L control. Was working in a shop I worked in and the building was frequently exposed to power surges. One day this thing powered up after a storm the night before and had SVP start error. After a lot of research and trying a few suspect boards found the servo drive was smoked. I just purchased a reman unit and installed and bam, machine back up. Now after learning the control a bit and figuring out how to load posts, I created a simple test program, set my work offset, and launched it. Everything started fine, rapid over to the work piece and faced the part. As soon as it rapid in X+, I heard a breaker type click and the control shut off. It didn't trip the breaker on the shops control panel and I Still have power at the machine. I have to cycle the power on the side of the machine before the control will turn back on and reboot. Tried this a few more times and in the same section of the program it does the same thing. I am sure its an overcurrent issue caused by binding of the X axis or a damaged X servo. I know it could be a bunch of different things. This forum never ceases to amaze me in the amount of experience and knowledge that you guys have and are willing to share. I can pretty much handle anything that needs to be done once I know what needs to be done. So having said all of that, Has anyone run into this before and have any insight on what I should check next before I give a big pound of flesh to Gosiger to come look at this thing? Thank you very much in advance for all the help.

  2. #2
    Join Date
    Mar 2009

    Re: LNC8 (94) control shutting off mid program

    Congratulations. Make a list of possible causes and check all of them one-by-one.
    1. Could be because of overcurrent as you say. Try:
    - to create overcurrent situation in different ways. For instance, starting the spindle with maximum rpm and moving Z and X axis (rapid) positioning at the same time
    - the best is to make peak current measurements.
    - to make situation of overcurrent a bit easier - reduce feed rate, reduce spindle rpm.
    2. What I would start from. Did you moved the machine to another workshop?
    If yes, then:
    - check the level. double check. Triple check. I had in practice even saddle broken apart because of ( X ) guideways were twisted.
    - check the load percentage of each axis in full stroke length. The load shouldn't exceed 11% without load in any conditions and should be continuous.
    - wiring number one. If the mains cable cross-section is enough for your machine?
    - wiring number two. If there is main transformer ( very big one ) ? Check and double check wiring of the transformer. I have seen in my practice reverse connected. It gives desired voltage and some people think it is correct. No. Input does not serve as output.
    3. Check wiring of Controls power supply. Locate the exact place where the power is disconnected - this helps to understand the root cause.

    If you suspect that X drive causes the current surge, do the experiment: move Z, run spindle, don't touch X. And opposite: Leave spindle and Z in peace, move X only.

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