Selecting the correct Fanuc VCU for a servo (Plus Servo error & Tuning)


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Thread: Selecting the correct Fanuc VCU for a servo (Plus Servo error & Tuning)

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    Default Selecting the correct Fanuc VCU for a servo (Plus Servo error & Tuning)

    First a little background on my situation...
    I have semi-successfully added a rotary 4th axis to my Fanuc 11M based Kuraki KV-700 VMC.
    In the process of doing this, I picked up some very inexpensive used components from a local shop parting out a multi-turret Hitachi lathe.
    The parts (VCU: 6050-H104 & SERVO: A06B-0502-B002) match the Z-Axis on my machine 100%.

    Once I had that 4th servo running I purchased a Nikken CNC-200 Rotary table with servo A06B-0313-B001 (Model O, 2000 PPR - Incremental).

    I proceeded to wire up the table, plumbed air for the brake, and set the parameters for CMR/DMR, etc from the Nikken-supplied spec-sheet.

    When I try to jog the table, I get excess servo error unless I put the rapid-override switch in the "LOW" position. (I have 100%, 50%, 25%, LOW).
    Using the handwheel or moving with G1 at a slower feed-rate the servo functions smoothly and the position is correct on the display

    Checking the diagnostic data reveals that I am getting a ton of servo error which corresponds to the feed-rate of the axis.
    I attempted using the procedure for adjusting the RV1, RV2, RV3 gain potentiometers on the H104 VCU, but the best setting leaves one of the pots at it's minimum gain setting and is still too aggressive, the excess error still causes an alarm.

    I checked all of the in-position error parameters and the in-position-width, etc... They are set per the Nikken spec-sheet and seem to be sensible values.

    My conclusion is that this H104 VCU is too large and I need the smaller 6050-H102 VCU that is appropriately sized and tuned for the model O servo.

    Am I on the right track or am I missing something?

    Thanks in advance for any suggestions/help/etc.

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    Default Re: Selecting the correct Fanuc VCU for a servo (Plus Servo error & Tuning)

    Can you send me the nikken setup sheet? I have the same servo motor but a omc control and I need to change the gear ratio.

    Thanks,
    Micheal

    - - - Updated - - -

    Can you send me the nikken setup sheet? I have the same servo motor but a omc control and I need to change the gear ratio.

    Thanks,
    Micheal



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    Default Re: Selecting the correct Fanuc VCU for a servo (Plus Servo error & Tuning)

    I am revisiting this project. The last I worked on it I purchased the H102 VCU and have everything wired into the machine. With the "standard" jumper settings for the Model 0 servo and H102 VCU as listed in the Fanuc 10/11/12 manual, I have vibration at the servo and the error quickly increases before the machine throws an alarm for "Excess Error".

    This is an old thread, but I'm bringing it back hoping someone has some suggestions to try.

    Michael, I didn't see your response/request before now. If you need anything from my original Nikken CNC-200 documentation, let me know (Send a PM or E-mail to ensure I see it quickly).
    I was incorrect on that servo number above. My table uses the A06B-0513-B001#7000 servo.

    Incidentally, noticing that servo model number mistake in my original post has me onto something. The spec sheet for my Nikken table calls out the 313 (Model 0S) servo... My table has a 513 (Model 0) servo... The spec sheet I have is for Nikken serial number 3086. I have the table with serial number 3083, hence the discrepancy. Parameter number 1874 is the motor model number for the 10M/11M/12M/15M controls (1820 in the 0M control) and it is set as 31 corresponding to the 313 (Model 0S). I will try setting the motor model number parameter (1874) to 51 for my 513 (Model 0) servo... it's worth a shot!



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    Default Re: Selecting the correct Fanuc VCU for a servo (Plus Servo error & Tuning)

    Problem solved... I played around with this a little tonight. I solved the issue by changing the Servo Gain Multiplier (Parameter 1826). Seems to be 100 percent functional, time to make some chips.



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Selecting the correct Fanuc VCU for a servo (Plus Servo error & Tuning)
Selecting the correct Fanuc VCU for a servo (Plus Servo error & Tuning)