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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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  2. #2
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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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