Okuma VAC-IV Spindle Drive Repair Experts

Here at Precision Zone, one of our specialties is the repair services of Okuma AC spindle units. One series that we often work on is the VAC-IV series of AC spindles.

Okuma VAC-IV spindle units are offered in three sizes - 6kW, 11kW, and 22kW. Each unit is capable of running an array of different sized motors - 6kW can run 3.7kW, 5.5kW, and 6.5kW motors; 11kW can run 11kW or 15kW motors; 22kW can run 18.5kW, 22kW, or 30kW motors. This series of spindle drives also come with 7-segment displays easily visible on the top card. These displays show the drive status during normal operation as well as error status. When the unit enters error status, a corresponding alarm code is shown on these 7-segment displays allowing for quick and convenient troubleshooting.

Monitoring terminals can also be found on the top card of these units and allow a list of essential information to be viewed or gathered using an oscilloscope. These include - 'M1', which shows the motor velocity; 'M2', showing the motors output torque; 'A', 'B', and 'Z', shows the corresponding magnetic encoder phase signal; 'R1', giving the resolver feedback signal; 'S1' and 'S2' show us resolver magnetization signals; 'IS' displays the current on the P side of the DC bus while 'IR' shows the current of the N side; 'IU' and 'IV' show the motor current on the U and V phase, corresponding to their monitoring terminal. There is also a 'GND' terminal which can be used as the ground for each of these checks.

When assessing the functionality of a drive like this Okuma VAC-IV spindle drive, our repair team conducts a four-step evaluation:

    1. Visual Overview
    2. Static Test
    3. Checks Under Power
    4. Alarm Code Verification

This overview is Precision Zone's basic troubleshooting process. Once our repair team starts on the job, we use specialized and customized testing fixtures, Huntron trackers, signal generators, oscilloscopes, milli and megaohm meters, as well as any other necessary tools we have available to assure quality repair work. Most importantly, every repair is fully tested in our custom-built simulators under load with a motor to replicate real-life working environment.

Precision Zone goes as far as using heating chambers and overnight dynamic testing, when applicable, to guarantee performance of the repaired product when it arrives back with the customer.

Repair Process for Okuma VAC-IV Spindle Drives

Visual Overview Check

When conducting a visual check, the technician inspects the drive for any mechanical damage to the drive itself and any printed circuit boards (PCB). The technician then proceeds to verify connections are tight and correct inside the drive and there are no loose screws, wires or debris. Additionally, the unit is checked for any burn marks on the components, PCBs or chassis. During the visual inspection, excessive dirt on cooling components is noted as well as the functionality of the heat sink.

Basic Static Check

Input Module Testing

The input modules on these units cannot be tested by use of a digital multimeter due to extra components found within the input circuitry.

Ouput Module Testing

The output modules are able to be checked with a digital multimeter which has diode checking capabilities. These module ratings differ by drive capacity, so the biggest concern is that the following readings are within 10% of one another. Our technicians are also equipped with huntron devices further verify their integrity.

Positive Lead Negative Lead Reading
U 'P/+' Terminal 0.31V-0.43V
V 'P/+' Terminal 0.31V-0.43V
W 'P/+' Terminal 0.31V-0.43V
'N/-' Terminal R 0.31V-0.43V
'N/-' Terminal S 0.31V-0.43V
'N/-' Terminal T 0.31V-0.43V

Okuma VAC-IV Common Alarms and Warnings

Alarm Code Description Checks
Diff Over
The machine has experienced an overload or a control PCB has occurred
  • Verify cutting conditions are proper
  • PInspect mechanical system for any errors
  • Perform Megaohm test on motor
  • swap drive out with another, if applicable
Motor Wire Overcurrent
Overcurrent has been detected flowing through the unit
  • Check cables for poor insulation
  • Perform megaohm test on motor
  • Use "Output" Module Testing" to verify modules
  • Check for ground faults
Regen Transistor Failure
A short circuit has been detected within the regenerative IGBT module(s)
  • Verify motor load is not excessive
  • View link below for table 4-4(b)
Excessive Speed Deviation
Mismatch detected between commanded speed and physical sped of motor
  • Check if motor is overloaded
  • Perform megohm test to ensure power cable integrity
  • Inspect feedback cable, swap with a known good cable if applicable
  • If winding select contact is used, verify proper state changes

You can find the full list of alarm troubleshooting in the manual, here

This list of checks for certain alarms is primarily a good starting point and if any further troubleshooting or technical support is needed, feel free to contact us via phone or email to get in touch with our experienced tech support team.

For more information on these alarms as well as any other failures, please give us a call at 800-551-4420 or email us today!

Precision Zone Repair Benefits for Okuma Spindle Drives

    1. FREE evaluation by expert technician includes:
    • Visual Inspection
    • Static Check
    • Power Tests
    2. FREE job estimate
    3. 12 month warranty on our parts and labor
    4. Flat Price
    5. Exchange Option
    6. Rush Service

Recently Repaired Products

Okuma VACIV-D22 image VACIV-D22 is an
Drives-AC Spindle manufactured by Okuma
Discovered issues: Bad Control Section/Board, Bad Orientation/Encoder Section/Board
Drive Type: VACIV AC Spindle Drive
Rated Capacity: 22kW

Okuma VACIV-D11 image VACIV-D11 is an
Drives-AC Spindle manufactured by Okuma
Discovered issues: Bad Capacitor(s), Bad Circuit Board Component(s), Bad Gate Section/Board
Drive Type: VACIV AC Spindle Drive
Rated Capacity: 11kW