Our Team Expertly Repairs Okuma VAC Spindle Drives

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

Okuma’s original VAC drive, the VAC-I spindle, is the first iteration in the VAC spindle line. This drive sets the standard for VAC spindle units and employs a lot of the functionality that was continued in the VAC-II and VAC-III units. With offerings ranging from 3.7kW to 37kW, this spindle drive is powerful and versatile. The VAC-I has multiple revisions that distinguish different versions of the control board used. When one of these spindles has a ‘-A’ appended to the end of the model number, new version control is signified.

The new type VAC-I drive improves upon the original unit and also offers a high power model as well as updated software versions. The VAC-I is a sturdy and dependable unit capable of driving up to 37kW of power to run the larger VAC series motors.

When assessing the functionality of a drive like this Okuma VAC-I 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 mega ohm 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-I 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. 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, printed circuit boards 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 first part of the basic static check is to verify that the inputs have not failed. We use multimeters to check the resistance between phases as well as phase to ground resistance. Ideally, phase to phase and phase to ground measurements should all show as infinite (open) resistance.

Ouput Module Testing

Precision Zone repair technicians use digital multimeters with diode testing capabilities and also take resistance measurements to conduct a static test. For these units in particular, our team of technicians uses the diode function of the multimeter as well as huntron devices to check the output modules.

Positive Lead Negative Lead Reading
U Positive Bus Terminal 0.30V-0.35V
V Positive Bus Terminal 0.30V-0.35V
W Positive Bus Terminal 0.30V-0.35V
Negative Bus Terminal U 0.30V-0.35V
Negative Bus Terminal V 0.30V-0.35V
Negative Bus Terminal W 0.30V-0.35V

The capacitor values on the PCBs are verified and any relays, contactors or circuit breakers in the drive are examined to ensure proper functionality. All fuses are checked to make sure none have failed.

Checks Under Power and Alarm Code Verification

Upon successfully passing all visual and static checks, the drive is tested under power. Any reported alarm codes are verified and if no alarms are present or once the drive has been fully repaired, the drive is tested in our Okuma simulator. Switch settings are recorded and the drive is powered up to check for any alarms. Alarms and drive status can be verified on the LEDs directly on the spindle unit.

On the VAC unit, there are a handful of LEDs to display alarm status. A CPUALM LED that indicates an alarm and problem with the operation circuit. A red LOSS LED indicates a problem with the voltage to the drive and control board. The M1, M2, and M3 LEDs are important to monitor as these three LEDs indicate faulty operation and should all be OFF for normal running operation. The cover of the drive gives the alarm code corresponding to the illuminated LED. Depending on which LED (M1, M2 or M3) are on, designates a various alarm. Some descriptions are given in the table below.

Okuma VAC-I AC Spindle Drive Common Alarms and Warnings

Alarm Code Description Quick Checks
OV Power Circuit Overvoltage
  • Check the output signals of the encoder are present and correct (use oscilloscope)
  • Change magnetic encoder sensor or gear
PH Phase Loss
  • Check to make sure main breaker on drive is on
  • Check all three phases of incoming. All should be balanced and within the proper voltage range
  • Check fuses F5, F6, F7
OS Overspeed
  • Resolver may be faulty
  • Loose connection of connectors or feedback cables
  • Control board may need repair if the encoder and cables check out. Make sure there are no breaks in the cables
IOCM Motor Cable Overcurrent
  • Check terminal screws are tightly secured
  • Check motor and motor cables for short circuits. Use megger to obtain winding resistance values
IOCR Regenerative Transistor Short
  • Check the power supply. An instantaneous power failure may have occurred
  • Check the fuse and IGBT on the control board
OL Motor Overloaded
  • Check that all connectors at drive and motor are inserted properly
  • Check the motor cables for short circuits
  • Check resistance of the thermostat relay terminals. The resistance should not be infinite
ACC Microcomputer Access Error
  • Try to reset drive - cycle power
  • Verify switch settings
  • Control board failure

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 VAC 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 VAC-I D8-A image VAC-I D8-A is an
Drives-AC Spindle manufactured by Okuma
Discovered issues: Bad Capacitor(s), Bad Circuit Board Component(s), Bad Gate Section/Board, Leaky Capacitors (Open, Corroded Traces), Bad Magnetic Contactor, Relay
Drive Type: VAC-I AC Spindle Drive
Rated Capacity: 8kW
Design Revision Order: A (Control board is E4809-045-084-D or higher)

Okuma VAC-I D11 image VAC-I D11 is an
Drives-AC Spindle manufactured by Okuma
Discovered issues: Bad Circuit Board Component(s), Bad Magnetic Contactor, Relay, Bad Power Board, Bad Precharge Resistor, Excessive Dirt/Debris
Drive Type: VAC-I AC Spindle Drive
Rated Capacity: 11kW
Design Revision Order: None (Control board is E4809-045-084-A/B/C only)

Okuma VAC-I D22-A image VAC-I D22-A is an
Drives-AC Spindle manufactured by Okuma
Discovered issues: Bad Output Transistors/SCRs
Drive Type: VAC-I AC Spindle Drive
Rated Capacity: 22kW
Design Revision Order: A (Control board is E4809-045-084-D or higher)

Okuma VAC-I D8-B image VAC-I D8-B is an
Drives-AC Spindle manufactured by Okuma
Discovered issues: Bad Circuit Board Component(s)
Drive Type: VAC-I AC Spindle Drive
Rated Capacity: 8kW
Design Revision Order: B (Control board is E4809-045-140)

Okuma VAC-I D37-A image VAC-I D37-A is an
Drives-AC Spindle manufactured by Okuma
Discovered issues: Bad Capacitor(s), Bad Circuit Board Component(s), Leaky Capacitors (Open, Corroded Traces)
Drive Type: VAC-I AC Spindle Drive
Rated Capacity: 37kW
Design Revision Order: A (Control board is E4809-045-084-D or higher)