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Servo Drive Card – OKUMA VAC III D-11
The VAC III D-11 is a servo drive card (“Velocity Amplifier Card”) manufactured by OKUMA, a component of the axis drive system for CNC machine tools equipped with an OSP (Open System Platform) controller. The card belongs to the third generation of the VAC (Velocity Amplifier Card) series; the D-11 designation identifies the specific power and regulation topology variant. It interfaces the CNC controller with the servo motor power stage, processing the analogue velocity reference and the feedback signal from the resolver or encoder.
The VAC III D-11 is the electronic controller that closes the velocity loop on the axis servo motor: it receives the position/velocity reference from the CNC unit and generates the command signal for the power stage, ensuring precise axis positioning during machining. A failure of this component results in the immediate loss of the affected axis, causing machine downtime and complete inability to resume production until the component is repaired or replaced.
OKUMA is a Japanese machine tool manufacturer founded in 1898 in Oguchi (Aichi, Japan). It is one of the few manufacturers worldwide to produce both machine tools and its own CNC control system (OSP – Open System Platform), ensuring full integration between mechanics and control electronics. Products from the VAC III series are legacy / discontinued: available exclusively as used, surplus, or through specialist repair services.
Main Technical Specifications
| Type | Axis servo drive card / velocity amplifier card (Velocity Amplifier Card) |
| Part number | VAC III D-11 (VACIIID11) |
| Brand | OKUMA |
| Known application | OKUMA CNC machine tools with OSP control (machining centres, lathes, CNC milling machines) |
| Function | Axis servo motor speed and current regulation; velocity loop closure |
| Reference input | Analogue velocity reference ±10 V (typical) |
| Feedback | Resolver / encoder from axis servo motor |
| Logic supply voltages | ±15 V and +5 V DC (typical) |
| Interfaces | On-board connectors for integration in OKUMA CNC rack/cabinet |
| Series generation | VAC III (third generation of the OKUMA Velocity Amplifier Card series) |
| Weight | ~0.5–1.5 kg |
| Dimensions | ~200–350 mm |
| Production status | Legacy / discontinued — used/surplus/repair only |