Fanuc AC Servo Motor A06B-0243-B400 A06B0243B400 AO6B-O243-B4OO

FANUC A06B-0243-B400 | Alpha iF 12/4000 AC Servo Motor — 2.5 kW / 12 Nm / 24VDC Brake / Straight Shaft

AiF 12/4000 — Where 12 Nm and 3000 rpm Intersect

The A06B-0243-B400 is FANUC's AiF 12/4000 servo motor — 12 Nm stall torque at up to 3,000 rpm, 2.5 kW output. The AiF designation identifies the Alpha iF (flange-mount) series — the motor family matched to FANUC's Alpha i servo amplifier architecture and used across the 16i/18i/21i and 0i CNC platform generation.

At 12 Nm stall torque, this motor handles the type of servo axis that needs real sustained torque capability: CNC lathe turret drives, vertical machining centre Z-axis feeds, rotary table inputs, and press and stamping feed axes where moderate speed and genuine torque authority are both required. The 3,000 rpm maximum speed and 2.5 kW output place it in the mid-range of the AiF family.

The 24V DC brake is a key specification on this variant. Confirm from the installed motor's label whether the brake is spring-applied (engages by default at power-off — standard for vertical axes) or energise-to-release type. For vertical axes and gravity-loaded mechanisms, spring-applied is the correct brake type. The B400 suffix confirms the straight-shaft, brake-equipped, A1000 encoder configuration of this variant within the A06B-0243 series.

A1000 / AiA1000 Encoder — Incremental Feedback

The A1000/AiA1000 pulsecoder is an incremental encoder type. At each machine power-up, a reference-return cycle is required to establish the axis position reference before production can start. The CNC cannot use the axis at a known position until this homing cycle completes.

For machines requiring absolute position on power-up without a homing cycle, the variant with an absolute pulsecoder in the A06B-0243 series is the correct specification. Confirm the installed motor's encoder type from its nameplate before ordering

Key Specifications

Straight Shaft — Coupling Compatibility

The straight shaft on the B400 mates with friction-clamp coupling hubs. Verify the existing coupling hub's bore diameter matches the motor shaft diameter before fitting. The straight shaft does not require a keyed hub unless the coupling is designed for a keyed interface. For high-torque applications with frequent reversals where coupling slip is a concern, a coupling that uses both a bore clamp and a setscrew provides better long-term retention than a plain friction bore alone.

FAQ

Q1: What servo amplifiers are compatible with the A06B-0243-B400?

The AiF 12/4000 pairs with FANUC Alpha i SVM servo amplifier modules from the A06B-6114 series. The specific SVM variant depends on the drive system's axis count configuration. Confirm the amplifier's rated current covers the motor's 7A rated current. Verify the amplifier supports the A1000/AiA1000 incremental encoder interface.

Q2: The machine requires a homing cycle at every power-up. Is this because of the A1000 encoder?

Yes. The A1000 is incremental — it establishes position by counting pulses from a reference point at each power-up. A homing cycle is required before the axis is usable at a known position. If the application requires absolute position without homing, specify the A06B-0243 variant with an absolute pulsecoder (different B suffix).

Q3: The 24V brake is not releasing when the drive is enabled. Confirmed 24V at the motor connector. What should be checked?

With 24V confirmed at the connector, measure the brake coil resistance (24V disconnected). A healthy coil on a motor of this size typically reads in the 20–60 Ω range. Open circuit confirms a failed coil. If resistance is within range, check for mechanical binding — contamination between the brake disc and friction surfaces can prevent release even with correct coil current.

Q4: After replacing with A06B-0243-B400, the axis following error is larger than before. What should be investigated?

Verify the servo amplifier's motor type parameter matches the AiF 12/4000 specification — a parameter mismatch produces a consistent following error. Also check that the encoder cable is fully seated at the amplifier's feedback connector and that the cable shielding is correctly grounded. Mechanical coupling misalignment after motor replacement adds friction that increases following error and should be checked before adjusting servo gains.

Q5: Where is the A06B-0243-B400 sourced?

Through the FANUC Alpha iF series motor aftermarket — new surplus, tested refurbished, and motor rebuild services. Confirm the B400 suffix (straight shaft, 24V brake, A1000/AiA1000 encoder) from the installed motor's nameplate before ordering. Brake function and encoder operation should both be verified in acceptance testing for any exchange unit.