Fanuc AC Servo Motor A06B-0235-B300 A06B0235B300 AO6B-O235-B3OO

FANUC A06B-0235-B300 | Alpha iS 8/4000 AC Servo Motor — 8 Nm / 4000 rpm / Taper Shaft / 24V Spring Brake / A1000 Absolute

Part Number: A06B-0235-B300

Manufacturer: FANUC Corporation (Japan)

Product Type: AC Brushless Servo Motor — Alpha iS Series

Three Specifications That Define This Motor

8 Nm stall torque at 4,000 rpm. At 2.5 kW, the αiS 8/4000 sits in the mid-range of FANUC's Alpha iS family. Eight Newton-metres means that on a 10mm pitch ball screw at 90% efficiency, the motor sustains approximately 4.5 kN of axial force at near-zero speed — the load condition during deep drilling, facing under heavy chip load, or a Z-axis holding a spindle head assembly against gravity without drift. At 4,000 rpm, the same screw moves at 40 m/min in direct coupling — fast enough for productive rapid traverse without a speed-reduction stage.

24V spring-applied brake. The brake is on by default. The coil must be continuously energised with 24V DC to keep the shaft free. Any event that removes 24V — E-stop, power loss, planned servo-off — immediately releases the coil and the spring closes the brake unconditionally. No software, no CNC, no amplifier needed. This is why vertical axes require spring-applied brakes: the spindle head holds position through every stop, every power cycle, every emergency condition.

Brake sequencing matters for disc life: establish servo lock first, then release the brake. When stopping: decelerate under servo control, engage the brake, then remove servo enable. Applying the brake to a moving shaft accelerates wear.

Taper shaft with key. The taper geometry self-centres the coupling hub as it is drawn onto the shaft with a draw bolt. No manual adjustment, no alignment tools — the hub seats to the same geometric position every time, at first installation or after a motor replacement. The key transmits torque through the key's shear cross-section, a mechanically positive path that does not degrade with service hours or loosen under vibration.

Key Specifications

A06B-0235 Series — B300 Variant Context

All variants share the same 8 Nm stall torque, taper shaft, and IP65 rating. The B300 is for machines with 24V brake supply circuits. The B605 is for machines using 90V brake circuits — confirm the machine's brake supply voltage before ordering.

A1000 Absolute Encoder — No Homing After Power Loss

The A1000 retains multi-turn shaft position through power-off events via a backup battery in the servo amplifier. After any stop, the CNC reads exact position immediately — the brake held the axis, the encoder remembered where it stopped. No homing movement required. On vertical axes where homing requires clearing fixtures from the work area before the movement is safe to execute, this is a significant operational advantage.

Replace the battery at the first low-battery alarm from the amplifier. A depleted battery resets the absolute counter and requires a managed homing cycle before production resumes.

FAQ

Q1: What is the difference between A06B-0235-B300 and A06B-0235-B000?

The only difference is the brake. B000 has no brake — axis position at rest is maintained by servo lock, which requires the amplifier to remain powered. B300 has a spring-applied 24V brake that holds the shaft mechanically whenever the coil is de-energised, regardless of servo state. Use B000 on horizontal axes; use B300 on vertical axes and gravity-loaded mechanisms.

Q2: Does the 24V brake engage automatically during E-stop or power loss?

Yes — unconditionally. The spring holds the brake closed by default. The coil must be continuously energised with 24V DC to keep the shaft free. Any loss of 24V immediately releases the coil and closes the brake. No software or active system is needed. The axis holds at whatever position it occupied when power was removed.

Q3: What amplifier is required for the A06B-0235-B300?

FANUC αi series servo amplifiers (αiSV). The αiSV-20 or αiSV-40 is typical for the αiS 8/4000 power level depending on configuration. Compatible CNC: Series 0i-D/F, 15i, 16i, 18i, 21i, 30i/31i/32i. The motor is not compatible with older α or αC series amplifiers or with FANUC β series drives.

Q4: Does the A1000 absolute encoder eliminate homing after power loss?

Yes. The A1000 retains multi-turn position via the backup battery in the servo amplifier. At restart, the CNC reads current position immediately — no homing movement needed. This is the key operational advantage on vertical axes where homing requires supervised sequencing before the work area is safe to enter.

Q5: What is the difference between B300 (24V) and B605 (90V) brake variants?

Mechanically and electrically identical except for brake coil voltage. B300 operates on 24V DC brake supply; B605 on 90V DC. Most modern FANUC CNC machine tools use 24V brake circuits, making B300 the more common variant. Confirm the machine panel's brake supply voltage before ordering.