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| Place of Origin | JAPAN |
| Brand Name | FANUC |
| Certification | CE ROHS |
| Model Number | A06B-0128-B077 |
Part Number: A06B-0128-B077
Series: ALPHA AC Servo Motor
Model: A6 / 3000
Status: Discontinued by Manufacturer — Refurbished & Surplus Stock Available
Condition: Refurbished / Surplus
The Fanuc A06B-0128-B077 is a compact, high-speed ALPHA series AC servo motor — model A6/3000 — from Fanuc's established red-cap motor generation that served the CNC machine tool industry through decades of productive daily use.
At 1.4 kW rated output with 6 Nm stall torque, running to 3,000 RPM on a 114V three-phase supply at 200Hz and drawing 7.5A continuous, this is a purposefully light-framed motor built for the auxiliary axes and secondary positioning drives of small to medium CNC machine tools.
Two physical characteristics define this variant within the A6/3000 family: the taper shaft and the IP67 sealing.
The taper shaft creates a self-centering interference fit with the driven component — a design choice made for precision, repeatability, and reliable torque transmission under the load and cycle profile of the axes this motor was specified on.
The IP67 factory sealing extends service life in the coolant-heavy environments where machine tool servo motors operate, protecting the bearing cavities and winding from the mist and fluid exposure that shortens the life of lower-rated housings.
Fanuc has discontinued this model. The A6/3000 ALPHA motors are well-represented in the refurbishment and surplus market, and the machines built around them continue running in shops and facilities that have no immediate reason to retire equipment that is still producing parts reliably.
| Parameter | Value |
|---|---|
| Rated Output | 1.4 kW (Continuous) |
| Stall Torque | 6 Nm |
| Stall Current | 10 A |
| Rated Current | 7.5 A |
| Motor Voltage | 114 V |
| Rated Frequency | 200 Hz |
| Phase | 3-Phase, Y-Connected |
| Maximum Speed | 3,000 RPM |
| Encoder | I64 Incremental Pulse Coder (64,000 ppr) |
| Shaft Type | Tapered Shaft (with keyway) |
| Brake | None |
| Ingress Protection | IP67 |
| Insulation Class | F |
| Weight | Approx. 12.2 kg |
| Series | ALPHA — A6/3000 |
| Manufacturer Status | Discontinued |
The A6 designation marks this motor at the lower-torque end of the ALPHA mid-size family — 6 Nm stall torque compared to the 12 Nm of the AC12 motors and the 22 Nm of the AC22 family. The 3,000 RPM ceiling places it at the higher-speed end within its torque class.
That combination defines an application niche: fast, light-load positioning drives where cycle time on moderate mechanical loads matters more than sustained force output.
On the machine tools this motor served, the A6/3000 typically handled auxiliary axes — fourth-axis rotary tables on small machining centres, tailstock positioning on compact lathes, tool magazine indexing drives, and secondary positioning functions where the servo axis moves a relatively light mechanism quickly and accurately on a high-cycle basis.
The 3,000 RPM rating, paired with appropriate ballscrew or gearing, delivers the traverse speed these applications need without requiring a larger, heavier motor frame.
The 200Hz electrical frequency reflects this motor's high-speed design.
The ALPHA servo amplifier generates this frequency from a standard 200–230VAC mains supply, producing the 114V motor operating voltage through its internal DC bus and inverter stage. This is transparent to the machine installation — the relevant connection at the drive cabinet is the standard AC supply, not the 200Hz motor frequency.
The taper shaft is the defining mechanical feature of the A06B-0128-B077, and it separates this variant from the straight-shaft versions within the same A6/3000 family.
The precision-ground conical profile of the shaft engages with a matching taper bore in the coupling hub, pulley, or driven component, producing a self-centering interference fit that positions the driven element concentrically with the shaft axis without relying on keyways or clamping force alone.
The fit is completed by a keyway machined into the taper — the key provides positive rotational engagement that prevents the hub from spinning on the taper under shock loads or direction reversals, while the taper geometry ensures the hub seats concentrically every time it is installed.
This combination is typical on precision axes where shaft runout would affect positioning accuracy or surface finish quality, and on drives where the torque profile includes frequent direction changes that plain shaft couplings might not sustain consistently over long service intervals.
The practical consequence at replacement time is that the driven component — whatever is mounted on the taper — must be removed with a proper taper-breaking puller rather than driven off with impact tools. Scoring the taper surface during removal degrades the interference fit geometry on reinstallation, which produces shaft runout that manifests as vibration or axis positioning error during operation.
This is a repair outcome that proper tooling and procedure would have prevented, and it is one of the most common findings on A6/3000 motors returned for service after field maintenance.
The I64 is Fanuc's 64,000 pulse-per-revolution incremental encoder integrated into the rear of the motor housing. It provides the position and velocity feedback signals the ALPHA servo amplifier uses to close the control loops for accurate axis positioning and feedrate regulation.
At 3,000 RPM, the encoder generates 3.2 million pulses per second — the feedback density that supports smooth velocity control and precise position endpoint accuracy across the motor's full speed range.
Incremental operation means absolute axis position is re-established through a homing sequence at each machine startup.
The CNC drives the axis to its reference position, reads the encoder's marker pulse, and the position counter is set from that reference for the rest of the operating shift. For the auxiliary and secondary axes this motor typically serves, homing is a brief and routine part of the startup sequence.
On motors with long service histories, the encoder connector and its cable exit are statistically the most vulnerable components.
Connection quality degrades slowly — from humidity, from thermal cycling in the cabinet environment, or from physical contact during previous maintenance — and the resulting intermittent encoder output can take time to identify when the fault does not produce a consistent alarm pattern.
The IP67 rating on the A06B-0128-B077 is factory standard — not an aftermarket addition. The motor housing, shaft seal, cable entries, and encoder body are all built and certified as an IP67 assembly, rated for temporary immersion up to one metre for 30 minutes.
In a machine tool environment, IP67 means the motor is reliably protected against coolant spray, mist accumulation, and direct fluid contact during cutting operations, workpiece loading, and routine machine cleaning.
At the A6/3000 power class, the motor is typically installed in positions closer to the cutting zone than the larger axis motors — rotary tables, tool changers, and similar compact mechanisms often sit in areas with heavier coolant exposure relative to their size.
The IP67 rating on a motor this size is therefore not conservative overspecification — it is an appropriate match to the environmental reality of where the A6/3000 actually works.
The A06B-0128-B077 is compatible with Fanuc ALPHA series SVM servo amplifier modules. From the GE Fanuc amplifier pairing documentation, the A06B-0128 motor series (which includes the B077) is paired with the SVM1-80 and SVU1-80 amplifier classes.
It integrates with the Fanuc CNC control platforms that were standard during this motor's production period — Series 0, 0i, 15, 16, 18, and 21. The servo amplifier must be parameterised with the motor type code for the A6/3000 before axis operation.
Q1: What is the tapered shaft on this motor, and why does it matter for installation and replacement?
The taper shaft is a precision-ground conical shaft profile that creates a self-centering interference fit with the driven component. It positions the coupling hub or pulley concentrically without relying on shaft clamping alone, and the integrated keyway provides positive rotational engagement.
At replacement time, the driven component must be removed using a proper taper puller — not impact tools — to avoid scoring the taper surface. A scored taper produces shaft runout that causes vibration and positioning error in service. Verify that the replacement motor carries the same taper shaft specification before ordering.
Q2: What servo amplifier should be paired with the A06B-0128-B077?
The A6/3000 ALPHA series requires an ALPHA series SVM or SVU servo amplifier module from the SVM1-80 or SVU1-80 class, paired with Fanuc CNC controls including Series 0, 0i, 15, 16, 18, and 21. The servo drive must be parameterised with the motor type code for the A6/3000 before the axis is run under load.
An incorrect motor type parameter affects velocity loop tuning, current limits, and speed scaling — all of which must be correct before the first production cycle.
Q3: The motor is discontinued — can it be substituted with a current Fanuc motor?
A cross-generation substitution is technically possible but requires more than swapping the motor. Mounting dimensions, shaft geometry, connector pinouts, and encoder interface differ between the ALPHA and current-generation motor families.
The servo amplifier typically needs to be replaced or reconfigured alongside the motor. For a single failed motor on an otherwise functional machine, sourcing a refurbished A06B-0128-B077 and returning the axis to original specification is usually the faster, lower-risk path back to production.
Q4: What is the difference between the B077 and B177 variants in the A6/3000 family?
Both the B077 and B177 share the same 1.4 kW output, 6 Nm stall torque, 114V / 200Hz / 7.5A electrical specification, taper shaft, I64 encoder, and IP67 sealing. The single difference is the brake: the B077 has no integrated brake, while the B177 carries a spring-applied electromagnetic holding brake.
The brake variant is used where mechanical position retention is required when the servo is inactive — typically vertical axes or gravity-loaded mechanisms. For horizontal axes where the servo drive provides position holding through active torque, the B077 brakes-free variant is the correct specification.
Q5: What checks are most important when evaluating a used A06B-0128-B077?
Start with the taper shaft surface — inspect carefully for fretting marks, scoring, or impact damage from previous improper removal. Taper surface damage compromises the interference fit and cannot be repaired in the field without specialist shaft regrinding.
Then inspect the I64 encoder connector for corroded or bent pins and the cable exit for chafing or damage. Measure three-phase winding resistance for balance and verify insulation resistance to earth. Rotate the shaft by hand to assess bearing condition.
A bench run-up to 3,000 RPM with encoder output verification on a Fanuc ALPHA drive is the correct final check before the motor returns to a production axis.
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