How to Identify a Fanuc Servo Motor — the A06B Order Number Decoded

Ordering the wrong servo motor is one of the most expensive mistakes in CNC maintenance — a motor that bolts on but has the wrong shaft, no brake, or the wrong Pulsecoder leaves the machine just as dead. The good news: a Fanuc servo motor's full specification is encoded in its A06B order number, and once you can read it, you can identify any motor from its nameplate in under a minute. Here is the format, decoded from Fanuc's own ordering specification.

The format

A06B – □□□□ – B △ ○ ▽ # ◎◎◎◎

Reading left to right: the model code, then — after the B — three single digits for shaft, brake/fan, and Pulsecoder, and finally a four-digit suffix after the #.

□□□□ — The motor model

The four digits after A06B identify the motor family and size (for example 0075, 0212, 0227…) — these map to specific models like βiS 4/4000 or αiF 8/3000 in Fanuc's ordering tables. This is the part that must match exactly; the digits that follow describe the build options on that model. Note Fanuc's own caution: not every combination exists — which is why an ‘equivalent’ number that almost matches often doesn't exist as a real product.

△ — First digit after B: shaft & brake

Rule of thumb: 0–2 = no brake, 3–5 = built-in 24 V brake. This digit is the classic Z-axis trap — vertical axes need the brake versions (3–5), and a broken motor replaced with the no-brake variant will drop the head the moment servos release. Fanuc also warns: don't select the key-groove shaft (2) where large torque or abrupt acceleration is required.

○ — Second digit: brake torque & cooling fan

Note the linkage rule from the manual: if this digit is 2 or 3 (high-torque brake), the shaft digit must be 3–5 — a high-torque brake only exists on brake-equipped shafts.

▽ — Third digit: the Pulsecoder

This is the digit that bites during repairs: a replacement motor with the wrong Pulsecoder type will not run correctly with your amplifier settings — and absolute vs incremental changes how the machine references (see our zero return guide). If only the encoder has failed, replacing the Pulsecoder alone is usually far cheaper than the motor: pulse coder replacement guide.

#◎◎◎◎ — The suffix

On machines where the motor lives under coolant spray, the IP67 suffix matters — fitting a standard motor where an IP67 unit was specified invites the insulation failures behind overcurrent alarms.

Worked example

Take A06B-0075-B403#0000:

• 0075 — the motor model (a βiS-family motor in the ordering tables)
• 4 — straight shaft with a 24VDC brake (a Z-axis build)
• 0 — standard: no fan, standard brake torque
• 3 — Pulsecoder per that model generation's encoder table
• #0000 — standard sealing

Change any one of those digits and it is a different product — the same motor family with a different shaft, brake, cooling or encoder. Two motors are interchangeable only when you understand exactly which digit differs and what it changes. And because not every combination exists, always confirm a substitute number against Fanuc's tables (or ask us) — never construct one by analogy.

Identifying a motor with a damaged nameplate

1. Photograph what remains of the nameplate — even partial A06B digits narrow it fast.
2. Look at the physical build: brake wires in the connector = brake version; fan housing on the tail = fan version; taper vs straight shaft is visible at the coupling.
3. Read the Pulsecoder label under the encoder cover — the encoder model confirms the third digit.
4. Check the amplifier it ran on — the drive's motor-ID parameter (2020) tells you the motor model the machine expects.
5. Still unsure? WhatsApp us photos of the motor, shaft end and connectors — identifying Fanuc motors from photographs is daily work for us.

Related guides

• Browse Fanuc αi servo motors in stock (αiS / αiF, 200 V & 400 V)
• Fanuc encoders & Pulsecoders — stock and repair
• How to read Fanuc part numbers from a PCB (A16B/A20B/A02B)
• Identifying and replacing a faulty Fanuc encoder
• Top 5 signs your servo motor needs replacement