1pcs USED GE FANUC A20B-2901-0960 Board Tested A2OB-29O1-O96O A20B29010960

FANUC A20B-2901-0960 | PMC-RB3 / RC3 Module with I/O Link — Used / FANUC Series 16 / 18

PMC and I/O Link — What This Module Controls

The A20B-2901-0960 is the PMC-RB3/RC3 module with I/O Link for FANUC Series 16 and 18 controllers. It handles two functions simultaneously: running the PMC ladder program that sequences the machine tool's automated operations, and managing the I/O Link communication bus that carries all the digital signals between the CNC and distributed I/O devices throughout the machine.

In FANUC's CNC hierarchy, the PMC (Programmable Machine Controller) is the integrated PLC running inside the CNC hardware. It executes the relay logic that controls tool changes, coolant, safety interlocks, operator panel responses, and every other machine automation sequence that runs alongside the CNC's axis motion. The ladder program is stored separately in the FROM module; this board provides the execution engine and the I/O Link bus master that connects the CNC to the machine's I/O.

The I/O Link side is what makes this module different from a simpler PMC board without I/O Link. Every operator panel signal, every field I/O point connected via an I/O Link expansion unit, travels through this bus. When the A20B-2901-0960's I/O Link interface fails, all connected I/O is lost simultaneously — the machine cannot respond to operator inputs, and all panel indicator outputs go dark. That total I/O loss pattern, accompanied by an I/O Link alarm on the CNC display, is the fault signature that points specifically to this module rather than to wiring or field device problems.

Key Specifications

RB3 vs RC3 — PMC Version Compatibility

The PMC-RB3 and PMC-RC3 are different ladder execution versions within the FANUC PMC-RB/RC family. The RB3/RC3 designation on this module defines the ladder language specification — instruction set, maximum step count, execution speed, and I/O addressing — that the PMC program written for this machine depends on. A replacement module must match the installed version; a module with a different PMC version may not execute the existing ladder program correctly even if physically identical.

Before ordering, confirm the installed module's label shows A20B-2901-0960 and verify the machine documentation identifies whether it uses PMC-RB3 or PMC-RC3 at this position..

FAQ

Q1: What are the main symptoms of a failed A20B-2901-0960?

Three recognisable patterns: (1) Complete operator panel loss — no buttons respond, no panel indicators illuminate — accompanied by an I/O Link alarm on the CNC. This is total I/O Link failure and points directly to this module. (2) Erratic I/O behaviour across multiple channels simultaneously rather than a single channel, suggesting the bus master is degraded. (3) PMC ladder alarms that indicate execution errors when individual I/O signals, cables, and field devices are confirmed good.

Q2: Does replacing this module require reloading the PMC ladder?

No. The PMC ladder is stored in the FROM module on the main control board, not in the A20B-2901-0960. After fitting the replacement and powering on, the CNC loads the ladder from FROM as normal. Verify I/O Link communication is restored on the PMC diagnostic screen before returning the machine to production.

Q3: How is a PMC module fault distinguished from field wiring or field device faults?

PMC module failures affect many I/O points simultaneously — all panel functions at once, or the entire I/O Link branch at once. Individual wiring faults affect one or two I/O addresses at a time. If multiple unrelated I/O functions fail simultaneously while the CNC's main axis and programme execution functions remain normal, and individual cables and field devices test good, the PMC module is the fault candidate.

Q4: Can the A20B-2901-0960 be used in both Series 16 and Series 18 systems?

Yes — the module is identified for FANUC Series 16 and 18 Model B/C platforms. The PMC-RB3/RC3 designation and I/O Link interface are common to both CNC families in these model generations. Confirm the exact machine's documentation specifies this part number at the relevant board position before ordering.

Q5: What should be verified when accepting a used A20B-2901-0960?

Confirm the full part number A20B-2901-0960 from the module's label. Request confirmation of the PMC version — RB3 or RC3 — to ensure it matches the machine's ladder program specification. For a used unit, ask whether it was tested on a live Series 16 or 18 system with I/O Link communication verified, not just powered on. Inspect the board's connector contacts for corrosion or mechanical damage before fitting.