Main Circuit Board A16B-3200-0020 A16B-32OO-OO2O A16B32000020

A16B-3200-0020 | FANUC Series 21-TB Main CPU Board — 4-Axis / 3 Slots / SERVO / PMC / MEM & SP / Front-Mount Connectors

Series 21-TB — Compact CNC for Turning

The FANUC Series 21 occupied a specific market position in FANUC's CNC lineup: more capable than the economy Series 0, but more compact and lower-cost than the full Series 16/18. The "21" designation placed it between these generations, offering a balanced combination of features for small to medium turning centres (21-TB) and machining centres (21-MB).

The 21-TB (Turning Centre) configuration tailored the system for lathe applications: tool nose radius compensation, constant surface speed, threading, and turning-specific canned cycles as standard.

The A16B-3200-0020 is the main CPU board for this 21-TB control — the physical core that all other boards and modules connect to and depend on.

Key Specifications

4-Axis Capability

The A16B-3200-0020 supports up to 4 controlled axes — sufficient for most turning centre configurations:

• Standard 2-axis lathe (X and Z): Two of the four capacity is used
• 3-axis lathe with Y-axis or sub-spindle: Three axes used
• 4-axis twin-turret lathe (X1, Z1, X2, Z2): Full four-axis capacity used

For a machine requiring more axes, the Series 16 or 18 would be the appropriate platform. The 21-TB's four-axis capacity is well-matched to the turning machines it typically equips.

Application Scenarios

21-TB CNC main board failure: A CNC turning centre with FANUC 21-TB control loses all response after power-on. Supply voltages confirm correct; the A16B-3200-0020 main board is identified as the fault. Replacement — with the servo, PMC, and MEM & SP modules re-installed — and a parameter restore from backup returns the machine to production.

CNC control system refurbishment: An older 21-TB turning centre is refurbished for continued service. The A16B-3200-0020 main board is replaced as part of an overall control unit renewal.

FAQ

Q1: What modules must be transferred to the replacement A16B-3200-0020?

All three slot modules — the SERVO card, the PMC module, and the MEM & SP module — must be removed from the old board and installed in the same slots on the replacement. These modules carry the CNC's software and configured data. Additionally, FROM/SRAM modules (programme and parameter storage) on the main board must be transferred intact.

Q2: Is the A16B-3200-0020 compatible with the Series 21-MB (machining centre) variant?

The A16B-3200-0020 is confirmed for the 21-TB turning centre. The 21-MB (machining centre) may use a different main board variant with different slot configurations or software support. CNC Electronics notes this board as "21B control system series CPU PCB" which covers the 21-series platform. Verify from the specific machine's spare parts documentation before ordering.

Q3: What happens to CNC programmes when the A16B-3200-0020 is replaced?

If the MEM & SP module and FROM/SRAM modules are transferred intact from the original board, all programmes, parameters, and PMC data are preserved. If these modules are not available (e.g., damaged), a complete data restore from backup is required. This is why performing a backup before any main board maintenance is essential practice

Q4: Is firmware update required after fitting a replacement A16B-3200-0020?

CNC system firmware is stored in the FROM (Flash ROM) modules — separate from the main board. If the FROM modules from the original system are transferred to the replacement board, the firmware is preserved and no reflashing is needed. If new FROM modules must be used, the correct FANUC firmware version for the 21-TB must be loaded.