control board 6FC5357-0BB22-0AE0 6FC5 357-0BB22-0AE0 6FC5357-OBB22-OAEO

Siemens 6FC5357-0BB22-0AE0 | SINUMERIK 840D / DE Numerical Control Unit NCU 572.3 — AMD K6-2 / Without System Software

Part Number: 6FC5357-0BB22-0AE0

Manufacturer: Siemens AG (Germany)

Product Type: NCU — Numerical Control Unit 572.3

CNC Platform: SINUMERIK 840D / 840DE

NCU 572 — Mid-Range Processor Generation

The 6FC5357-0BB22-0AE0 is the NCU 572.3 for Siemens SINUMERIK 840D and 840DE CNC systems. The NCU is the core processing module — it runs all CNC interpolation, axis control, PLC logic, and PROFIBUS communication simultaneously from a single board. It mounts in the NCU box alongside the fan/battery slide-in module and the power supply, which form the complete control unit assembly.

The 572.3 designation identifies this as the third revision of the NCU 572 family. The AMD K6-2 processor at 233 MHz places this unit in the SINUMERIK 840D's mid-1990s to early-2000s hardware generation — the generation before the Pentium III-based NCU 573 series. The 572.3's NC memory (0.5 MB) is smaller than the 573.3's 2.5 MB, which affects the size of part programs the CNC can hold in active memory.

Within the NCU 572 sub-series, successive variants (0AE0, 0AE1, 0AE2) reflect incremental hardware revisions. The 0AE0 is the base revision. The system software loaded must be appropriate for the NCU 572 hardware generation — software versions designed for NCU 573 are not compatible with the NCU 572 processor and memory architecture.

NCU 572 vs NCU 573 — Generation Comparison

The NCU 572.3 and 573.3 are not interchangeable — each requires the matching system software version for its processor generation.

Key Specifications

FAQ

Q1: The 840D CNC fails to boot after the NCU was replaced. What should be checked first?

Confirm the NCU is fully seated in the NCU box and the system software PC card is installed and correctly seated. Without the software card, the NCU cannot start. Also verify the 24V power supply to the NCU box is within specification. Missing or low 24V is a common cause of boot failure after hardware replacement.

Q2: Can the NCU 572.3 (0AE0) be replaced by an NCU 573.3 if the 572.3 is unavailable?

No — the two are different processor generations requiring different system software. The NCU 573.3 uses Pentium III and requires software built for that hardware. Fitting a 573.3 in a system with 572-compatible software produces an incompatible combination. Source a 572.3 variant or plan a complete system software migration.

Q3: The system software PC card must be loaded separately. What software version is required?

The software version must be compatible with the NCU 572 hardware generation. Software designed for NCU 573 is not applicable here. Confirm the original machine's software version from the existing NCU label or the machine tool builder's documentation before sourcing the replacement software card.

Q4: No machine data backup exists. What is needed before the machine can run after NCU replacement?

A complete recommission is required: enter NC machine data from the MTB documentation, load and compile the PLC program from source, and commission SIMODRIVE 611D drives with correct motor and encoder data. Allow several days without a backup file.

Q5: After replacing the NCU, PROFIBUS communication to I/O modules is not working. What should be checked?

The PROFIBUS node address and configuration parameters are stored on the NCU — a replacement NCU boots with default settings. Re-enter the correct PROFIBUS DP address and verify all PROFIBUS communication parameters match the original configuration.