Motherboard 6FC5357-0BB33-0AE2 6FC5 357-0BB33-0AE2 6FC5357-OBB33-OAE2

Siemens 6FC5357-0BB33-0AE2 | SINUMERIK 840D / DE Numerical Control Unit NCU 573.3 — Without System Software

Part Number: 6FC5357-0BB33-0AE2

Manufacturer: Siemens AG (Germany)

Product Type: NCU — Numerical Control Unit 573.3 

The CNC's Processing Core

The 6FC5357-0BB33-0AE2 is the NCU 573.3 for the Siemens SINUMERIK 840D — the module that executes all CNC and PLC functions in a single board. The NCU is not a peripheral or option board. It is the central processing unit of the SINUMERIK 840D system: NC interpolation, axis control, PLC execution, and PROFIBUS communication all run on this one module.

The integrated S7-300 PLC (315-2 DP, 96 KB) runs the machine's PMC logic — handling the machine tool's I/O, tool change sequences, safety interlocks, and auxiliary functions — alongside the NC's axis control and part program execution. Both NC and PLC functions share the same hardware, making the NCU a highly integrated solution for machine tool control.

The 840D operates with SIMODRIVE 611D drive modules, which interface to the NCU via the drive bus on the NCU box's backplane. The NCU box itself houses the NCU module alongside the fan/battery slide-in module and the power supply — a self-contained architecture that keeps the control electronics compact.

Software Loading Requirement

This unit is supplied without system software. The NC operating system, PLC runtime, and any enabled software options must be loaded from a separate SINUMERIK software card (PC card) before the unit can operate. The system software version loaded must be compatible with the NCU hardware revision. Adjacent NCU 573.3 variants in this series — 0AE1 (Pentium II) and 0AE3 (650 MHz Pentium III) — accept the same software stream but differ in processor speed.

Machine data backup (NC data, PLC program, drive parameters) should be performed on the original NCU before replacement. Without a backup, full recommissioning is required.

Key Specifications

FAQ

Q1: The SINUMERIK 840D shows alarm 120002 (NCU failure) or the system does not boot. Is the NCU 573.3 the cause?

Alarm 120002 or a complete failure to boot indicates a hardware fault on the NCU. Before replacing the NCU, confirm the 24V power supply to the NCU box is within specification and the battery/fan slide-in module is correctly seated. If supplies are confirmed good and the NCU still fails to initialise, the NCU board has failed.

Q2: The replacement 6FC5357-0BB33-0AE2 has no software. What must be loaded before the machine can run?

Load the SINUMERIK 840D system software from the software PC card matching the original software version. Then restore the machine data backup: NC data, PLC program, and SIMODRIVE 611D drive parameters. Without the machine data backup, full recommissioning from documentation is required.

Q3: Can the 0AE2 variant be replaced by 0AE3 (650 MHz) if the 500 MHz version is unavailable?

The 0AE3 NCU 573.3 uses a faster Pentium III (650 MHz) and 64 MB DRAM but is otherwise compatible with the same 840D system software and machine data format. In most 840D applications, 0AE3 can substitute for 0AE2 — but confirm with Siemens service or the machine tool builder if the machine has specific hardware revision requirements.

Q4: The original NCU has failed and no machine data backup exists. How should recommissioning be approached?

Collect the MTB's original commissioning documentation, the SIMODRIVE 611D parameter lists, and the SINUMERIK 840D machine data manual. Load the system software, enter NC machine data from documentation, compile and load the PLC program from source, and commission SIMODRIVE 611D drives using motor data from their nameplates. Allow several days for a full recommission without a backup.

Q5: The drive bus connection between the NCU and SIMODRIVE 611D modules is showing communication errors after the NCU was replaced. What should be checked?

After NCU replacement, verify the SIMODRIVE 611D drive bus cables are fully re-seated in the NCU box backplane connectors. Drive bus communication errors after board replacement are most commonly caused by incompletely seated connectors. If connections are confirmed good, verify that the SIMODRIVE 611D axis parameters (motor type, encoder type) are correctly loaded from the backup.