Changing SINUMERIK 840C HMI Language from German to English

SINUMERIK 840C HMI Language Change Overview

The SINUMERIK 840C is a CNC controller family from Siemens that paired an NCK (numerical control kernel) with a separate MMC (Man-Machine Communication) panel for operator interface, parameter editing, and program management. The MMC hosted a German-first HMI by default and shipped with multilingual HMI software disks (Sprachpakete) that allowed the operator area to be switched to English, French, Italian, Spanish, or additional languages, depending on what the OEM loaded at commissioning.

Restoring an HMI that was previously English but is now displayed in German is a common field task on legacy 840C installations such as the Index G200, Gildemeister, Boehringer, or Deckel Maho retrofits. The cause is almost always a PLC or NCK backup restore from a machine built for the German market, an MMC cold start that has fallen back to the default disk, or a battery-backed RAM loss on the MMC. The fix is built into the HMI Start-Up area and does not require any external loader, disk, or programming device when the language pack is already installed on the MMC hard disk or flash.

System Identification Prerequisites

Before changing the HMI language, capture the following data so the procedure can be reversed or repeated without losing context:

1. Controller family and type plate: confirm 6FC5...-1AB... or 6FC5...-1AD... MMC part number on the rear of the panel. The 840C and 840CE share the same HMI family but 840CE adds the CE safety PLC layer.
2. Software version: navigate to Diagnose > IBN > SW-Stand (Diagnosis > Start-up > SW version) and record the version string. Common 840C software versions seen in the field include SW 4.06.01, 5.04.x, 5.05.x, 6.01.x, and 6.03.x. The OEM Start-Up Guide referenced below documents the SW 6 differences.
3. Currently loaded HMI language: read the value under Diagnose > IBN > Sprache (Diagnosis > Start-up > Language) before the change so you have a fallback to write down.
4. PLC backup state: ensure a current PLC program backup (S5-DOS file) and a current NCK initial/initial-clear backup are stored on a PG or a USB floppy, in case the language change requires a reset that wipes work offsets.
5. Password status: verify the OEM password 1111 is still active. If the OEM has been changed by the machine builder, contact the OEM for the current password before attempting the change.

Locating the Language Menu Path

The SINUMERIK 840C MMC exposes seven primary operating areas along its top-level horizontal soft-key bar:

The language setting is not on the top-level bar. It is nested under the commissioning area, which itself is reached from the Diagnosis area. Operators new to the platform frequently stop at the top-level Diagnosis screen and conclude that no language selection exists, but the actual control is one level deeper in the IBN submenu.

Required Access Credentials

The Start-Up area on a SINUMERIK 840C MMC is access-protected. The four protection levels map as follows:

Use OEM password 1111 to access the IBN area and change the HMI language. The same password is used to enter IBN on most 840C builds; the OEM is permitted to change it during commissioning. If 1111 does not work, the OEM has changed it. In that case, do not attempt a brute-force sequence; instead, request the password from the machine builder, or perform an OEM cold start of the MMC using the OEM disk, which will reset the password to 1111 but will also reset other commissioning data.

Step-by-Step Language Change Procedure

1. Bring the machine to a safe state: cycle stop, program end, and confirm NC READY is not required. The change can be performed while the machine is idle; do not perform it during a part program execution.
2. Switch the MMC key switch to position 0 (or to the position that allows HMI access; on most 840C installations the MMC key switch is independent of the NCK key switch).
3. On the MMC, press the horizontal soft key labelled Diagnose (in German HMI: Diagnose). The Diagnosis area is typically the fifth or sixth soft key from the left; the exact order is fixed by the HMI software and does not change with the display language.
4. Press the vertical soft key labelled IBN (Inbetriebnahme / Start-up). If the IBN soft key is greyed out or the system prompts for a password, enter the OEM password 1111 on the numeric keypad and press Input.
5. Press the vertical soft key labelled Sprache (Language). A list of installed languages appears. Typical entries on a multilingual 840C are: Deutsch (D), English (GB), Français (F), Italiano (I), Español (E), and any additional packs the OEM installed.
6. Select English (GB) (or your target language) with the cursor and press the Input key. The HMI writes the language index to a non-volatile location on the MMC.
7. Press the horizontal soft key for the Machine area. The MMC does not switch language instantly; some labels update immediately, but most require a full MMC reboot to read the new language table.
8. Reboot the MMC. The standard method is to press the MMC reset button, or to power-cycle the MMC subsystem (NCK may remain powered). After reboot, the HMI starts in the selected language.

MMC Reboot Sequence

The 840C MMC is a separate sub-rack from the NCK. Three reboot options exist:

For a language change, the soft reset is sufficient. A full power cycle is not required and will unnecessarily require re-referencing all axes. After the soft reset, the HMI boot screen displays the selected language and the top-level operating areas appear in English.

Verification Procedure

After the MMC reboot completes, verify the change has taken effect across all operating areas:

1. The horizontal soft-key bar should read: Machine, Parameter, Program, Services, Diagnosis, .... The German default reads Maschine, Parameter, Programm, Dienste, Diagnose, ....
2. Open the Parameter area, press Tool Offset, and confirm that soft-key labels are in English (e.g., Length, Radius, Wear).
3. Open the Program area, select a part program, and press Edit. The editor should display English prompts such as Search, Replace, Mark Block.
4. Open the Diagnosis area, then Alarms. Alarm text and clear conditions should be in English.
5. Check the alarm log under Diagnosis > Alarm Log and confirm time-stamped entries from before the language change still display in their original language (the 840C stores alarm texts in the language active when the alarm was raised); only new alarms will appear in English. This is normal behavior on V5 and V6 software.
6. If any of the above does not update, repeat the procedure: re-enter IBN with password 1111, re-select English, and perform a second soft reset. If the change still does not persist, see the troubleshooting matrix below.

Version-Specific Behavior

Troubleshooting Matrix

Edge Cases and Field Notes

Single-language MMC: Some OEMs ship the 840C MMC with only one language disk installed to reduce licensing cost. In this case, the Sprache menu under IBN either is hidden or shows only one selectable entry. Attempting to select a non-installed language will return an error such as Sprache nicht vorhanden (language not present). The remedy is to obtain the appropriate HMI language pack disk from Siemens or the OEM and install it via the MMC disk drive using the Dienste > Daten I/O (Services > Data I/O) menu.

Battery-backed language loss: The 840C MMC stores the language index in battery-backed SRAM. When the lithium battery on the MMC card fails (typical service life 5 to 10 years, depending on operating temperature), the MMC reverts to German on next power-up. The language change procedure above re-stores the index in backed-up RAM. If the language reverts repeatedly, replace the battery.

Backup-restore override: A PLC or NCK backup restore on a 840C with SW 5 or higher writes the language index from the backup image to the MMC NVRAM. If you back up a machine in English and restore to a machine that was previously in German, the restored language is English regardless of the current IBN setting. Plan language strategy as part of your backup policy.

840CE safety systems: On the 840CE variant, the Safety Programmable Logic (SPL) runs on a separate partition. The SPL must be in Stop state when changing the HMI language; otherwise the PLC stop command issued by the IBN procedure can fault the safety partition. Switch SPL to Stop from Diagnose > IBN > Safety before changing language, then return SPL to Run after the MMC reboot.

OEM custom screens: Many machine builders (Index, Gildemeister, Boehringer, Mazak retrofit) authored custom HMI screens in German that are stored in the OEM project file. The Sprache switch under IBN does not translate these screens. If your machine shows mixed German/English after the change, the German strings are coming from the OEM project. The fix requires editing the OEM project on a Siemens PG and reloading the MMC.

Password recovery risk: Resetting the OEM password by clearing the MMC battery will erase settable G functions, R parameters, and active NCK data. Always store a fresh PLC/NCK backup on a programming device (PG) before performing any password reset.

From SW 4 to SW 6 migration: Operators upgrading a 840C from SW 4 to SW 6 (an OEM-supported upgrade) will find the IBN > Sprache path unchanged, but the language table format and font handling differ. The OEM Start-Up Guide documents the SW 4 to SW 6 differences and is the authoritative reference.

Related Siemens Documentation

The OEM Start-Up Guide for SINUMERIK 840C SW 6 is the primary reference for the commissioning, language, and password changes described in this article. It is published as a PDF attachment on the Siemens Industry Online Support portal and can be downloaded directly. Operators performing the language change for the first time should keep this document open alongside the procedure.

For SW 4 and SW 5 environments, the operator's guide and programming manual from the machine builder (Index, Gildemeister, etc.) provide the same path but with version-specific screen captures. These documents are typically delivered with the machine and are not always available on the Siemens public portal.