126-0116

Access PLC service mode

Press MOD key, enter service password, select 'PLC' to access the PLC programming and diagnostic environment. Navigate to the PLC program overview.

PLC modifications affect machine safety systems. Document all changes and ensure you have backup files before making any modifications.

Locate switch-off marker definitions

Search the PLC program for markers M4400 (NC switch-off signal) and M4401 (emergency stop feedback). These are typically found in the main safety logic section or initialization blocks of the PLC program.

Use the PLC search function (typically available in service mode) to quickly find all instances of M4400 and M4401 throughout the program.

Verify marker-to-output assignment

Check that M4400 is assigned to drive the appropriate physical output or internal signal that triggers NC shutdown. Verify the assignment matches the SIK.SYS configuration and machine electrical documentation.

Cross-reference with the machine electrical schematics to confirm the output number matches the physical relay or contactor controlling the NC power supply.

Test PLC logic compilation

After verifying or correcting assignments, compile the PLC program within the service mode to check for syntax errors or conflicts. The control will report any compilation issues that could cause the alarm.

Save the corrected PLC program with a new version number or date stamp for documentation and future reference.

Access system directory

In Programming and Editing mode, press 'PGM MGT' key, navigate to TNC:\system\ directory. Locate the SIK.SYS file (Safety I/O Configuration).

The system directory contains critical control files. Always create backups before modifying or replacing files in this directory.

Review SIK.SYS entries

Open SIK.SYS with the TNC text editor. Look for output definitions related to NC switch-off, typically labeled as 'NC_SWITCH_OFF' or similar. Verify the assigned I/O addresses match the machine's actual wiring.

Compare the SIK.SYS file with documentation from the machine tool builder. Different machine models may use different output assignments even with the same control.

Restore from backup if corrupted

If SIK.SYS shows obvious corruption (unreadable characters, incomplete lines), restore from a known-good backup located in TNC:\system\backup\ or from your service backup media.

If no backup exists, contact the machine tool builder for the original SIK.SYS file specific to your machine serial number and control software version.

Reboot and verify

After correcting or restoring SIK.SYS, perform a complete control reboot (power cycle) to force re-initialization of the PLC configuration with the corrected file.

Monitor the startup sequence and check the PLC status display to confirm the control properly loads the configuration without errors.

Generate PLC cross-reference

In PLC service mode, use the cross-reference function to generate a complete list of all outputs and where they are assigned. Look for the output designated for NC switch-off to see if it appears in multiple locations.

The cross-reference tool is typically accessed through the PLC menu under 'Documentation' or 'Cross-Reference' - specific path varies by control software version.