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Access PLC Program via SIMATIC Manager

Connect to the SINUMERIK system and open the PLC program to locate the maintenance counter data block (typically DB10-DB50 range for user data).

Look for DB names containing 'MAINT', 'SERVICE', or 'COUNTER' in the symbol table.

Check Spindle Hour Accumulator

Navigate to the maintenance DB and examine the spindle hours counter (usually REAL or DINT format) and compare against the preset limit value in the same block.

Do not modify counter values without performing actual maintenance.

Verify Through HMI Service Menu

Access Machine > Service > Maintenance Counters on the SINUMERIK HMI to view current spindle hours and remaining time until next service interval.

Some OEMs provide password-protected reset functions in custom HMI screens.

Reset Counter After Maintenance

After completing spindle maintenance, reset the counter through the PLC program or HMI service screen using the machine builder's prescribed procedure.

Check System Runtime Variables

Access Diagnostics > Service > NC Variables and examine $AC_OPERATING_TIME or similar system variables that track machine runtime hours.

SINUMERIK automatically maintains these counters in non-volatile memory.

Locate PLC Maintenance Logic

In the PLC program, find the organization block (typically OB1 or OB35) that compares runtime variables against maintenance thresholds stored in the machine DB.

Ensure PLC is in STOP mode before examining program logic online.

Verify Maintenance Schedule Parameters

Check the machine data block for maintenance interval settings (typically 500-2000 hour intervals) and confirm current accumulated hours.

Many OEMs store multiple maintenance levels (A, B, C service) with different hour thresholds.

Acknowledge and Reset After Service

Perform required maintenance tasks, then reset the appropriate counter bit or value in the PLC maintenance DB to clear the alarm condition.

Access Cycle Counter Variables

Navigate to Machine > Counters or check NC variables for part counters that may be linked to maintenance scheduling in the PLC program.

Look for variables like $AC_PARTS_TOTAL or custom R-parameters used for cycle counting.

Examine PLC Counter Logic

In the PLC program, locate the counter function blocks (CTU or CTUD) that increment with each cycle completion and trigger maintenance alarms.

Verify counter preset values match machine documentation before making changes.

Check Maintenance DB Thresholds

Review the maintenance data block for cycle-based service intervals and compare against current accumulated cycle count.

Some systems use multiple counters for different maintenance tasks (lubrication, tool changes, etc.).

Reset Counter Post-Maintenance

After completing required maintenance, reset the cycle counter through PLC program modification or HMI maintenance screen access.

Identify Custom Parameters

Review machine documentation and PLC symbol table to identify custom maintenance parameters specific to this machine configuration.

Check for parameters related to hydraulic cycles, pneumatic actuations, or thermal cycles.

Monitor Parameter Values Online

Use PLC online monitoring to observe custom parameter values in real-time and identify which specific parameter triggered the maintenance alarm.

Some parameters may reset automatically and require trend monitoring to identify.

Verify Against Maintenance Schedule

Cross-reference current parameter values with machine builder's maintenance schedule to confirm appropriate maintenance actions required.

Custom parameters often relate to consumable components with specific replacement intervals.

Perform Targeted Maintenance

Execute the specific maintenance procedure related to the custom parameter and reset the appropriate counter or flag in the PLC maintenance logic.