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Siemens SINUMERIK Controller
Program/G-code · Basic · 10 - 30 minutes
Siemens 18005 - Block serious error in definition of NCK-specific protection zone
SIEMENS alarm 18005 fires when the pneumatic pressure monitoring input configured in the PLC safety chain detects pressure below the minimum threshold set in machine data. This safety interlock prevents operations requiring adequate air pressure such as workholding, tool changes, and axis purging from executing without sufficient pneumatic supply.
18005
Siemens 18005 - Block serious error in definition of NCK-specific protection zone
Block serious error in definition of NCK-specific protection zone
Siemens SINUMERIK alarm 18005: Block serious error in definition of NCK-specific protection zone. Detailed remedy is being verified against the current Siemens diagnostics manual.
Root Cause Summary
SIEMENS alarm 18005 fires when the pneumatic pressure monitoring input configured in the PLC safety chain detects pressure below the minimum threshold set in machine data. This safety interlock prevents operations requiring adequate air pressure such as workholding, tool changes, and axis purging from executing without sufficient pneumatic supply.
Safety
- Only qualified personnel should diagnose and clear control alarms; follow the machine builder's safety procedures and lockout/tagout where hardware work is required.
Causes and Fixes
- 1
Check Main Air Supply
Verify compressor output pressure at main regulator. Standard CNC pneumatic systems require 6-8 bar (87-116 PSI) minimum.
Ensure LOTO procedures before checking pneumatic connections
- 2
Inspect Distribution System
Check all pneumatic filters, regulators, and distribution manifolds for proper pressure regulation and flow capacity.
Look for water accumulation in filter bowls which reduces effective flow
- 3
Verify Pressure Switch Setting
Access HMI Diagnostics > PLC > Inputs and verify pressure switch input state matches actual system pressure reading.
Pressure switch hysteresis typically set 0.5-1.0 bar below normal operating pressure
Call a technician if:
- ·Safety PLC programming changes required
- ·Pressure transducer calibration needed
- ·Major pneumatic component replacement
Prevention
- Regular pneumatic filter maintenance and water drainage
- Monthly pressure switch calibration verification
- Quarterly pneumatic system leak inspection
Common Mistakes
- Adjusting pressure switch setpoint without updating PLC parameters
- Ignoring gradual pressure decay indicating developing leaks
- Bypassing safety interlocks instead of fixing root cause
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Always verify with your machine manual or a certified technician before performing service procedures.