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Siemens SINUMERIK Controller
Program/G-code · Intermediate · 15-30 minutes
Siemens 14500 - Block illegal DEF or PROC instruction in the part program
SIEMENS alarm 14500 fires when the NCK calculates a contour element (line, arc, or spline) with a length smaller than the minimum traversing distance defined in MD20200 CONTOUR_TOL. This typically occurs from CAM post-processor issues generating micro-segments, excessive look-ahead preprocessing creating tiny interpolated moves, or incorrect machine data settings for contour tolerance.
14500
Siemens 14500 - Block illegal DEF or PROC instruction in the part program
Block illegal DEF or PROC instruction in the part program
Siemens SINUMERIK alarm 14500: Block illegal DEF or PROC instruction in the part program. Detailed remedy is being verified against the current Siemens diagnostics manual.
Root Cause Summary
SIEMENS alarm 14500 fires when the NCK calculates a contour element (line, arc, or spline) with a length smaller than the minimum traversing distance defined in MD20200 CONTOUR_TOL. This typically occurs from CAM post-processor issues generating micro-segments, excessive look-ahead preprocessing creating tiny interpolated moves, or incorrect machine data settings for contour tolerance.
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 Current MD20200 Setting
Access HMI → Commissioning → Machine Data → Channel-Specific → MD20200 CONTOUR_TOL to verify current minimum contour tolerance value.
Default value is typically 0.001mm - values below 0.0001mm often cause issues
- 2
Analyze Program Block Lengths
Use Program Manager → Edit Mode to examine G01/G02/G03 blocks around alarm occurrence, looking for coordinate changes smaller than MD20200 value.
Do not modify part program without consulting programmer - dimensional accuracy may be affected
- 3
Adjust CAM Chord Tolerance
Coordinate with programmer to increase CAM post-processor chord tolerance to generate larger minimum segment lengths, typically 2-3x the MD20200 value.
For finishing operations, balance surface quality requirements against minimum segment size
- 4
Implement COMPOF/COMPON Filtering
Add COMPOF before problematic contour sections and COMPON after to disable/enable contour monitoring temporarily if dimensional accuracy permits.
Only use as temporary solution - affects overall machining precision
Call a technician if:
- ·Servo system instability occurs after MD changes
- ·Multiple related alarms appear simultaneously
- ·OEM machine data backup is not available
Prevention
- Establish CAM post-processor standards with minimum segment lengths
- Regular backup of working machine data configurations
- Coordinate with programmers on contour tolerance requirements
Common Mistakes
- Setting MD20200 too small for encoder resolution
- Ignoring coordinate transformation effects on contour size
- Modifying machine data without testing on sample programs first
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