This is a complete, real-world CNC error encyclopedia created from the most common problems searched by CNC programmers, operators, and engineers worldwide. These are not theoretical mistakes. Every error listed here has caused real machine crashes, broken tools, scrapped parts, and lost production time. This guide is designed to remain relevant for years because CNC errors do not change — only machines get faster and more expensive.
SECTION 1: THE MOST COMMON CNC ALARM CODES (REAL)
FANUC ALARMS (MOST SEARCHED)
- 500 / 501 / 502 – Program or parameter protect enabled
Cause: Attempting to edit protected programs or offsets
Fix: Disable PWE or program protect before editing - 401 / 402 – Illegal G-code or M-code
Cause: Unsupported or misspelled code
Fix: Verify control version and syntax - 414 – Illegal axis command
Cause: Axis commanded beyond machine limits
Fix: Check G00 / G01 moves and soft limits - 086 – Overtravel alarm
Cause: Axis exceeded stroke limit
Fix: Use G22/G23 correctly and verify work offsets
HAAS ALARMS (MOST SEARCHED)
- Alarm 102 – Overtravel detected
Cause: Incorrect G54 or G00 Z move
Fix: Verify Z offset and safe retract height - Alarm 144 – Spindle orientation fault
Cause: Tool change or rigid tapping failure
Fix: Check spindle encoder and orientation M-codes - Alarm 160 – Tool not clamped
Cause: Tool change interrupted or air pressure issue
Fix: Check drawbar pressure and M06 sequence
SIEMENS ALARMS (MOST SEARCHED)
- 14000 – Axis position error
Cause: Servo lag or aggressive acceleration
Fix: Reduce feed, check servo tuning - 300500 – Program block error
Cause: Syntax or logical programming mistake
Fix: Check block structure and modal conflicts
SECTION 2: THE DEADLIEST G-CODE MISTAKES (REAL)
1) G00 Z-100 (THE MOST VIRAL CNC MISTAKE)
Why it is dangerous:
G00 is RAPID motion.
Z-100 means “go DOWN immediately”.
Real crash scenario:
Operator assumes G54 Z0 is set.
Z offset is wrong.
Machine rapids directly into vise or part.
Correct safe pattern:
G00 Z100.
G00 X…
G00 Y…
G01 Z…
Rule:
NEVER rapid into negative Z unless 100% verified.
2) Forgetting G90 / G91 State
Problem:
Program assumes absolute mode.
Machine is in incremental mode.
Result:
Tool moves relative instead of absolute.
Instant crash.
Best practice:
Always declare:
G90 G17 G40 G49 G80 at program start.
3) Missing G43 H Command
Problem:
Tool length offset not activated.
Result:
Tool moves to incorrect Z height.
Crashes into part.
Correct usage:
G00 Z50.
G43 H01 Z5.
4) Using G53 Incorrectly
Problem:
G53 ignores work offsets.
Crash scenario:
G53 Z0 executed while G68 rotation or G54 active.
Rule:
Always cancel transformations before G53:
G69
G53 Z0
SECTION 3: THE MOST COMMON CNC CRASH PATTERNS
- Tool change without Z retract
- Wrong tool number with correct H offset
- Copy-paste programs without checking offsets
- Assuming probe values without verification
- Running metric program on inch machine
- Missing G80 after drilling cycles
- Using G02/G03 with wrong I/J sign
- Running 5-axis code on 3-axis machine
- Running CAM post for wrong control
SECTION 4: CRASH-PROOF PROGRAMMING RULES
Rule 1:
Every program must start with a safety line:
G90 G17 G40 G49 G80 G94
Rule 2:
Never trust previous offsets.
Verify G54/G55 every setup.
Rule 3:
Always dry-run with:
- Single block
- Feed override 5–10%
- Z offset raised
Rule 4:
Never assume CAM is correct.
CAM generates motion, not safety.
Rule 5:
If unsure → STOP.
A stopped machine is cheaper than a crash.
SECTION 5: WHY THIS CONTENT STAYS VIRAL
- CNC errors are universal
- New programmers search these daily
- Experienced machinists still make these mistakes
- Machines get faster → crashes get worse
- Training never ends in CNC
This content answers:
“What went wrong?”
“Why did my machine crash?”
“How do I prevent it forever?”
FINAL SUMMARY
This CNC Error Encyclopedia is built from real production failures, real alarm codes, and real programming mistakes that happen every day across Fanuc, Haas, and Siemens machines. It is designed to be bookmarked, shared, referenced, and revisited continuously. As long as CNC machines exist, these errors will be searched — making this content a permanent traffic engine.
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