Canned drilling cycles save enormous programming time — but forgetting to cancel them is one of the most common silent CNC disasters. Many programmers assume the cycle ends automatically.
It does not.
This guide explains why forgetting G80 causes unexpected drilling motion.
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1) What Happens Without G80
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If G81/G83 remains active:
Every XY move becomes another drilling command.
Machine may suddenly plunge.
Example:
G81 Z-20 R2 F200
X100 Y50
Later:
G00 X200 Y80
Machine drills again unexpectedly.
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2) The Operator Shock Moment
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Rapid move expected.
Tool plunges suddenly.
Fixture collision possible.
Most believe machine malfunctioned.
Reality:
Cycle never canceled.
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3) Restart Risk
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Restart inside drilling section.
Cycle remains active.
Unexpected plunge.
Always restart before canned cycle activation.
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4) Tool Change Disaster
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Tool changed.
Cycle still active.
Next XY motion drills with wrong tool.
Catastrophic result.
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5) Professional Programming Pattern
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Always cancel cycles explicitly:
G80
Never assume automatic cancellation.
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6) Automation Consideration
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Lights-out machining demands deterministic state.
Hidden canned cycles destroy automation reliability.
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7) Final Takeaway
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Canned cycles are powerful.
Uncancelled canned cycles are dangerous.
Always end drilling logic clearly.
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