Canned cycle cancel (G80) in CNC Programming - Step-by-Step Execution

Concept Flow - Canned cycle cancel (G80)

Start Program

↓

Activate Canned Cycle (e.g., G81)

↓

Perform Drilling Cycle

↓

Issue G80 to Cancel Cycle

↓

Return to Normal Motion

↓

Continue with Next Commands or End

The flow shows starting a canned cycle, performing it, then using G80 to cancel it and return to normal motion.

Execution Sample

CNC Programming

N10 G81 X10 Y10 Z-5 R1 F100
N20 G80
N30 G00 X0 Y0

This CNC program drills at X10 Y10 with G81, then cancels the canned cycle with G80, and moves to X0 Y0.

Execution Table

Step	Command	Action	Cycle Active	Machine Motion
1	N10 G81 X10 Y10 Z-5 R1 F100	Start drilling canned cycle	Yes (G81 active)	Drilling cycle at X10 Y10: rapid to Z1 (R), feed to Z-5, rapid to Z1
2	N20 G80	Cancel canned cycle	No (G80 cancels cycle)	No motion, cycle cancelled
3	N30 G00 X0 Y0	Rapid move to X0 Y0	No	Rapid move to X0 Y0 position

💡 G80 cancels the active canned cycle, so subsequent moves are normal machine motions.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3
Cycle Active	No	Yes (G81 active)	No (G80 cancels)	No
Machine Position	(unknown)	X10 Y10 Z1 (R-plane, cycle complete)	X10 Y10 Z1 (R-plane, cycle cancelled)	X0 Y0 Z1

Key Moments - 2 Insights

Why does the machine stop drilling after G80 even though no new position is given?

Because G80 cancels the canned cycle (see execution_table step 2), stopping the drilling cycle and returning to normal motion.

What happens if G80 is not used after a canned cycle?

The machine will repeat the canned cycle for subsequent moves, which may cause unintended drilling or machining (implied by cycle active state in variable_tracker).

Visual Quiz - 3 Questions

Look at the execution table, what is the cycle active state after step 2?

A Yes, canned cycle is still active

B No, canned cycle is cancelled

C Partially active

D Unknown

💡 Hint

Check the 'Cycle Active' column at step 2 in the execution_table.

At which step does the machine perform a rapid move to a new position?

A Step 1

B Step 2

C Step 3

D No rapid move occurs

💡 Hint

Look at the 'Machine Motion' column in the execution_table for step 3.

If G80 was omitted, what would happen to the 'Cycle Active' variable after step 2?

A It would remain 'Yes' (active)

B It would become 'No' (cancelled)

C It would toggle between Yes and No

D It would cause an error

💡 Hint

Refer to the variable_tracker and understand that G80 cancels the cycle.

Concept Snapshot

G80 cancels any active canned cycle.
Use G80 after cycles like G81 to stop repeated machining.
Without G80, the machine repeats the cycle.
After G80, machine moves normally.
Syntax example: N20 G80 cancels cycle.

Full Transcript

This lesson shows how the G80 command cancels canned cycles in CNC programming. The flow starts with activating a canned cycle like G81 to drill at a position. Then G80 is issued to cancel the cycle, stopping repeated drilling. Finally, normal machine moves continue. The execution table traces each step: starting the cycle, cancelling it, and moving rapidly. Variables track if the cycle is active and the machine position. Key points clarify why G80 stops drilling and what happens if omitted. Quiz questions check understanding of cycle state and machine motion. The snapshot summarizes G80 usage and effects.

Practice

1. What is the main purpose of the G80 command in CNC programming?

easy

A. To start a drilling cycle

B. To set the spindle speed

C. To cancel any active canned cycle

D. To move the tool to the home position

Solution

1. Step 1: Understand what a canned cycle is

   Canned cycles automate repetitive machining tasks like drilling or milling.

2. Step 2: Identify the role of G80

   G80 cancels any active canned cycle to return to normal movement commands.

3. Final Answer:

   To cancel any active canned cycle -> Option C

4. Quick Check:

   G80 cancels canned cycles = B [OK]

Hint: G80 always stops canned cycles safely [OK]

Common Mistakes:

• Thinking G80 starts a cycle
• Confusing G80 with spindle control
• Assuming G80 moves the tool

2. Which of the following is the correct syntax to cancel a canned cycle in CNC code?

easy

A. G81

B. G80

C. M30

D. G90

Solution

1. Step 1: Recall common G-codes for canned cycles

   G81 starts a drilling cycle, G90 sets absolute positioning, M30 ends the program.

2. Step 2: Identify the cancel command

   G80 is the standard code to cancel any active canned cycle.

3. Final Answer:

   G80 -> Option B

4. Quick Check:

   Cancel canned cycle = G80 = A [OK]

Hint: G80 is the cancel code, not G81 or M30 [OK]

Common Mistakes:

• Using G81 instead of G80
• Confusing M30 with cycle cancel
• Mixing positioning codes with cycle cancel

3. Given the CNC program snippet:

G81 X10 Y10 Z-5 R1 F100
G80
G00 X0 Y0

What will the G80 command do here?

medium

A. Cancel the drilling cycle started by G81

B. Move the tool rapidly to X10 Y10

C. Start a drilling cycle at X0 Y0

D. Set feed rate to 80

Solution

1. Step 1: Analyze the G81 command

   G81 starts a drilling canned cycle at X10 Y10 with depth Z-5.

2. Step 2: Understand the effect of G80

   G80 cancels the active canned cycle, stopping the drilling cycle.

3. Final Answer:

   Cancel the drilling cycle started by G81 -> Option A

4. Quick Check:

   G80 cancels G81 cycle = C [OK]

Hint: G80 always cancels previous canned cycles like G81 [OK]

Common Mistakes:

• Thinking G80 starts a cycle
• Confusing G80 with rapid move
• Misreading feed rate as cycle cancel

4. Identify the error in this CNC code snippet:

G81 X20 Y20 Z-10 F150
G00 X0 Y0
G80

medium

A. No error; code is correct

B. G00 cannot be used after G81

C. G80 must be used immediately after G81 to cancel

D. G80 should come before G00 move

Solution

1. Step 1: Understand the order of commands

   G81 starts drilling; G80 cancels it. Moves like G00 should happen after cancel.

2. Step 2: Check the code sequence

   Here, G00 rapid move happens before G80 cancels the cycle, which can cause unexpected behavior.

3. Final Answer:

   G80 should come before G00 move -> Option D

4. Quick Check:

   Cancel cycle before moves = A [OK]

Hint: Always cancel canned cycles before rapid moves [OK]

Common Mistakes:

• Placing G80 after moves
• Assuming G00 cancels cycles
• Ignoring command order importance

5. You have a CNC program that drills multiple holes using G81. After finishing, you want to safely move the tool to a new position without drilling. Which sequence correctly cancels the drilling cycle and moves the tool?

hard

A. G81 X30 Y30 Z-5 F120
G80
G00 X50 Y50

B. G00 X50 Y50
G81 X30 Y30 Z-5 F120
G80

C. G80
G81 X30 Y30 Z-5 F120
G00 X50 Y50

D. G81 X30 Y30 Z-5 F120
G00 X50 Y50
G80

Solution

1. Step 1: Recognize the need to cancel the drilling cycle

   After drilling with G81, G80 must be used to cancel the cycle before moving.

2. Step 2: Check the sequence of commands

   G81 X30 Y30 Z-5 F120 G80 G00 X50 Y50 cancels the cycle with G80 before moving rapidly with G00, which is correct.

3. Final Answer:

   G81 X30 Y30 Z-5 F120 G80 G00 X50 Y50 -> Option A

4. Quick Check:

   Cancel cycle then move = D [OK]

Hint: Cancel cycle (G80) before moving tool (G00) [OK]

Common Mistakes:

• Moving tool before canceling cycle
• Starting new cycle before cancel
• Placing G80 before starting cycle