G82 spot drilling with dwell in CNC Programming - Step-by-Step Execution

Concept Flow - G82 spot drilling with dwell

Start Program

↓

Move to XY position

↓

Activate G82 cycle

↓

Drill down to Z depth

↓

Dwell (pause) for set time

↓

Retract drill to safe height

↓

Move to next position or end

The G82 cycle moves the drill to a position, drills down, pauses (dwells), then retracts before moving on.

Execution Sample

CNC Programming

N10 G90 G54
N20 G00 X10 Y10
N30 G82 Z-5 R1 P2 F100
N40 G80
N50 M30

This program moves to X10 Y10, performs a spot drill to Z-5 with 2 seconds dwell, then cancels the cycle.

Execution Table

Step	Command	Action	Position (X,Y,Z)	Dwell Time (P)	Output
1	G90 G54	Set absolute mode and work offset	(0,0,0)	0	Ready for positioning
2	G00 X10 Y10	Rapid move to XY position	(10,10,0)	0	Positioned at drill spot
3	G82 Z-5 R1 P2 F100	Start spot drilling cycle	(10,10,0)	2 seconds	Drill down to Z-5
4	Drill down	Feed drill to Z-5	(10,10,-5)	2 seconds	At drilling depth
5	Dwell	Pause drill for 2 seconds	(10,10,-5)	2 seconds	Dwell complete
6	Retract	Retract drill to R plane (Z=1)	(10,10,1)	0	Retracted to safe height
7	G80	Cancel canned cycle	(10,10,1)	0	Cycle cancelled
8	M30	End program	(10,10,1)	0	Program ended

💡 Program ends after M30 command

Variable Tracker

Variable	Start	After Step 2	After Step 4	After Step 6	Final
X	0	10	10	10	10
Y	0	10	10	10	10
Z	0	0	-5	1	1
Dwell Time (P)	0	0	2	0	0
Cycle Active	No	No	Yes	No	No

Key Moments - 3 Insights

Why does the drill retract to R plane after dwelling?

After dwelling at the drilling depth (step 5), the drill must retract to the R plane (step 6) to avoid dragging on the workpiece when moving.

What happens if G80 is not used after G82?

Without G80 (step 7), the spot drilling cycle remains active and may repeat unintentionally on subsequent moves.

Why is the dwell time important in G82?

The dwell time (P parameter) pauses the drill at the bottom to ensure a clean spot drill hole, as shown in step 5.

Visual Quiz - 3 Questions

Look at the execution table, what is the Z position after the drill retracts?

A 0

B -5

C 1

D 10

💡 Hint

Check Step 6 in the execution table under Position (X,Y,Z)

At which step does the drill pause for the dwell time?

A Step 3

B Step 5

C Step 4

D Step 6

💡 Hint

Look for the 'Dwell' action in the execution table

If the P parameter is changed from 2 to 0, what changes in the execution?

A The drill will not dwell at the bottom

B The drill will retract immediately after moving to XY

C The drill will drill deeper

D The program will end early

💡 Hint

Refer to the Dwell Time (P) column in the execution table

Concept Snapshot

G82 spot drilling cycle:
- Moves drill to XY
- Drills down to Z depth
- Dwells (pauses) for P seconds
- Retracts to R plane
- Use G80 to cancel cycle
Dwell ensures clean spot drill holes.

Full Transcript

This visual execution trace shows how the G82 spot drilling cycle works. The program starts by setting absolute mode and work offset. It moves rapidly to the XY position where drilling will occur. The G82 command activates the spot drilling cycle, drilling down to the specified Z depth. Then the drill pauses, or dwells, for the time set by the P parameter to ensure a clean hole. After dwelling, the drill retracts to the R plane to avoid dragging. The G80 command cancels the cycle, and the program ends with M30. Variables like X, Y, Z positions and dwell time change step-by-step, helping beginners see how the drill moves and pauses during the cycle.

Practice

1. What is the main purpose of the G82 command in CNC programming?

easy

A. To set the spindle speed

B. To move the tool rapidly without cutting

C. To perform spot drilling with a dwell pause at the bottom of the hole

D. To cancel all canned cycles

Solution

1. Step 1: Understand the function of G82

   G82 is used for spot drilling, which means drilling with a pause (dwell) at the bottom to improve hole quality.

2. Step 2: Compare with other options

   Other options describe different commands: rapid move (G0), cancel cycle (G80), spindle speed (S code), so they are incorrect.

3. Final Answer:

   To perform spot drilling with a dwell pause at the bottom of the hole -> Option C

4. Quick Check:

   G82 = Spot drilling with dwell [OK]

Hint: G82 always drills with a pause at the bottom [OK]

Common Mistakes:

• Confusing G82 with G80 (cancel cycle)
• Thinking G82 is for rapid moves
• Mixing G82 with spindle speed commands

2. Which of the following is the correct syntax for a G82 spot drilling cycle with a dwell time of 2 seconds at position X10 Y5 and depth Z-5?

easy

A. G82 X10 Y5 Z-5 F100 P2 R1

B. G82 X10 Y5 Z-5 P2 R1 F100

C. G82 X10 Y5 Z-5 R1 F100

D. G82 X10 Y5 Z-5 R1 P2 F100

Solution

1. Step 1: Identify correct parameter order for G82

   The standard order is: G82 X Y Z R P F where R is retract height, P is dwell time, F is feed rate.

2. Step 2: Check each option

   G82 X10 Y5 Z-5 R1 P2 F100 follows correct order and includes all required parameters. Options A and B swap P and R order, which may cause errors. G82 X10 Y5 Z-5 R1 F100 misses P (dwell time).

3. Final Answer:

   G82 X10 Y5 Z-5 R1 P2 F100 -> Option D

4. Quick Check:

   Correct G82 syntax = G82 X10 Y5 Z-5 R1 P2 F100 [OK]

Hint: Remember order: X Y Z R (retract) P (pause) F (feed) [OK]

Common Mistakes:

• Swapping P and R parameters
• Omitting dwell time P
• Incorrect parameter order causing syntax errors

3. What will be the tool behavior for the following CNC code snippet?

G82 X20 Y10 Z-8 R2 P3 F80
G80

medium

A. The tool moves rapidly to X20 Y10 without drilling

B. The tool drills to Z-8 at X20 Y10, dwells 3 seconds, retracts to 2, then cancels cycle

C. The tool drills to Z-8 without dwell and retracts to 3

D. The tool drills to Z-8, dwells 2 seconds, retracts to 3, then cancels cycle

Solution

1. Step 1: Interpret G82 parameters

   X20 Y10 is position, Z-8 is drill depth, R2 is retract height, P3 is dwell time in seconds, F80 is feed rate.

2. Step 2: Understand G80 effect

   G80 cancels canned cycles after G82 completes.

3. Final Answer:

   The tool drills to Z-8 at X20 Y10, dwells 3 seconds, retracts to 2, then cancels cycle -> Option B

4. Quick Check:

   G82 drills with dwell and retract, G80 cancels cycle [OK]

Hint: P is dwell seconds, R is retract height in G82 [OK]

Common Mistakes:

• Confusing R and P values
• Ignoring G80 cancels cycle
• Assuming no dwell happens

4. Identify the error in this G82 spot drilling command:

G82 X15 Y10 Z-6 P2 F100

medium

A. Missing retract height (R) parameter

B. Dwell time (P) cannot be used with G82

C. Feed rate (F) must come before Z depth

D. X and Y coordinates are not allowed with G82

Solution

1. Step 1: Check required parameters for G82

   G82 requires R (retract height) to know how far to pull up after drilling.

2. Step 2: Analyze given command

   The command lacks R parameter, so the machine won't know retract height, causing error.

3. Final Answer:

   Missing retract height (R) parameter -> Option A

4. Quick Check:

   G82 needs R parameter for retract [OK]

Hint: Always include R (retract) with G82 [OK]

Common Mistakes:

• Omitting R parameter
• Misplacing feed rate F
• Thinking dwell P is optional

5. You want to drill three holes at positions X5 Y5, X10 Y5, and X15 Y5 using G82 with a dwell of 1.5 seconds, depth Z-4, retract height R1, and feed rate F60. Which of the following code snippets correctly applies G82 for all three holes and cancels the cycle afterward?

hard

A. G82 X5 Y5 Z-4 R1 P1.5 F60\nG82 X10 Y5 Z-4 R1 P1.5 F60\nG82 X15 Y5 Z-4 R1 P1.5 F60\nG80

B. G82 X5 Y5 Z-4 R1 P1.5 F60\nG82 X10 Y5\nG82 X15 Y5\nG80

C. G82 X5 Y5 Z-4 R1 P1.5 F60\nX10 Y5\nX15 Y5\nG80

D. G82 X5 Y5 Z-4 R1 P1.5 F60\nG80\nG82 X10 Y5 Z-4 R1 P1.5 F60\nG82 X15 Y5 Z-4 R1 P1.5 F60

Solution

1. Step 1: Understand G82 cycle behavior

   G82 must be repeated with full parameters for each hole position unless modal commands are supported, which is not guaranteed.

2. Step 2: Analyze each option

   G82 X5 Y5 Z-4 R1 P1.5 F60\nG82 X10 Y5\nG82 X15 Y5\nG80 repeats G82 but omits parameters for second and third holes, which may cause errors. G82 X5 Y5 Z-4 R1 P1.5 F60\nX10 Y5\nX15 Y5\nG80 lacks G82 before second and third holes. G82 X5 Y5 Z-4 R1 P1.5 F60\nG80\nG82 X10 Y5 Z-4 R1 P1.5 F60\nG82 X15 Y5 Z-4 R1 P1.5 F60 cancels cycle (G80) too early. G82 X5 Y5 Z-4 R1 P1.5 F60\nG82 X10 Y5 Z-4 R1 P1.5 F60\nG82 X15 Y5 Z-4 R1 P1.5 F60\nG80 repeats full G82 command for each hole and cancels cycle at end, which is correct.

3. Final Answer:

   G82 X5 Y5 Z-4 R1 P1.5 F60 G82 X10 Y5 Z-4 R1 P1.5 F60 G82 X15 Y5 Z-4 R1 P1.5 F60 G80 -> Option A

4. Quick Check:

   Repeat full G82 per hole, then G80 to cancel [OK]

Hint: Repeat full G82 for each hole, then end with G80 [OK]

Common Mistakes:

• Omitting parameters on repeated G82 lines
• Cancelling cycle too early with G80
• Assuming parameters carry over without repetition