G82 spot drilling with dwell in CNC Programming

Introduction

G82 is used in CNC machines to drill a hole and pause briefly at the bottom. This pause helps make a clean, precise hole.

When you need to drill holes that require a pause to clear chips or improve hole quality.

When drilling deep holes where the drill bit needs to stop briefly to reduce heat.

When making holes in soft materials that might deform without a dwell.

When you want to ensure the drill bit fully penetrates before retracting.

Syntax

CNC Programming

G82 X__ Y__ Z__ R__ P__ F__

X and Y specify the hole position.

Z is the depth to drill.

R is the retract height above the part.

P is the dwell time in seconds (pause at bottom).

F is the feed rate (speed of drilling).

Examples

Drill at X=10, Y=20 to depth -5mm, retract to 1mm above surface, pause 2 seconds, feed rate 100.

CNC Programming

G82 X10 Y20 Z-5 R1 P2 F100

Drill at origin to 3mm depth, retract 0.5mm, dwell 1 second, slower feed rate 50.

CNC Programming

G82 X0 Y0 Z-3 R0.5 P1 F50

Sample Program

This program moves the drill to position X15 Y25, drills down 6mm, pauses 3 seconds at the bottom, then retracts. G80 cancels the cycle after drilling.

CNC Programming

O1000 (Spot Drilling Example)
G90 G94 G17 (Absolute positioning, feed per minute, XY plane)
G21 (Units in mm)
G00 X0 Y0 (Move to start position)
G82 X15 Y25 Z-6 R1 P3 F120 (Spot drill at X15 Y25, 6mm deep, retract 1mm, dwell 3 seconds, feed 120)
G80 (Cancel canned cycle)
M30 (End program)

Important Notes

Always use G80 to cancel the canned cycle after finishing spot drilling.

Dwell time (P) is important to get clean holes and avoid tool damage.

Make sure retract height (R) is set safely above the workpiece to avoid collisions.

Summary

G82 drills holes with a pause at the bottom for better hole quality.

Use X, Y for position, Z for depth, R for retract height, P for dwell time, and F for feed rate.

Always cancel with G80 after using G82.

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