G82 spot drilling with dwell in CNC Programming - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the G82 command do in CNC programming?

G82 is used for spot drilling with a dwell time at the bottom of the hole to ensure a precise and clean spot before retracting.

beginner

Why is dwell time important in G82 spot drilling?

Dwell time allows the drill to pause at the bottom of the hole, helping to create a clean and accurate spot without wandering or deflection.

intermediate

Which parameters are typically included in a G82 command?

The G82 command usually includes the X, Y coordinates for the hole position, Z depth for drilling, feed rate (F), retract height (R), and dwell time (P).

intermediate

How does G82 differ from G81 drilling cycle?

G81 drills holes without dwell time, moving directly up after reaching the depth, while G82 pauses at the bottom for a set dwell time before retracting.

intermediate

Example: What does this line do? G82 X10 Y20 Z-5 R1 F100 P2

It drills a spot at X=10, Y=20 to a depth of -5 units, retracts to R=1 unit above the surface, feeds at 100 units/min, and dwells for 2 seconds at the bottom.

What is the main purpose of the dwell time in G82?

A To pause at the hole bottom for a clean spot

B To increase spindle speed

C To move faster between holes

D To cool the drill bit

Dwell time pauses the drill at the hole bottom to create a precise spot before retracting.

Which parameter in G82 sets the dwell time?

A F

B R

C Z

D P

The P parameter specifies the dwell time in seconds in the G82 command.

What happens if you use G81 instead of G82 for spot drilling?

A The drill will dwell longer

B The drill will retract slower

C The drill will not dwell at the hole bottom

D The drill will drill deeper

G81 drills without dwell, so it does not pause at the hole bottom like G82.

In G82, what does the R parameter control?

A Feed rate

B Retract height above the surface

C Dwell time

D Drill speed

R sets the retract height above the surface where the drill stops before moving to the next hole.

Which of these is a correct G82 command format?

A G82 X10 Y20 Z-5 R1 F100 P2

B G82 X10 Y20 Z5 R1 F100 P2

C G82 X10 Y20 Z-5 F100 R1 P2

D G82 X10 Y20 R1 Z-5 F100

The correct order includes coordinates, depth (negative for drilling down), retract height, feed rate, and dwell time.

Explain how the G82 spot drilling cycle works and why dwell time is used.

Think about what happens when the drill reaches the hole bottom.

List the key parameters in a G82 command and describe what each controls.

Consider the position, depth, speed, and pause in the drilling 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