G02 clockwise arc in CNC Programming - Step-by-Step Execution

Concept Flow - G02 clockwise arc

Start at current position

↓

Read G02 command

↓

Identify end point (X,Y)

↓

Identify center offset (I,J)

↓

Calculate clockwise arc path

↓

Move tool along arc to end point

↓

Update current position to end point

↓

Wait for next command

The CNC machine reads the G02 command, calculates the clockwise arc path using the end point and center offsets, then moves the tool along this arc.

Execution Sample

CNC Programming

G90 G02 X10 Y0 I5 J0 F100

Moves the tool in a clockwise arc from current position to X=10, Y=0 with center offset I=5, J=0 at feed rate 100.

Execution Table

Step	Action	Value/Calculation	Result/Position
1	Start at current position	X=0, Y=0	Position: (0,0)
2	Read command	G02 X10 Y0 I5 J0 F100	Prepare clockwise arc move
3	Calculate center	Center = Current + (I,J) = (0+5, 0+0)	Center at (5,0)
4	Calculate arc path	Clockwise arc from (0,0) to (10,0) around center (5,0)	Arc path defined
5	Move tool along arc	Feed rate 100	Tool moves clockwise along arc
6	Update position	End point X=10, Y=0	Position updated to (10,0)
7	Wait for next command	-	Ready for next instruction

💡 End point reached, arc move complete, ready for next command

Variable Tracker

Variable	Start	After Step 3	After Step 6
X	0	0	10
Y	0	0	0
I	-	5	5
J	-	0	0
Position	(0,0)	(0,0)	(10,0)
Center	-	(5,0)	(5,0)

Key Moments - 3 Insights

Why do we add I and J to the current position to find the center?

Because I and J represent the offset from the current position to the arc's center, as shown in step 3 of the execution_table.

How do we know the tool moves clockwise and not counterclockwise?

The G02 command specifically instructs a clockwise arc move, which is why in step 4 the arc path is calculated clockwise.

What happens if the end point is the same as the start point?

The arc would be a full circle around the center; the execution_table would show the same start and end positions but the tool moves along the full arc.

Visual Quiz - 3 Questions

Look at the execution_table, what is the center position after step 3?

A (0,0)

B (5,0)

C (10,10)

D (0,5)

💡 Hint

Check the 'Calculate center' row in the execution_table.

At which step does the tool position update to the end point?

A Step 4

B Step 5

C Step 6

D Step 7

💡 Hint

Look for 'Update position' action in the execution_table.

If the I value changed from 5 to 3, how would the center position change after step 3?

A (3,0)

B (5,0)

C (0,3)

D (0,0)

💡 Hint

Center is current position plus I and J offsets as shown in variable_tracker.

Concept Snapshot

G02 command moves tool in a clockwise arc.
Syntax: G02 X[end] Y[end] I[offsetX] J[offsetY] F[feedrate]
I and J are offsets from current position to arc center.
Tool moves from current to end point along clockwise arc.
Feedrate controls speed of movement.

Full Transcript

The G02 command in CNC programming tells the machine to move the tool in a clockwise arc from its current position to a specified end point. The arc's center is found by adding the I and J offsets to the current position. The machine calculates the arc path and moves the tool along it at the given feed rate. After the move, the current position updates to the end point, ready for the next command.

Practice

1. What does the G02 command do in CNC programming?

easy

A. Stops the tool movement immediately

B. Moves the tool in a straight line to a specified point

C. Moves the tool in a counterclockwise arc to a specified point

D. Moves the tool in a clockwise arc to a specified point

Solution

1. Step 1: Understand the G02 command purpose

   The G02 command is used to move the tool along a clockwise arc path.

2. Step 2: Compare with other movement commands

   G01 moves in a straight line, G03 moves counterclockwise, so G02 must be clockwise arc.

3. Final Answer:

   Moves the tool in a clockwise arc to a specified point -> Option D

4. Quick Check:

   G02 = Clockwise arc movement [OK]

Hint: G02 always means clockwise arc movement [OK]

Common Mistakes:

• Confusing G02 with G03 (counterclockwise arc)
• Thinking G02 moves in a straight line
• Assuming G02 stops the tool

2. Which of the following is the correct syntax to program a clockwise arc using G02 with I and J in CNC?

easy

A. G02 X10 Y10 I5 J0

B. G02 X10 Y10 R5

C. G02 X10 Y10 K5 L0

D. G02 X10 Y10 P5 Q0

Solution

1. Step 1: Recall the parameters for G02 arcs

   G02 uses I and J to specify the arc center relative to the start point.

2. Step 2: Identify correct parameter usage

   Only G02 X10 Y10 I5 J0 uses I and J correctly; others use invalid parameters.

3. Final Answer:

   G02 X10 Y10 I5 J0 -> Option A

4. Quick Check:

   Use I and J for arc centers with G02 [OK]

Hint: Use I and J for arc centers in G02 commands [OK]

Common Mistakes:

• Using R instead of I and J for arc center
• Using wrong letters like K, L, P, Q
• Omitting I and J parameters

3. Given the CNC code:

G00 X0 Y0
G02 X10 Y0 I5 J0

What path does the tool follow?

medium

A. A straight line from (0,0) to (10,0)

B. A clockwise arc from (0,0) to (10,0) with center at (5,0)

C. A counterclockwise arc from (0,0) to (10,0) with center at (5,0)

D. A clockwise arc from (0,0) to (10,0) with center at (0,5)

Solution

1. Step 1: Analyze start and end points

   The tool starts at (0,0) and moves to (10,0).

2. Step 2: Determine arc center from I and J

   I=5 means center is 5 units right of start (0+5=5), J=0 means no vertical offset, so center is at (5,0).

3. Step 3: Confirm arc direction

   G02 means clockwise arc, so the tool moves clockwise around center (5,0) from (0,0) to (10,0).

4. Final Answer:

   A clockwise arc from (0,0) to (10,0) with center at (5,0) -> Option B

5. Quick Check:

   G02 + I5 J0 = clockwise arc center at (5,0) [OK]

Hint: I and J are offsets from start point to arc center [OK]

Common Mistakes:

• Confusing clockwise with counterclockwise arc
• Misreading I and J as absolute coordinates
• Assuming straight line movement

4. Identify the error in this CNC code snippet:

G00 X0 Y0
G02 X10 Y10 I5 K5

medium

A. Missing G01 command before G02

B. X and Y coordinates are invalid

C. Incorrect use of parameter K instead of J for arc center

D. G02 cannot be used after G00

Solution

1. Step 1: Check parameters for arc center

   G02 requires I and J to define arc center offsets, but code uses I and K.

2. Step 2: Validate parameter correctness

   K is not a valid parameter for arc center; it should be J for Y offset.

3. Final Answer:

   Incorrect use of parameter K instead of J for arc center -> Option C

4. Quick Check:

   Use I and J for arc centers, not K [OK]

Hint: Arc center parameters are always I and J, never K [OK]

Common Mistakes:

• Using wrong letters like K or L for arc center
• Assuming G02 needs G01 before it
• Thinking G02 can't follow G00

5. You want to program a clockwise arc from (0,0) to (0,10) with a center at (5,5). Which G02 command is correct?

hard

A. G02 X0 Y10 I5 J5

B. G02 X0 Y10 I-5 J5

C. G02 X0 Y10 I-5 J-5

D. G02 X0 Y10 I5 J-5

Solution

1. Step 1: Calculate I and J relative to start point

   Start is (0,0), center is (5,5). I = center_x - start_x = 5 - 0 = 5, J = center_y - start_y = 5 - 0 = 5.

2. Step 2: Verify direction and parameters

   G02 specifies clockwise. Positive I5 J5 locate center at (5,5). The CNC interpolates clockwise arc to (0,10).

3. Step 3: Choose the option with correct parameters

   Only G02 X0 Y10 I5 J5 matches; others place center elsewhere or create radius mismatch.

4. Final Answer:

   G02 X0 Y10 I5 J5 -> Option A

5. Quick Check:

   I = cx - sx, J = cy - sy [OK]

Hint: Calculate I,J as center minus start; sign sets center position [OK]

Common Mistakes:

• Using negative I/J for positive-offset center
• Confusing center position signs
• Ignoring relative position of center to start