Pocket milling (rectangular) in CNC Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start the spindle clockwise.

CNC Programming

M3 [1]

Drag options to blanks, or click blank then click option'

AM5

BF200

CG1

DS1000

Attempts:

3 left

💡 Hint

Common Mistakes

Using M5 which stops the spindle.

Using G1 which is a linear move command.

Using F200 which sets feed rate, not spindle speed.

M3 starts the spindle clockwise and S1000 sets the spindle speed to 1000 RPM.

2fill in blank

medium

Complete the code to move the tool to the start point at X10 Y20.

CNC Programming

G0 [1] Y20

Drag options to blanks, or click blank then click option'

AZ-5

BX10

CF100

DM3

Attempts:

3 left

💡 Hint

Common Mistakes

Using Z-5 which moves tool down, not X axis.

Using F100 which sets feed rate, not position.

Using M3 which starts spindle, not moves tool.

G0 is a rapid move command. X10 moves the tool to X=10 coordinate.

3fill in blank

hard

Fix the error in the feed move command to cut at feed rate 150.

CNC Programming

G1 X30 Y40 F[1]

Drag options to blanks, or click blank then click option'

A150

BG0

C300

DM3

Attempts:

3 left

💡 Hint

Common Mistakes

Using 300 which is too fast for this task.

Using M3 which is spindle start command.

Using G0 which is rapid move, not feed rate.

F150 sets the feed rate to 150 units per minute during the G1 cutting move.

4fill in blank

hard

Fill both blanks to define a rectangular pocket from X10 to X50 and Y20 to Y60.

CNC Programming

G1 X[1] Y[2] F100

Drag options to blanks, or click blank then click option'

A10

B60

C20

D50

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping X and Y values.

Using values outside the pocket range.

Using feed rate instead of coordinates.

X50 and Y60 define one corner of the rectangular pocket boundary.

5fill in blank

hard

Fill all three blanks to create a dictionary of pocket corners with their coordinates.

CNC Programming

pocket = {{'start_x': [1], 'start_y': [2], 'end_x': [3]

Drag options to blanks, or click blank then click option'

A10

B20

C50

D60

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up start and end coordinates.

Using Y coordinate for end_x key.

Leaving blanks empty.

The dictionary keys map to the pocket's start and end coordinates correctly.

Practice

1. What is the main purpose of pocket milling in CNC programming?

easy

A. To drill holes in a workpiece

B. To cut the outer shape of a part

C. To remove material inside a rectangular area

D. To polish the surface of a workpiece

Solution

1. Step 1: Understand pocket milling definition

   Pocket milling is used to clear out material inside a defined area, usually rectangular.

2. Step 2: Compare with other machining operations

   Drilling makes holes, contouring cuts outer edges, polishing smooths surfaces, so they differ from pocket milling.

3. Final Answer:

   To remove material inside a rectangular area -> Option C

4. Quick Check:

   Pocket milling = remove inside rectangle [OK]

Hint: Pocket milling clears inside areas, not edges or holes [OK]

Common Mistakes:

• Confusing pocket milling with drilling
• Thinking pocket milling cuts outer edges
• Assuming pocket milling polishes surfaces

2. Which G-code command is used to move the tool quickly without cutting during pocket milling?

easy

A. G1

B. G3

C. G2

D. G0

Solution

1. Step 1: Identify G-code commands for movement

   G0 moves the tool rapidly without cutting; G1 moves with controlled feed for cutting.

2. Step 2: Differentiate G2 and G3

   G2 and G3 are used for circular interpolation, not rapid moves.

3. Final Answer:

   G0 -> Option D

4. Quick Check:

   Rapid move = G0 [OK]

Hint: G0 is rapid move; G1 is cutting move [OK]

Common Mistakes:

• Using G1 for rapid moves
• Confusing G2/G3 with rapid moves
• Mixing up G0 and G1 commands

3. Given this CNC code snippet for pocket milling, what is the tool's final position?

G0 Z5
G0 X0 Y0
G1 Z-2 F100
G1 X50 Y0 F200
G1 X50 Y30
G1 X0 Y30
G1 X0 Y0
G0 Z5

medium

A. X0 Y0 Z5

B. X0 Y0 Z-2

C. X50 Y30 Z-2

D. X50 Y30 Z5

Solution

1. Step 1: Trace the tool movements

   The tool starts at Z5 (safe height), moves to X0 Y0, then lowers to Z-2 to cut the pocket edges in sequence.

2. Step 2: Identify final move

   After completing the rectangle, the tool moves back up to Z5 (safe height) at the last position X0 Y0.

3. Final Answer:

   X0 Y0 Z5 -> Option A

4. Quick Check:

   Ends at start point with safe height Z5 [OK]

Hint: Final move is rapid up at start point [OK]

Common Mistakes:

• Ignoring the final Z5 move
• Assuming tool stays lowered after cutting
• Confusing last XY position with intermediate points

4. Identify the error in this pocket milling code snippet:

G0 Z5
G0 X0 Y0
G1 Z-2 F100
G1 X50 Y0 F200
G1 X50 Y30
G1 X0 Y30
G1 X0 Y0
G1 Z5

medium

A. Starting at Z5 instead of Z0

B. Using G1 to move up to Z5 instead of G0

C. Missing feed rate on last move

D. No error, code is correct

Solution

1. Step 1: Check movement commands for safe height

   Raising the tool to safe height (Z5) should use rapid move G0, not cutting move G1.

2. Step 2: Understand feed rate relevance

   Feed rate missing on last move is acceptable for G1 if previous feed rate applies; starting at Z5 is correct.

3. Final Answer:

   Using G1 to move up to Z5 instead of G0 -> Option B

4. Quick Check:

   Safe height moves use G0, not G1 [OK]

Hint: Use G0 for rapid moves up/down [OK]

Common Mistakes:

• Using G1 for rapid moves
• Ignoring feed rate importance
• Confusing start height with error

5. You want to program a rectangular pocket 40mm wide and 25mm tall. The tool diameter is 10mm, and you want to mill in two passes to reach a depth of 4mm. Which approach correctly plans the passes?

hard

A. Cut 2mm depth in first pass, then 2mm in second pass along same path

B. Cut full depth 4mm in one pass along the rectangle edges

C. Cut 1mm depth in first pass, then 3mm in second pass along same path

D. Cut 4mm depth in first pass, then retract and cut again at 2mm

Solution

1. Step 1: Understand depth per pass for tool safety

   Cutting full 4mm depth at once risks tool damage; splitting into equal passes is safer.

2. Step 2: Plan passes to reach total depth

   Two passes of 2mm each sum to 4mm total depth, following same rectangular path for pocket milling.

3. Final Answer:

   Cut 2mm depth in first pass, then 2mm in second pass along same path -> Option A

4. Quick Check:

   Equal depth passes sum to total depth safely [OK]

Hint: Split total depth evenly for multiple passes [OK]

Common Mistakes:

• Cutting full depth in one pass
• Unequal depth passes causing tool stress
• Retracting unnecessarily between passes