Pocket milling (rectangular) in CNC Programming - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Output of a simple rectangular pocket milling G-code

What is the final position of the tool after executing this G-code snippet for a rectangular pocket milling?

G90 G00 X0 Y0 Z5
G01 Z-2 F100
G01 X50 Y0 F200
G01 X50 Y30
G01 X0 Y30
G01 X0 Y0
G00 Z5

CNC Programming

G90 G00 X0 Y0 Z5
G01 Z-2 F100
G01 X50 Y0 F200
G01 X50 Y30
G01 X0 Y30
G01 X0 Y0
G00 Z5

A X50 Y30 Z-2

B X0 Y0 Z-2

C X0 Y0 Z5

D X50 Y30 Z5

💡 Hint

Look at the last move command and the Z height it sets.

The last command is G00 Z5, which moves the tool up to Z=5 at the current XY position (which is X0 Y0). So the final position is X0 Y0 Z5.

🧠 Conceptual

intermediate

Understanding step-over in rectangular pocket milling

In rectangular pocket milling, what does the term step-over refer to?

A The distance the tool moves down in Z-axis after each pass

B The lateral distance the tool moves sideways between passes to cover the pocket area

C The speed at which the tool moves along the pocket edges

D The diameter of the cutting tool used

💡 Hint

Think about how the tool covers the entire rectangular area.

Step-over is the sideways distance the tool moves between passes to ensure the entire pocket is milled without gaps.

🔧 Debug

advanced

Identify the error in this rectangular pocket milling G-code

This G-code is intended to mill a rectangular pocket 40mm wide and 20mm deep. What error will occur when running it?

G90 G00 X0 Y0 Z5
G01 Z-20 F100
G01 X40 Y0 F200
G01 X40 Y20
G01 X0 Y20
G01 X0 Y0
G00 Z5

CNC Programming

G90 G00 X0 Y0 Z5
G01 Z-20 F100
G01 X40 Y0 F200
G01 X40 Y20
G01 X0 Y20
G01 X0 Y0
G00 Z5

A The tool will crash because Z-20 is too deep without incremental steps

B The feed rate F200 is too slow for XY moves

C The toolpath is missing a command to start spindle rotation

D No error, the code will run correctly

💡 Hint

Consider typical machining practice for depth of cut.

Cutting 20mm deep in a single pass is usually too deep and can cause tool breakage or machine crash. Depth should be taken in multiple passes.

🚀 Application

advanced

Calculate number of passes for rectangular pocket milling

You want to mill a rectangular pocket 48mm wide using a 10mm diameter tool with a 40% step-over. How many passes are needed to cover the width?

A 12 passes

B 15 passes

C 8 passes

D 10 passes

💡 Hint

Calculate step-over distance and divide pocket width by it, then round up.

Step-over distance = 10mm * 0.4 = 4mm. Number of passes = ceil(48 / 4) = 12 passes.

📝 Syntax

expert

Identify the syntax error in this rectangular pocket milling G-code snippet

Which option contains a syntax error that will cause the CNC machine to reject the program?

G90 G00 X0 Y0 Z5
G01 Z-5 F100
G01 X40 Y0 F200
G01 X40 Y20
G01 X0 Y20
G01 X0 Y0
G00 Z5

A G01 X40 Y20

B G01 Z-5 F100

C G00 Z5

D G01 X40 Y0 F

💡 Hint

Check if all commands have correct syntax and parameters.

Option D ('G01 X40 Y0 F') has F without a numerical value, which is a syntax error that will cause the CNC machine to reject the program.