Depth of cut and step-over in CNC Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the depth of cut to 2 mm.

CNC Programming

depth_of_cut = [1]  # in millimeters

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

A2

B0.5

C5

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a value too large or too small for typical depth of cut.

Confusing depth of cut with step-over.

The depth of cut is set to 2 mm by assigning the value 2 to the variable depth_of_cut.

2fill in blank

medium

Complete the code to set the step-over to 40% of the tool diameter.

CNC Programming

step_over = tool_diameter * [1]  # step-over as fraction

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

A0.5

B0.4

C0.25

D0.75

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0.4 as 4 instead of 0.4.

Confusing step-over with depth of cut.

Step-over is set to 40% of the tool diameter by multiplying tool_diameter by 0.4.

3fill in blank

hard

Fix the error in the code to calculate the number of passes needed for a given total depth and depth of cut.

CNC Programming

passes = int(total_depth / [1] + 0.999)  # round up to next whole pass

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

Adepth_of_cut

Bfeed_rate

Ctool_diameter

Dstep_over

Attempts:

3 left

💡 Hint

Common Mistakes

Using step-over instead of depth of cut in the division.

Using feed rate or tool diameter incorrectly.

The number of passes depends on dividing the total depth by the depth of cut, not step-over or other values.

4fill in blank

hard

Fill both blanks to create a dictionary showing passes and step-over in mm for a tool diameter of 10 mm and depth of cut 2 mm.

CNC Programming

settings = {'passes': int(total_depth / [1] + 0.999), 'step_over_mm': [2] * tool_diameter}

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

Adepth_of_cut

B0.4

C0.5

Dstep_over

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up step-over and depth of cut in calculations.

Using 0.5 instead of 0.4 for step-over.

The number of passes is calculated using depth_of_cut. Step-over in mm is 40% (0.4) times the tool diameter.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps tool names to their step-over in mm, only if step-over is less than 5 mm.

CNC Programming

step_overs = {name: diameter * [1] for name, diameter in tools.items() if diameter * [2] [3] 5}

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

A0.4

C<

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using different fractions for calculation and condition.

Using > instead of < in the condition.

The step-over fraction is 0.4. The condition filters tools where step-over is less than 5 mm, so the operator is <.

Practice

1. What does the depth of cut control in CNC machining?

easy

A. How fast the tool moves along the path

B. How deep the tool cuts into the material each pass

C. The speed of the spindle rotation

D. The temperature of the cutting tool

Solution

1. Step 1: Understand depth of cut meaning

   Depth of cut means how far down the tool goes into the material per pass.

2. Step 2: Match with options

   How deep the tool cuts into the material each pass matches this definition exactly, others describe different parameters.

3. Final Answer:

   How deep the tool cuts into the material each pass -> Option B

4. Quick Check:

   Depth of cut = tool depth per pass [OK]

Hint: Depth of cut = vertical cut depth per pass [OK]

Common Mistakes:

• Confusing depth of cut with feed rate
• Mixing depth of cut with spindle speed
• Thinking depth of cut controls sideways movement

2. Which of the following is the correct way to specify a step-over of 0.5 mm in a CNC program line?

easy

A. STEP_OVER 0.5

B. STEP_OVER = 0.5

C. STEP_OVER(0.5)

D. STEP_OVER:0.5

Solution

1. Step 1: Identify common CNC parameter syntax

   CNC programs often use keyword followed by value without symbols for parameters.

2. Step 2: Compare options

   STEP_OVER 0.5 uses keyword and value separated by space, which is standard. Others use symbols not typical in CNC code.

3. Final Answer:

   STEP_OVER 0.5 -> Option A

4. Quick Check:

   Parameter syntax = keyword + space + value [OK]

Hint: Parameters usually use space, not symbols, between name and value [OK]

Common Mistakes:

• Adding equals sign or parentheses incorrectly
• Using colon instead of space
• Confusing step-over syntax with programming languages

3. Given a CNC program snippet:

DEPTH_OF_CUT 2.0
STEP_OVER 1.0
MILLING_PASS

What will be the depth and sideways move per pass?

medium

A. Depth 1.0 mm, Step-over 2.0 mm

B. Depth 1.0 mm, Step-over 1.0 mm

C. Depth 2.0 mm, Step-over 2.0 mm

D. Depth 2.0 mm, Step-over 1.0 mm

Solution

1. Step 1: Read parameter values

   DEPTH_OF_CUT is set to 2.0 mm, STEP_OVER is set to 1.0 mm.

2. Step 2: Match values to depth and step-over

   Depth of cut = 2.0 mm, step-over = 1.0 mm as per the program lines.

3. Final Answer:

   Depth 2.0 mm, Step-over 1.0 mm -> Option D

4. Quick Check:

   DEPTH_OF_CUT=2.0, STEP_OVER=1.0 [OK]

Hint: Match parameter names to values directly [OK]

Common Mistakes:

• Swapping depth and step-over values
• Ignoring parameter names and guessing
• Assuming default values instead of given

4. A CNC program uses DEPTH_OF_CUT 3.0 and STEP_OVER 1.5 but the tool only cuts 1.5 mm deep per pass. What is the likely error?

medium

A. The machine overrides depth to 1.5 mm for safety

B. The step-over value is too large and limits depth

C. The depth of cut parameter is ignored due to syntax error

D. The tool diameter is smaller than depth of cut

Solution

1. Step 1: Analyze parameter effect

   If depth of cut is set to 3.0 but actual cut is 1.5, likely the program did not apply 3.0 correctly.

2. Step 2: Consider syntax errors

   A syntax error in the depth of cut line can cause the machine to ignore it and use default or previous value (1.5).

3. Final Answer:

   The depth of cut parameter is ignored due to syntax error -> Option C

4. Quick Check:

   Syntax error causes parameter ignore [OK]

Hint: Check syntax if parameters don't apply as expected [OK]

Common Mistakes:

• Blaming step-over for depth issues
• Assuming machine overrides without checking code
• Ignoring syntax errors in program

5. You want to machine a 10 mm deep pocket with a tool that can safely cut 2 mm depth per pass and 40% step-over of its 5 mm diameter. How many passes and what step-over distance should you program?

hard

A. 5 passes, 2 mm step-over

B. 2 passes, 2 mm step-over

C. 5 passes, 2.5 mm step-over

D. 5 passes, 0.4 mm step-over

Solution

1. Step 1: Calculate number of passes

   Depth per pass = 2 mm, total depth = 10 mm, so passes = 10 / 2 = 5 passes.

2. Step 2: Calculate step-over distance

   Step-over = 40% of 5 mm diameter = 0.4 * 5 = 2 mm.

3. Final Answer:

   5 passes, 2 mm step-over -> Option A

4. Quick Check:

   Passes = 10/2=5, Step-over = 0.4*5=2 mm [OK]

Hint: Divide depth by cut depth; multiply diameter by step-over % [OK]

Common Mistakes:

• Confusing step-over percentage with depth
• Calculating passes incorrectly
• Using wrong tool diameter for step-over