Depth of cut and step-over in CNC Programming - Step-by-Step Execution

Concept Flow - Depth of cut and step-over

Start CNC Operation

↓

Set Depth of Cut

↓

Set Step-Over

↓

Begin Cutting Pass

↓

Cut to Depth

↓

Move Step-Over

↓

Check if Area Complete?

No→Repeat Cutting Pass

Yes↓

End Operation

This flow shows how CNC cutting uses depth of cut and step-over to remove material layer by layer until the area is fully machined.

Execution Sample

CNC Programming

depth_of_cut = 2.0  # mm
step_over = 1.0      # mm
material_thickness = 6.0  # mm
current_depth = 0.0

while current_depth < material_thickness:
    current_depth += depth_of_cut
    print(f"Cutting at depth {current_depth} mm")
    print(f"Moving step-over by {step_over} mm")

This code simulates cutting a material 6 mm thick by removing 2 mm depth each pass and moving 1 mm sideways after each cut.

Execution Table

Iteration	current_depth (mm)	Condition (current_depth < 6.0)	Action	Output
1	0.0 + 2.0 = 2.0	0.0 < 6.0 = True	Cut at 2.0 mm, move 1.0 mm step-over	Cutting at depth 2.0 mm Moving step-over by 1.0 mm
2	2.0 + 2.0 = 4.0	2.0 < 6.0 = True	Cut at 4.0 mm, move 1.0 mm step-over	Cutting at depth 4.0 mm Moving step-over by 1.0 mm
3	4.0 + 2.0 = 6.0	4.0 < 6.0 = True	Cut at 6.0 mm, move 1.0 mm step-over	Cutting at depth 6.0 mm Moving step-over by 1.0 mm
4	6.0	6.0 < 6.0 = False	Stop cutting

💡 At iteration 4, current_depth 6.0 is not less than material_thickness 6.0, so loop stops.

Variable Tracker

Variable	Start	After 1	After 2	After 3	After 4 (exit)
current_depth	0.0	2.0	4.0	6.0	6.0
depth_of_cut	2.0	2.0	2.0	2.0	2.0
step_over	1.0	1.0	1.0	1.0	1.0

Key Moments - 2 Insights

Why does the loop stop without current_depth exceeding material thickness?

The loop condition checks if current_depth is less than material_thickness before adding depth_of_cut. At iteration 4, current_depth is 6.0 which is equal to material_thickness, so the loop stops before adding 2.0 again (see execution_table row 4).

What is the difference between depth of cut and step-over?

Depth of cut is how deep the tool cuts into the material vertically each pass. Step-over is how far the tool moves sideways horizontally after each cut to cover the whole area (see execution_table outputs).

Visual Quiz - 3 Questions

Look at the execution table, what is the value of current_depth after iteration 2?

A 4.0 mm

B 2.0 mm

C 6.0 mm

D 8.0 mm

💡 Hint

Check the 'current_depth (mm)' column for iteration 2 in the execution_table.

At which iteration does the loop condition become false and stop the cutting?

A Iteration 3

B Iteration 2

C Iteration 4

D Iteration 5

💡 Hint

Look at the 'Condition' column in the execution_table where it becomes False.

If the depth_of_cut was changed to 3.0 mm, how many cutting passes would be needed to reach 6.0 mm thickness?

A 3 passes

B 2 passes

C 1 pass

D 4 passes

💡 Hint

Think about how many times 3.0 mm fits into 6.0 mm, referencing the variable_tracker for current_depth changes.

Concept Snapshot

Depth of cut is how deep the tool cuts vertically each pass.
Step-over is how far the tool moves sideways after each cut.
Cutting repeats until total depth reaches material thickness.
Adjust depth and step-over to balance speed and finish quality.
Loop stops when depth reaches or exceeds material thickness.

Full Transcript

This lesson shows how CNC machines cut material layer by layer using two key settings: depth of cut and step-over. Depth of cut controls how deep the tool cuts into the material each pass, while step-over controls how far the tool moves sideways to cover the area. The example code simulates cutting a 6 mm thick material by removing 2 mm depth each pass and moving 1 mm sideways after each cut. The execution table traces each pass, showing current depth increasing by 2 mm until it reaches 6 mm, then stopping. The variable tracker shows how current_depth changes after each iteration. Key moments clarify why the loop stops exactly at the material thickness and the difference between depth of cut and step-over. The quiz tests understanding of these values and loop behavior. This visual step-by-step helps beginners see how CNC cutting progresses in layers and moves sideways to finish the job.