Contour milling with line segments in CNC Programming - Step-by-Step Execution

Concept Flow - Contour milling with line segments

Start at first point

↓

Move to next point

↓

Mill line segment

↓

More points?

Yes→Repeat move and mill

No↓

End contour milling

The CNC machine starts at the first point, moves along each line segment milling the contour, and stops when all points are processed.

Execution Sample

CNC Programming

N10 G00 X0 Y0
N20 G01 X10 Y0 F100
N30 G01 X10 Y10
N40 G01 X0 Y10
N50 G01 X0 Y0
N60 M30

This CNC program mills a rectangular contour by moving along four line segments connecting the points.

Execution Table

Step	Command	Position (X,Y)	Feed Rate	Action	Output
1	N10 G00 X0 Y0	(0,0)	Rapid	Move to start point	At start point (0,0)
2	N20 G01 X10 Y0 F100	(10,0)	100	Mill line segment	Milled from (0,0) to (10,0)
3	N30 G01 X10 Y10	(10,10)	100	Mill line segment	Milled from (10,0) to (10,10)
4	N40 G01 X0 Y10	(0,10)	100	Mill line segment	Milled from (10,10) to (0,10)
5	N50 G01 X0 Y0	(0,0)	100	Mill line segment	Milled from (0,10) to (0,0)
6	N60 M30	(0,0)	Stop	Program end	Contour milling complete

💡 Program ends after completing all line segments of the contour.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	After Step 5	Final
Position	(0,0)	(10,0)	(10,10)	(0,10)	(0,0)	(0,0)
Feed Rate	Rapid	100	100	100	100	Stop
Action	Idle	Milling	Milling	Milling	Milling	Stopped

Key Moments - 3 Insights

Why does the machine use G00 for the first move and G01 for the others?

G00 is a rapid move to position the tool quickly without cutting (see Step 1). G01 is a controlled feed move used for milling along line segments (Steps 2-5).

How does the feed rate affect the milling process?

Feed rate controls the speed of cutting. In Steps 2-5, feed rate is set to 100 for controlled milling. Without it, the machine might move too fast or too slow.

What happens if the last line segment is not closed back to the start point?

The contour would be open, milling only partial shape. Here, Step 5 moves back to (0,0) to close the contour fully.

Visual Quiz - 3 Questions

Look at the execution table, what is the position after Step 3?

A (0,10)

B (10,0)

C (10,10)

D (0,0)

💡 Hint

Check the 'Position (X,Y)' column in row for Step 3.

At which step does the machine start milling the first line segment?

A Step 1

B Step 2

C Step 3

D Step 6

💡 Hint

Look for the first G01 command and milling action in the execution table.

If the feed rate was not set in Step 2, what would change in the execution?

A The machine would use the last feed rate set or default

B The machine would stop

C The machine would mill faster than intended

D The machine would move rapidly without cutting

💡 Hint

Refer to the 'Feed Rate' column and how CNC machines remember feed rates between commands.

Concept Snapshot

Contour milling moves the tool along connected line segments.
Use G00 for rapid positioning to start point.
Use G01 with feed rate to mill each line segment.
Close the contour by returning to start point.
Feed rate controls cutting speed.
Program ends with M30.

Full Transcript

Contour milling with line segments means moving the CNC tool along straight connected lines to cut a shape. The program starts by moving rapidly to the first point using G00. Then it uses G01 commands with a feed rate to mill each line segment in order. The tool moves from point to point, cutting the contour. The feed rate controls how fast the tool cuts. The program closes the shape by returning to the start point. Finally, the program ends with M30. This step-by-step process ensures the contour is milled accurately and efficiently.