Work coordinate system (WCS) in CNC Programming - Step-by-Step Execution

Concept Flow - Work coordinate system (WCS)

Machine Home Position

↓

Set WCS Origin

↓

Program uses WCS

↓

Tool moves relative to WCS

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Workpiece Machined Correctly

The machine starts at a fixed home position, then the operator sets the WCS origin on the workpiece. The CNC program uses this WCS to move the tool relative to the workpiece for accurate machining.

Execution Sample

CNC Programming

G54
G0 X0 Y0 Z0
G1 X50 Y25 Z-5 F100

This CNC code sets the WCS to G54, moves the tool to the WCS origin, then cuts a line to X=50, Y=25, Z=-5 at feed rate 100.

Execution Table

Step	Command	Action	Coordinates (X,Y,Z)	Feed Rate	Result
1	G54	Set WCS origin	N/A	N/A	WCS origin set to machine coordinates at current position
2	G0 X0 Y0 Z0	Rapid move to WCS origin	(0,0,0)	Rapid	Tool positioned at WCS origin
3	G1 X50 Y25 Z-5 F100	Linear cut move	(50,25,-5)	100	Tool moves cutting along specified path
4	End of program	No more commands	N/A	N/A	Program ends, machining complete

💡 Program ends after cutting to specified coordinates relative to WCS

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
WCS Origin	Machine Home	Set to current position	Set to current position	Set to current position	Set to current position
Tool Position	(X?,Y?,Z?)	(X?,Y?,Z?)	(0,0,0)	(50,25,-5)	(50,25,-5)
Feed Rate	N/A	N/A	Rapid	100	100

Key Moments - 3 Insights

Why does the tool move to (0,0,0) after setting G54?

Because G54 sets the WCS origin, so coordinates (0,0,0) refer to that origin, not machine home. See execution_table step 2.

What does the coordinate (50,25,-5) mean in the program?

It means the tool moves 50 units in X, 25 in Y, and -5 in Z relative to the WCS origin set by G54. See execution_table step 3.

Why is feed rate 'Rapid' at step 2 and '100' at step 3?

Because G0 commands rapid moves (fast, no cutting), and G1 commands linear cutting moves at specified feed rate. See execution_table steps 2 and 3.

Visual Quiz - 3 Questions

Look at the execution table, what are the tool coordinates after step 2?

A (0,0,0)

B (50,25,-5)

C (Machine Home)

D (Undefined)

💡 Hint

Check the 'Coordinates' column in execution_table row for step 2

At which step does the tool start cutting the workpiece?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look for the step with G1 command and feed rate 100 in execution_table

If we change G54 to G55, what changes in the execution?

A Tool position stays the same

B WCS origin changes to G55 coordinates

C Feed rate changes to 200

D Program ends immediately

💡 Hint

G54 and G55 are different WCS origins, see execution_table step 1 explanation

Concept Snapshot

Work Coordinate System (WCS):
- Defines origin on workpiece for CNC moves
- G54 to G59 select different WCS
- Coordinates in program are relative to WCS
- G0 = rapid move, G1 = linear cut move
- Setting WCS ensures accurate machining position

Full Transcript

The Work Coordinate System (WCS) is a reference point set on the workpiece to guide CNC tool movements. The machine starts at a fixed home position. The operator sets the WCS origin using commands like G54. After setting WCS, coordinates in the CNC program are relative to this origin. For example, moving to X0 Y0 Z0 moves the tool to the WCS origin. Then, commands like G1 X50 Y25 Z-5 move the tool relative to that origin to cut the workpiece. Rapid moves (G0) move the tool quickly without cutting. This system helps ensure the tool machines the part accurately based on the workpiece location, not just the machine's home position.