Program end (M30) in CNC Programming - Step-by-Step Execution

Concept Flow - Program end (M30)

Start CNC Program

↓

Execute machining commands

↓

Reach M30 command

↓

Stop spindle and coolant

↓

Reset program to start

↓

Program ready for next cycle

The CNC program runs commands until it reaches M30, which stops the machine and resets the program to the start.

Execution Sample

CNC Programming

N10 G01 X10 Y10 F100
N20 G01 X20 Y20
N30 M30

This CNC program moves the tool to two positions and then ends the program with M30.

Execution Table

Step	Command	Action	Machine State	Output
1	N10 G01 X10 Y10 F100	Move tool to X10 Y10 at feed 100	Tool moving to X10 Y10	Position updated to X10 Y10
2	N20 G01 X20 Y20	Move tool to X20 Y20	Tool moving to X20 Y20	Position updated to X20 Y20
3	N30 M30	Stop spindle and coolant, reset program	Machine stopped, program reset	Program ended and ready to restart

💡 M30 command stops the machine and resets the program to the start.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3
Position	X0 Y0	X10 Y10	X20 Y20	X20 Y20
Spindle	On	On	On	Off
Program Counter	N10	N20	N30	Reset to N10

Key Moments - 2 Insights

Why does the program reset to the start after M30?

Because M30 is designed to stop the machine and reset the program counter to the beginning, as shown in step 3 of the execution_table.

Does the tool move after M30 command?

No, after M30 the machine stops all motion and spindle, so the tool stays at the last position (X20 Y20) as seen in variable_tracker.

Visual Quiz - 3 Questions

Look at the execution_table, what is the machine state after step 2?

A Program reset

B Machine stopped

C Tool moving to X20 Y20

D Tool moving to X10 Y10

💡 Hint

Check the 'Machine State' column in row 2 of execution_table.

At which step does the spindle turn off?

A Step 2

B Step 3

C Step 1

D Never

💡 Hint

Look at the 'Spindle' variable in variable_tracker after each step.

If M30 was removed, what would happen to the program counter after step 3?

A It would stay at N30

B It would reset to N10

C It would move to next line after N30

D It would cause an error

💡 Hint

M30 resets the program counter; without it, the counter stays at the last command.

Concept Snapshot

M30 command ends a CNC program.
It stops spindle and coolant.
Resets program to start.
Prepares machine for next run.
Used at program end.

Full Transcript

This CNC program example shows moving the tool to two positions with G01 commands, then ending with M30. The M30 command stops the spindle and coolant, then resets the program counter to the start, ready for the next cycle. The execution table traces each step, showing tool moves and machine state changes. The variable tracker follows position, spindle state, and program counter. Key moments clarify why M30 resets the program and stops motion. The quiz tests understanding of machine state and program flow at each step.