CNC (Computer Numerical Control) is a technology used to control processing machines using a computer-controlled system. The basis of CNC is G-code and M-code. G-code controls the movement of the cutting tool, while M-code generally controls the various functions of the machine.
Some basic G and M codes that are commonly used:
G-Codes:
G00: Rapid positioning
G01: Linear motion (Linear interpolation)
G02: Clockwise circular interpolation
G03: Counterclockwise circular interpolation
G04: Wait or time delay (Dwell)
G17, G18, G19: Machining selection in XY, XZ and YZ planes (Plane selection)
G20: Working in inch mode
G21: Working in millimeter mode
G28: Return to home position
G90: Absolute coordinate mode (Absolute programming)
G91: Incremental coordinate mode (Incremental programming)
M Codes:
M00: Program stop
M01: Optional stop
M03: Spindle on, clockwise rotation
M04: Spindle on, counterclockwise rotation
M05: Spindle stop
M06: Tool change
M08: Coolant on
M09: Coolant off
M30: End of program, rewind and reset
M98: Calling a subroutine
M99: Returning from a subroutine
These codes are commonly used on CNC machining machines. However, each CNC machine can be manufacturer specific and therefore it is important to consult the user manuals.