G-Codes and M-Codes of CNC Milling Machine

Preparatory and Miscellaneous Codes

Preparatory and miscellaneous function code of milling m/c is of most importance for programming purpose. A CNC milling operator must know the various preparatory function codes of CNC milling with the advancement of electronic digital system. Computer software development made CNC milling on great demand in production engineering. Preparatory function includes address, code, block, line and miscellaneous function codes includes control panel, MDI, manuals command, floating zero, feed hold, cycle start and single block and emergency stop.

List of G Codes

All the general comments about the G codes of CNC lathes/turning centres are valid for the G codes of CNC millers/machining centres also. The following list is only a representative list which contains codes available on most of the common milling machines. Sophisticated machines use some extra codes also for which respective machine manuals should be consulted. Codes such as G04 and G28 are non-modal and are effective only in the blocks where they are called.

Code	Description
GOO	Rapid traverse
G01	Linear interpolation
G02	Circular interpolation CW
G03	Circular interpolation CCW
G04	Dwell
G17	XY plane selection
G18	ZX plane selection
G19	YZ plane selection
G20	Inch data input
G21	mm data input
G28	Reference point return
G40	Cutter radius compensation cancel
G41	Cutter radius compensation left
G42	Cutter radius compensation right
G43	Tool length compensation +ve direction
G44	Tool length compensation -ve direction
G49	Tool length compensation cancel
G73	High speed peck drilling cycle
G74	Left hand tapping cycle
G76	Fine boring cycle
G80	Canned cycle cancel
G82	Continuous drilling cycle with dwell
G83	Peck drilling cycle
G84	Right hand tapping cycle
G85	Boring cycle with feed retraction
G86	Boring cycle with rapid retraction
G87	Back boring cycle
G89	Boring cycle with dwell and feed retral
G90	Absolute movement
G91	Incremental movement
G92	Set datum
G94	Feed per minute
G95	Feed per revolution
G98	Return to initial point in a canned cycle
G99	Return to R point in a canned cycle

List of M Codes

Most of these codes are different from the codes for lathes/turning centres. So, care must be exercised while writing program for different machines.

Code	Description
MOO	Program stop
MO2	End of program
MO3	Spindle forward (CW, as viewed from the top)
MO4	Spindle reverse (CCW, as viewed from the top)
MO5	Spindle stop
MO6	Auto tool change MO8 Coolant on
MO9	Coolant off
M10	Vice open
M11	Vice close
M13	Spindle forward and coolant ON
M14	Spindle reverse and coolant ON
M19	Spindle orientate
M20	ATC IN
M21	ATC back
M22	ATC down .
M23	ATC up
M24	ATC drawbar unclamp
M25	ATC drawbar clamp
M27	Reset carousel
M30	Program reset and rewind
M32	Carousel CCW (as viewed from the top)
M33	Carousel CW (as viewed from the top)
M38	Door open.
M39	Door close
M62	Auxiliary output-1ON
M63	Auxiliary output-2 ON
M64	Auxiliary output-l OFF
M65	Auxiliary output-2 OFF
M66	Wait for input-l
M67	Wait for input-2
M70	X-mirror on M71 Y-mirror on
M76	Wait for input-l to go low
M77	Wait for input-2 to go low
M80	X-mirror OFF
M8l	Y -mirror OFF
M98	Subprogram call
M99	Subprogram exit