Short Note on G and M codes in CNC machine.

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written 9.4 years ago by

teamques10 ★ 70k

A CNC part programming begins with a %MPF file which signifies the beginning of a program. A part program is a series of coded instructions required to produce a part. It controls the movement of the machine tool and the on/off control of auxiliary functions such as spindle rotation and coolant. The coded instructions are composed of letters, numbers and symbols and are arranged in a format of functional blocks representing an operation to be carried out in the machining of a part.

G Codes: Preparatory Functions

It involves the actual tool movement. It is followed by a two digit number e.g. G00, G90, etc. The preparatory functions instruct the machines what to do via the customer’s CNC program. Some of the common G codes are listed below.

Code	Operation	Function
G17,G18,G19	Plane Selection	This function identifies on which plane the machining is to be carried out. G17: x-y plane G18: x-z plane G19: y-z plane
G94	Feed rate	The feed rate is specified in mm/min or inch/min.
G01	Linear Interpolation	With G01 the tool travels along a straight line in which the velocity is held constant.

M codes: Miscellaneous functions

The perform a variety of auxiliary commands such as stopping the program, stopping and starting the spindle, tool changes coolant on/off etc. they are used at the beginning or the end of the cycle and are identified by the letter address “M” followed by a two digit number.

Code	Operation	Function
M00	Program stop	It cancels the spindle and coolant functions
M06	Tool change	Stops spindle and coolant and then changes the tool at the set point.
M08	Coolant “ON”	Witches on the coolant system

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