G-code

[pukiwawa]

Guys,

I am new to CNC programming, especially G-code.
Can I know what does the G which used in G-code stands for?
Is it GO?
How about T, M? Tools? Mode?

[Geof]

The G does not really stand for anything; G codes are called preparatory functions, M vodes are called miscellaneous functions.

If you look at a list of G codes you will see they are involved with specifying the coordinates the machine should move to in absolute mode or the distance the machine should move in incremental mode. So G codes have coordinates following thim such as G00 X0. Y0. Z0. which in this case menas make a rapid move to the zero location on all three axes. Other G codes such as G54 tell the controller to use a particular reference point. To tell the machine how fast to move an F value is included when the G code for a feed move is used as in G01 X2. Y2. Z-.1 F20. which just tells the machine to move at 20 inches per minute or mm per minute depending on the measurement system being used.

M codes are generally commands to turn things on or off such as M03 start spindle forward, a speed is also needed so the complete command is M03 S10000 to start the spindle forward at 10,000 rpm. M08 on many machines means start the coolant pump, M06 means do a toolchange so a tool number is needed such as T1 M06; change to tool number one.

Do not try to find any logic behind G codes or M codes or many of the other codes like P which sometimes means seconds and other times means line number as in G04 P2000 which means pause the program for 2000 seconds and M97 P1000 which means jump to line N1000 in the program. Or sometimes P2000 means 2000 milliseconds and instead of P O is used to mean jump to a line.

Have I confused you, Sorry, G codes can be confusing if you try to make sense of them; just learn them and use them.

[pukiwawa]

I did try to ignore the meaning of G until today my boss test me on it during my interview....
I was stunned.
:-D

[g-codeguy]

Originally Posted by pukiwawa I did try to ignore the meaning of G until today my boss test me on it during my interview.... I was stunned. :-D

Probably because he hasn't the first clue about programming.

[Al_The_Man]

Also G codes can be machine specific, i.e. there are unique codes which are 'standard' for Lathe, Mill, EDM, Plasma/Gas, Punch for example.
The control manufacturer sets the G codes in its servo positioner control, the M,S,T are usually programmed by the MTB or Retro-fitter in the machine controller where they are passed over from the part program.
Al.

[Switcher]

I could be wrong (that's never happend ), but I think that Joseph Gerber of Gerber Scientific was the man behind the G in g-code.

Here is some NC history from MIT, read the second to the last paragraph.

A significant postwar project that began in 1949 and continued and evolved through the 1950s was the work that led to numerical control of machine tools. Under a contract with the Parsons Company of Michigan, William M. Pease and James O. McDonough designed an experimental numerically-controlled milling machine which received directions through data on punched paper tape. The first working model of a continuous-path numerically-controlled milling machine was demonstrated in 1952. Further research was then carried out under the sponsorship of the U.S. Air Force. Subsequently, the laboratory’s Computer Application Group, led by Douglas T. Ross, developed the Automatically Programmed Tool Language (APT), an easy-to-use, special purpose programming language. Eventually, APT became the world standard for programming computer-controlled machine tools. The Servomechanisms Laboratory staff actively promoted the introduction and use of numerical control for industrial processes. It sponsored conferences and summer sessions aimed at industry personnel. The development of numerical controls had a profound impact. The introduction of automated controls revolutionized the machine tool industry. In 1958, further development of the APT system was turned over to a coordinating group sponsored by the Aircraft Industries Association.