G-Code is the common name for the programming language of CNC Machines. Somewhat of a generic, catch-all type of term for CNC programming language. Very few machines adhere to this standard today. There are as many variations as there are manufacturers.

This is how I think of G-Code. It is a simple language built off of the Cartesian Coordinate System for motion control. That is a mouthful. I don't know if that is exactly right, but you will get my meaning in a second when we go through some code line by line. You will remember your High School Geometry soon enough. For the real pros out there, you know there is much more to G-Code then that, but it is a good place to start thinking about it.

You will see many variations of the G-Code name like:

Gcode

gcode

G-Code

g-code

G Code

G-Code

Are there other "Codes?"

In a word, Yes. We will get to that in a moment. G-code is also the name of any command in a CNC program that begins with the letter G. G-Codes generally tell the machine to perform an action. G-Codes can tell machines to move a certain distance in the X-Axis for example. Or, make a rapid move to another location. Or, move in an arcing fashion while milling. An on and on and on.

Here are some examples of G-Codes

Remember these codes change to a certain degree between CAM Software packages and CNC Machine Manufacturers.

G00 Rapid positioning

G01 Linear interpolation

G02 CW circular interpolation

G03 CCW circular interpolation

G04 Dwell

G20 Programming in inches

G21 Programming in mm

G28 Return to home position

G40 Tool radius compensation off

G41 Tool radius compensation left

G42 Tool radius compensation right

G43 Tool offset compensation positive

G44 Tool offset compensation negative

Why does G-Code Change?

We humans like flexibility. We also like standards. G-Codes are standardized in a certain sense. Once you start to be able to read it, you can read just about any flavor of it. That is the standardized part.

All machines are not created alike. Even identical machines are different to a certain degree. They may not have the same tools loaded or they have been slightly modified to produce a certain type of part. Interesting how people like to customize.

That is why G-Codes are not the same. You need some flexibility in the programming to accommodate all situations. Couple that with the fact that every manufacturer thinks their version is the best and you get a myriad of G-Codes out there.

Many manufacturers also try to force you to only use their code. For example, they give you a design interface to make parts and a CAM interface to produce code. They lock you into their "Black Box" so you can't go elsewhere for service and support. They lock you in their "Family." Sometimes they make up a completely different kind of G-Code language that no one can understand but them. They do that to keep your hands tied up.

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