Understanding G-Code and M-Code in CNC Programming

IPWITHEASE | Blog,Programming & Software

Computer Numerical Control machines are operated by computers that use pre-programmed sequences of commands to control the movements of the machinery. CNC equipment includes a wide array of machinery, including lathes, grinders, and turning mills.

Without G-Code or M-Code, CNC machines cannot function. Let us take a closer look at what G and M Code are in CNC programming.

Understanding G-Code & M-Code in CNC Programming

A Brief Overview of Programming CNC Machines

All parts can be produced from a wide variety of materials by using CNC machines.


The first step is designing the part to be made using computer-aided design and computer-aided manufacturing software. Then, the instructions are turned into G and M code, enabling the machine to understand what tasks it needs to perform.

Without the need for manual operation, CNC machines speed up manufacturing capabilities and ensure consistent and accurate parts are always produced.


What is G-Code?

The main CNC programming language that is used is G code. Basically, G code tells a CNC machine where to begin, how to move, and when to stop. It enables a CNC machine to perform its operations precisely, consistently, and accurately.

However, be aware that different CNC machines read G codes in different formats. So, if you are intending to learn G code, it can be useful to know what machinery you will be programming before you start learning.

By getting in touch with a specialized provider of CNC machinery, you can find out more about which machines require which type of G code formats. You can check Revelation Machinery’s catalog of second-hand CNC machinery to start your journey.

The difference in G code formats usually comes down to the absence or presence of spaces between the commands and in the number of zeros between the number and letter commands. For instance, one machine could use the command G03 while another could use G3.

G is the most common letter used in G-code programming for CNC machines, hence the name “G-code,” but other letters are also used. Common letters used in G-code programming include:

  • A, which directs the tool around the x-axis.
  • I and J, which determine the incremental center of an arc that the tool makes.
  • N, which gives the line number.
  • R, which gives the radius of the arcs that the machine makes.
  • X, Y, and Z, which indicate the position of the tool in three dimensions, with X and Y representing the horizontal and vertical dimensions and Z representing the depth.


What is M-Code?

Basically, M code is a set of auxiliary commands that control the non-geometric actions of a CNC machine. For instance, M code controls things like stopping programs, shutting off machines after the temperature drops, and flooding machines with coolants.

M code is mostly used for turning CNC machinery on and off, so M-code should only have one command for each block of information.

Although much less common, like G codes, M code formats can vary from one CNC machine to another. Some machines do not allow the omission of the zero between the letter and the number, while others do.


The Key Differences Between G and M-Codes

Let us recap. There are three key ways in which G and M code differ from one another. They are:

  1. G code directs the motion and function of CNC machines while M-code directs the operations that do not involve movements.
  2. G code activates CNC machines while M code activates the machines’ programmable logic controller.
  3. G code commands typically differ in most CNC machines while most M code commands are the same.


Summing Up

Computer numerical control machines have revolutionized the manufacturing industry. They have made it much easier and quicker to make highly precise and consistent parts.

But without G  and M-Code, the machines would not know what to do.

Basically, G-Code instructions tell a machine exactly how to perform its operations while M-code handles the non-geometric actions of a machine.

Both G and M-code are required for CNC machinery to function properly, although the format of both codes can alter depending on the specific type of CNC machine being used.

If you are considering learning G and M-code, you can find numerous in-person and online courses to choose from.

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