What is a G-Code and What is its Use in 3D Printing?

As we know, additive manufacturing goes far beyond simply turning on the machine and pushing a button. There are many steps behind this process, from the design of a part to its final post-processing, and all the steps in-between. One of these important steps before starting to 3D print is that it is necessary for the model in question to go through a cutting software, also called slicers. In these programs, what happens is that an STL design file is converted into a control file for the 3D printer. This file is composed of the so-called G-Code, a programming language that allows the machine to understand what commands it must follow to manufacture the final part. But what is this digital language and how important is it in the manufacturing process?

The G-Code consists of G and M commands, each with an assigned motion or action. The combination of these commands will allow the 3D printer to understand which pattern to follow in order to create the final part. As we have said, this is a language automatically generated by the cutting software when converting the design into an STL file. In this case we will focus only on FDM 3D printers, so we will refer to terms such as extruder, print tray, or thermoplastic filaments. Among the different types of commands that the 3D printer will interpret, we find commands for movement, extrusion, heating and detection in a sequence. This is the basis for understanding the importance of this language, however, let us now see the numerical composition of a G-Code to be able to read the command in question.

The G-Code language is automatically generated by the slicer (photo credits: Ultimaker Cura)

What is a G-Code made up of?

First we must understand the difference between a G-Code and an M-Code. Both are commands included in the file and tell the printer how and where to extrude the material. The only difference is that G-Codes are universally understood by printers using G-Codes, and M-Codes are those codes that are specific to individual printer lines. So, as we can see in the picture below, the language is made up of several parameters. The basic things to know when reading such a code are the different alphanumeric values.