Articles on: About 3D printers

What is Gcode for 3D printing, and how to read and write it

In this article, you'll learn about Gcode and its crucial role in 3D printing and CNC operations!

TLDR; Gcode, or G-Code, is the language used by 3D printers and CNC machines to create complex, detailed objects. It translates 3D models into instructions your 3D printer understands. For 3D printing, Gcode tells the printer where to move, how fast to move, and what to do. In CNC operations, Gcode directs the machine where to drill, cut, shape, or carve.

What is it?


Gcode (short for 'Geometric Code') is a language that 3D printers and CNC machines use to know what actions to perform and in which order. For 3D printing, the Gcode contains instructions about how the printer should move the print head, and how much filament it should extrude. It translates the information from your 3D model file into a list of coordinates and commands for the printer to follow.

This code allows the printer to create a physical object layer by layer, starting from the bottom. The Gcode guides the movement of the printer's nozzle (or other tools) along the X, Y, and Z axes to create the object's shape, taking into account factors such as the print speed, layer height, and other printer-specific settings.

Just as an orchestra follows a conductor's baton, your 3D printer follows Gcode instructions to "perform" your 3D prints!

Firmware and Gcode: Marlin and Klipper


Firmware is the software "embedded" within your 3D printer that translates Gcode into electrical signals to control the printer's motors, heaters, and other components. Two of the most popular firmware choices in the 3D printing community are Marlin and Klipper.

Marlin is open-source firmware primarily designed for RepRap project-based FDM (Fused Deposition Modelling) printers. It's known for its reliability and comprehensive feature set, and it interprets Gcode to control the printer.

Klipper, on the other hand, takes a different approach. Instead of running the full firmware on the microcontroller alone, it splits the task with a Linux system (like a Raspberry Pi). Klipper firmware interprets Gcode and translates it into simpler, real-time commands that the microcontroller can understand, enabling more precise control and faster speeds.

In both firmware options, Gcode plays the pivotal role of guiding your 3D printer's actions.

Common Gcodes



Check out the Marlin Gcode documentation for info on all the available Gcode commands! https://marlinfw.org/meta/gcode/

While Gcode consists of many commands, some are more commonly used than others in 3D printing. Here are a few examples:

- G1: This command is used for linear moves. In a 3D printing context, it typically tells the print head to move to a specific position. For example, 'G1 X50 Y50' instructs the printer to move the head to the point located at 50mm on the X-axis and 50mm on the Y-axis.

- M104: This sets the extruder temperature to a certain value. For instance, 'M104 S200' will set the extruder temperature to 200°C. Importantly, this command doesn't wait for the temperature to reach the target before moving to the next instruction.

- M109: Similar to M104, this command also sets the extruder temperature, but it pauses the printer until the target temperature is reached. For example, 'M109 S200' sets the extruder temperature to 200°C and waits until the extruder has heated up to that temperature before proceeding.

Remember that different printers and firmware might use slightly different Gcodes, so it's always essential to refer to your specific printer's manual or the firmware's documentation for exact codes and their functions.


Bonus info: Gcode in CNC Operations


While this article primarily focuses on 3D printing, it's worth noting that Gcode is also essential in CNC (Computer Numerical Control) machining. In CNC, Gcode is used to control automated machine tools like drills, lathes, mills, and more. It helps these machines produce parts with high precision in industries such as manufacturing, aerospace, automotive, and more.

So whether you're printing a miniature model or carving a complex piece of machinery, Gcode is the universal language that brings your digital designs to life!

Updated on: 22/05/2023

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