Understanding G-Code: A Beginner’s Guide to 3D Printing Commands

    3D PrintersUnderstanding G-Code: A Beginner's Guide to 3D Printing Commands


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    Stepping into the world of 3D printing can be exciting, yet sometimes daunting due to technical terms like G-Code. As a fundamental aspect of this innovative technology, G-Code is used to instruct and control how your 3D printer operates.

    In this blog post, we’ll go over G-Code basics for beginners from explaining what it is, its syntax, common commands in 3D printing all the way to how you can write your custom code! Ready to demystify G-Code? Keep reading!

    Key Takeaways

    • G – Code is a programming language used in 3D printing to control the movements and actions of the printer.
    • Understanding G – Code syntax and structure allows for customizing prints and optimizing print quality.
    • Common G – Code commands include G0 for rapid linear motion, G1 for controlled linear motion, G90 for absolute positioning, and G91 for relative positioning.
    • Creating custom G – Code involves understanding the structure, identifying parameters, using variables, experimenting with slicing software, testing and refining.

    What is G-Code and How Does it Work in 3D Printing?

    G-Code is a programming language used in 3D printing to control the movements and actions of the printer. It consists of specific commands that tell the printer how to move, position, and extrude filament.

    Understanding G-Code is essential for customizing prints and optimizing print quality.

    G-Code basics

    G-Code is a key part of 3D printing. It tells the printer what to do and how to move. Each line of G-Code sends a command. This could be moving the print head, heating up parts, or making layers in a design.

    The printer reads these lines one by one until it finishes the job. Using G-Code lets you have full control over your 3D prints.

    Syntax and structure

    G-Code for 3D printing has its own syntax and structure. It consists of a series of commands that tell the printer what to do. Each command starts with a letter, followed by numbers or other codes.

    For example, G0 and G1 are used for linear motion, while G90 and G91 determine absolute or relative positioning. There are also commands like G28 for auto homing and bed leveling, and M104/M109 for temperature control.

    Understanding the syntax and structure of G-Code is important because it allows you to write custom commands and modify existing ones to achieve precise control over your 3D prints.

    Common commands used in 3D printing

    G-Code consists of a series of commands that dictate the machine’s movement and actions in 3D printing. Let’s take a look at some of the most common ones:

    Command Description
    G0 Indicates rapid linear motion. This means the 3D printer moves as fast as possible from one location to another.
    G1 Signifies controlled linear motion. This is the primary command used for 3D printing, as it moves the printer head at a specified speed along a particular path.
    G90 Switches the printer to absolute positioning mode, where coordinates are given as positions from the origin point of the 3D print bed.
    G91 Changes the printer to relative positioning mode, where coordinates are given as distances from the current position of the machine.
    G28 Commands an auto homing sequence, where the printer moves all axes to their zero points.
    G29 Starts a bed leveling process. This helps ensure that the print adheres properly to the print bed by adjusting the nozzle distance from the bed at different points.
    M104 Sets the extruder temperature to a specified value and continues with the next command without waiting for the temperature to be reached.
    M109 Sets the extruder temperature, but waits until the target temperature is reached before proceeding with the next command.
    M140 Sets the bed temperature to a specified value and proceeds without waiting for the temperature to reach the target.
    M190 Sets the bed temperature and waits for the target temperature to be reached before executing the next command.
    M106 Turns on the cooling fan at a specified speed.
    M107 Turns off the cooling fan.

    These commands play a vital role in 3D printing as they enable precise control over the manufacturing process. Mastery of G-Code commands can help unlock the next level of 3D printing.

    Writing G-Code for 3D Printing

    In this section, we will explore the process of creating custom G-Code for 3D printing and understanding parameters and variables used in programming. We will also discuss how to generate G-Code using slicing software.

    Creating custom G-Code

    To take your 3D printing skills to the next level, you can create your own custom G-Code. Here’s how:

    1. Understand the structure: G-Code commands follow a specific syntax and structure. Familiarize yourself with the format so that you can write accurate code.
    2. Identify the parameters: Each G-Code command has various parameters that control different aspects of the printing process. Determine which parameters you want to modify or customize.
    3. Use variables: Variables allow you to input dynamic values into your G-Code. You can use variables to control parameters like print speed, temperature, or layer height.
    4. Experiment with slicing software: Slicing software is used to generate G-Code from 3D models. Explore the settings in your slicing software and experiment with different configurations to achieve desired results.
    5. Test and refine: Once you have written your custom G-Code, test it on your 3D printer and observe the results. Make adjustments as needed to improve the outcome.

    Understanding parameters and variables

    In 3D printing, parameters and variables play an important role in G-Code programming. Parameters are like instructions that define specific settings or values for a print job. For example, you can set the layer height, extruder temperature, or print speed as parameters.

    Variables, on the other hand, allow you to store and manipulate data during the printing process. They can be used for calculations or to keep track of certain values. By understanding how parameters and variables work in G-Code, you can customize your prints and fine-tune your settings for better results.

    Generating G-Code using slicing software

    Generating G-Code is an important step in 3D printing, and it can be done using slicing software. Slicing software takes your 3D model and translates it into layers that the printer can understand. Here are some key points about generating G-Code using slicing software:

    1. Slicing software analyzes your 3D model and generates a toolpath for the printer to follow.
    2. It determines factors like layer height, print speed, and infill density.
    3. You can adjust various settings in the slicing software to customize your print, such as choosing different infill patterns or adding supports.
    4. Once you’re satisfied with the settings, you can slice your model and export it as a G – Code file.
    5. The G – Code file contains all the instructions for the printer, including movements, temperatures, and extrusion rates.
    6. After generating the G – Code file, you can transfer it to your 3D printer via USB or an SD card.
    7. Some popular slicing software options include Ultimaker Cura, PrusaSlicer, and Simplify3D.
    8. It’s important to double-check your sliced G-Code before printing to ensure everything looks correct.
    9. If you want to make changes to your print settings or try different configurations, you can simply adjust them in the slicing software and regenerate the G-Code file.
    10. Generating G – Code using slicing software is a crucial step in preparing your 3D models for successful prints.

    Important G-Code Commands for 3D Printing

    Learn about key G-Code commands like G0 and G1 for motion control, as well as M104 and M109 for temperature control in 3D printing. Master these commands to enhance your printing experience!

    G0 & G1: Linear motion

    G0 and G1 are important commands in G-Code for controlling the movement of the 3D printer. These commands control the linear motion, which means how the printer head moves around while printing.

    G0 is used when we want to move quickly without printing, while G1 is used for slow and precise movements during actual printing. By using these commands, we can tell the printer where to start and stop printing on each layer.

    They help ensure accurate placement of each layer, resulting in high-quality prints. Understanding how to use G0 and G1 is crucial for achieving successful 3D prints with smooth and precise movements.

    G90 & G91: Absolute & relative positioning

    G90 and G91 are important commands that control how the 3D printer moves. When using G90, the printer will move based on absolute positioning. This means that coordinates are measured from a fixed point on the printer.

    On the other hand, when using G91, relative positioning is used. This means that movement is based on the current position of the printer head. These commands allow for precise control over where the printer goes and how it moves during printing.

    By understanding and using these commands correctly, you can ensure accurate and reliable prints with your 3D printer.

    G28 & G29: Auto home & bed leveling

    G28 and G29 are important G-Code commands for 3D printing that automate the process of home position and bed leveling. When you use the G28 command, it tells your 3D printer to move the print head to its “home” position, ensuring that it starts from a known and consistent starting point.

    This is useful for calibrating your printer before each print. On the other hand, the G29 command initiates an automated bed leveling process, where sensors or probes on your printer measure and adjust the height of different areas of the print bed.

    This ensures that your prints adhere properly to the bed surface, resulting in better quality prints overall. Understanding and using these commands correctly can greatly improve your 3D printing experience by simplifying setup and optimizing print quality.

    M104, M109, M140, & M190: Temperature control

    Temperature control is crucial in 3D printing to ensure the quality and accuracy of your prints. The M104, M109, M140, and M190 commands are used to control the temperature of different components in the printer.

    The M104 command sets the extruder temperature, while the M109 command waits for that temperature to be reached before continuing with the print. On the other hand, the M140 command sets the bed temperature and can be followed by an optional S parameter to specify a specific temperature value.

    Similarly, the M190 command waits for the bed to reach its set temperature before proceeding.

    These commands give you precise control over how your printer heats up during printing, allowing you to achieve optimal conditions for different types of filaments and materials. It’s important to understand these commands so you can adjust temperatures according to your specific requirements and achieve better print results.

    M106 & M107: Fan control

    One important aspect of 3D printing is controlling the fan. The M106 and M107 commands are used for fan control in G-Code. With the M106 command, you can turn on the fan and specify the speed using a value between 0 and 255.

    For example, M106 S150 will set the fan speed to 150 out of 255. On the other hand, if you want to turn off the fan completely, you can use the M107 command. Fan control is crucial for cooling down printed layers quickly, which helps prevent warping and improve print quality overall.

    Terminal Inputs and Outputs

    Learn how to send and edit G-Code commands, as well as monitor your print progress in real-time. Discover the power of terminal inputs and outputs in 3D printing!

    Sending and editing G-Code commands

    To control your 3D printer, you can send G-Code commands. These commands tell the printer what to do. Here’s how you can send and edit G-Code commands:

    1. Connect your computer to the 3D printer using a USB cable.
    2. Open a terminal program or software that allows you to communicate with the printer.
    3. Type in the G – Code command you want to send and press enter.
    4. The printer will execute the command and perform the desired action.
    5. To edit a G – Code command, simply modify the command in the terminal program and resend it.

    Monitoring print progress

    To ensure a successful 3D print, it’s important to monitor the progress of your print job. Here are some key points to keep in mind:

    1. Check the status: Regularly check the display screen or software interface of your 3D printer to see the current status of your print job.
    2. Observe the layers: Watch as each layer is printed to make sure they are adhering properly and there are no issues like gaps or warping.
    3. Monitor temperatures: Keep an eye on the extruder and bed temperatures to ensure they remain within the recommended range for your filament material.
    4. Look for errors or anomalies: If you notice any strange noises, unusual movements, or error messages, pause the print and investigate the issue before proceeding.
    5. Document progress: Take notes or pictures of each stage of the print process so you can refer back to them later if needed.


    In conclusion, understanding G-Code commands is crucial for anyone interested in 3D printing. This beginner‘s guide has covered the basics of G-Code and introduced the most important commands used in 3D printing.

    By mastering G-Code, you will have greater control over your prints and be able to unlock new possibilities in the world of 3D printing. Start experimenting with G-Code on your own printer and see what amazing things you can create!


    1. What is G-Code and why is it important in 3D printing?

    G-Code is a programming language used to control 3D printers and tell them how to move, extrude filament, and perform other actions. It’s important because it allows users to create complex prints with precise instructions.

    2. How can I learn to understand G-Code for 3D printing as a beginner?

    As a beginner, you can start by studying the basic commands of G-Code and their meanings. There are online tutorials, videos, and resources available that explain each command step-by-step.

    3. Can I modify the G-Code of existing 3D models?

    Yes, you can modify the G-Code of existing 3D models if you have knowledge of the programming language. However, caution should be exercised as any changes made may affect print quality or functionality.

    4. Are there software programs that generate G-Code automatically for 3D printing?

    Yes, there are various slicing software programs available that can automatically generate G-Code based on your input settings and preferences. These programs make it easier for beginners to prepare their models for printing without having to manually write G-Code from scratch.

    Rush Chapman
    ( Founder )

    Hello, my name’s Rush Chapman. I’m a 3D printing enthusiast. I started this site to help people choose 3D printing projects and select the best 3D printer for your needs, whether you’re a hobbyist or a pro!