🧩 Lesson: Generating and Reading G-code

🧠 Focus: Understanding how slicer software generates G-code and how to read or modify it for better control over your 3D prints.

✅ Lesson Summary

G-code is the language your 3D printer understands. It tells your machine exactly where to move, how fast, at what temperature, and more. This lesson explains how G-code is generated from slicers, what key commands mean, and how to read or troubleshoot simple G-code scripts.

🎯 Learning Objectives

By the end of this lesson, learners will be able to:

• Understand what G-code is and why it’s essential to 3D printing

• Identify the steps slicer software takes to generate G-code

• Open and read basic G-code files

• Recognize and explain common G-code commands

• Modify or troubleshoot G-code for specific print outcomes

📘 Lesson

🟪 1. What Is G-code?

Definition: G-code is a set of instructions that tells your printer how to build your object—including motion, temperature, fan control, and extrusion.

Each line in a G-code file is a command, often starting with G or M, followed by values for axes (X, Y, Z), feedrate (F), and extrusion (E).

📂 File Extension: .gcode for FDM printers, .g, .gx, .gcode for many others.
🧪 Resin printers (like Chitubox or PreForm) use proprietary sliced formats instead.

🟧 2. How Slicers Generate G-code

When you slice a 3D model, the software:

1. Converts the STL or 3MF model into layer data

2. Applies print settings: speeds, temperatures, retraction, infill, supports

3. Converts these into machine instructions (G-code)

4. Outputs a .gcode file readable by your specific printer firmware (Marlin, Klipper, etc.)

🟨 3. Common G-code Commands Explained

💡 ; is used to insert comments. These are ignored by the printer but helpful for humans.

🟩 4. Reading a Simple G-code File (Example)

🛠️ These commands are usually part of your slicer’s Start G-code script, and can be customized per printer.

🟥 5. Modifying or Customizing G-code

Customizations are often needed for:

• Changing nozzle or bed temps

• Inserting filament change (e.g., M600)

• Pausing at a layer (e.g., G1 Z10nM0)

• Retraction tuning or purge lines

Use a text editor (like Notepad++, Sublime Text) to edit .gcode files.

⚠️ Always back up the original G-code file before editing manually.

🧠 Summary

G-code is the command language of your 3D printer. While slicers handle most of the heavy lifting, understanding G-code helps you:

• Troubleshoot printing issues

• Customize printer behavior

• Add special functionality like color changes or pauses

• Learn how your printer actually interprets models