Are you new to CNC pen plotters and feeling overwhelmed by G-code? Don’t worry — this beginner-friendly guide explains everything you need to know about using G-code with the UUNA TEK 3.0 Pen Plotter. From understanding the basics to sending your first G-code file, this tutorial walks you through each step clearly so you can start creating smooth, precise pen-plotted artwork with confidence.
What Is G-code?
G-code (also written as Gcode or G-Code) is a universal programming language used in computer-aided manufacturing (CAM). It provides step-by-step instructions that tell machines how to move, operate, and perform tasks — such as cutting, milling, drilling, engraving, or plotting.
For pen plotters like the UUNA TEK 3.0 Pen Plotter, G-code guides the machine’s movement along the X, Y, and Z axes to accurately draw lines, curves, and text.
Originally developed by MIT in the 1950s, G-code has now become the industry standard for controlling CNC machines — and is widely used for modern pen plotters as well.
Think of G-code as a detailed recipe. Instead of relying on heavy vector files that might crash Inkscape or slow down your computer, the UUNA TEK 3.0 Pen Plotter can draw artwork faster and more efficiently when you send it clean G-code instructions.
Common G-codes Used in UUNA TEK 3.0 Pen Plotter
Below are the essential G-codes you need to operate the UUNA TEK 3.0 Pen Plotter. These are beginner-friendly and cover 95% of what you’ll use for plotting.
G00 – Rapid Move
Moves the pen quickly between two points without drawing.
Used when repositioning the pen before or after drawing.
G01 – Linear Interpolation
Draws straight lines from one point to another at a set feed rate (F).
Essential for almost all artwork and handwriting.
G20 / G21 – Unit Selection
- G20 = Inches
- G21 = Millimeters (recommended for plotters)
Most pen plotter G-code files are created in millimeters, especially for precision artwork.
G90 / G91 – Positioning Modes
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G90 – Absolute Positioning
Coordinates refer to exact points based on the machine’s origin. -
G91 – Incremental Positioning
Coordinates represent relative movement from the current location.
Tip: Most plotting workflows use G90 absolute mode for clean, predictable plotting.
Note: While there are many more G-codes in CNC machining, the ones listed above are all you need to get started with the UUNA TEK 3.0 Pen Plotter.
Software to Send G-code to the UUNA TEK 3.0 Pen Plotter
We recommend UGS (Universal Gcode Sender) because it is stable, easy to use, and works perfectly with UUNA TEK 3.0 Pen Plotter machines. It allows you to:
- connect your plotter
- send G-code in real time
- visualize tool paths
- control machine movement
Download UGS from the official page:
https://winder.github.io/ugs_website/download/
Create Your First Artwork Using G-code
Try your first pen plotter artwork using the G-code file provided.
- Size: A5
- Recommended pen: 0.4 mm fineliner
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G-code file download link:
https://drive.google.com/file/d/1tyoX9kEyxbqLFSVveA8F3PMiuciasH8h/view?usp=sharing
Steps to Plot
Step 1: Open Universal Gcode Sender
Launch the UGS software on your computer.
Step 2: Turn on the Plotter and Connect via USB
Power on your UUNA TEK 3.0 Pen Plotter and plug it into your PC using the USB cable.
Step 3: Connect to the Machine
In UGS, select the correct COM port, then click the Connect button.
Step 4: Load the G-code File
Click Open File (upper-left corner) and select the G-code file you downloaded earlier.
Step 5: Prepare Paper & Pen, Then Start Plotting
- Place A5 paper on the machine
- Set pen height to 3 mm
- Move the pen to the upper-left corner of your paper
- Click the Play button to start plotting
Important: Do not change the baud rate.
Example Results
Below are images demonstrating the UGS interface and artwork created using the UUNA TEK 3.0 Pen Plotter.
This article was contributed by @Mandeep Singh.