Using SVG Files for Laser Cutting and CNC Projects

Scalable Vector Graphics (SVG) are not just for web browsers. Because an SVG file contains exact mathematical coordinates, it is the perfect language for communicating with machines that move in physical space. Whether you are operating a desktop Glowforge, a massive industrial CO2 laser, or a CNC router, SVG files are the bridge between your digital design and your physical product.

However, preparing an SVG for a laser cutter is very different from preparing one for a website. A web browser just wants to paint the screen; a laser cutter needs explicit instructions on whether to burn a surface, score a line, or cut completely through the material. In this guide, we will cover the essential rules for formatting SVGs for maker hardware.

Understanding the Three Operations: Cut, Score, and Engrave

Laser software (like LightBurn or Glowforge App) reads the styling attributes of your SVG to determine what the laser head should do. By industry standard, the software looks at the stroke (outline) and the fill (solid color) of your shapes.

• Cutting (Vector Cut): The laser fires at high power and moves slowly along the exact mathematical path, burning entirely through the wood or acrylic. Design Rule: To define a cut line, give the shape a very thin Stroke (usually 0.1pt or Hairline) and NO Fill.
• Scoring (Vector Engrave): The laser fires at a lower power, moving quickly along the path to draw a permanent line on the surface without cutting through. Design Rule: Similar to cutting, use a thin Stroke, but designate it with a different color (e.g., Blue for score, Red for cut).
• Engraving (Raster Engrave): The laser head moves rapidly back and forth across the material like a standard inkjet printer, burning the surface wherever there is a solid shape. Design Rule: To define an engraved area, give the shape a solid Fill and NO Stroke.

Color Coding Your SVG

One of the best practices when designing an SVG for a laser cutter is to use a strict color-coding system. Modern laser software will automatically split different colors into different "layers" or "operations".

For example, if you are designing a custom wooden keychain, you might use:

• Black Fill: The logo and text in the center (Engrave).
• Blue Stroke: A decorative border etched into the wood (Score).
• Red Stroke: The outer silhouette of the keychain and the hole for the ring (Cut).

By organizing your SVG with these specific colors before exporting, the laser software will instantly recognize your intentions, saving you from manually assigning operations to every single line.

Crucial Prep: Converting Text and Strokes

Laser cutters do not understand typography or stroke weights. If you send an SVG with a live font, the laser software might crash or ignore it. You must select all text and convert it to paths (outlines).

Similarly, laser cutters ignore the "thickness" of a stroke in an SVG. If you draw a path and give it a massive 10pt stroke because you want a thick line, the laser cutter will still only trace the infinitely thin mathematical center line. If you want a thick line to be engraved, you must use your design software's "Expand" or "Outline Stroke" tool. This converts the single thick path into a solid, filled shape with an outer boundary that the laser can engrave.

Connecting Overlapping Shapes (Pathfinder/Weld)

If you draw two overlapping circles in an SVG and give them a red stroke to indicate a cut line, the laser will literally cut out both full circles, slicing right through the overlapping area and ruining your piece.

Before exporting your SVG, you must "Weld" or "Unite" overlapping cut shapes. This merges the individual objects into one single, continuous outer path, ensuring the laser only cuts the outer perimeter.

Conclusion

Laser cutting is an incredibly satisfying process, but it requires precision. By remembering to convert all text to paths, expand your thick strokes, weld your cut lines, and strictly color-code your fills and strokes, your SVG files will translate perfectly from the digital canvas to the physical material.