Guide

How to turn an image into a DXF for a laser cutter

A laser cuts along lines. A DXF file is a list of lines and curves with coordinates, with no colors to fill and no pixels. To get one from a PNG or JPG, you trace the image into closed outlines and save those outlines as DXF. The tracing is the hard part; saving is one menu.

What a good laser DXF has

• Closed outlines. Every shape you want to drop out of the sheet ends where it starts. An open path cuts a slit, not a piece.
• One line per edge. Edge-detection traces give two lines around every stroke (inside and outside edge), and the laser cuts both. For a cut-out, trace filled shapes, not edges.
• No dust. Every leftover speck is a tiny closed outline the laser travels to and burns.
• The right size. Older DXF versions don't reliably store units, so the same file can open as 100 mm or 100 inches. Check the width after import and scale it if needed.
• Holes and islands that make sense. The inside of an O is its own outline. If you cut it, the counter falls out. For stencils you may want bridges; for signs and ornaments you usually don't.

The free way: Inkscape

1. Open the image in Inkscape and select it.
2. Path > Trace Bitmap (Shift+Alt+B). Choose Single scan and Brightness cutoff. Move the threshold until the shapes you want are solid. Turn on Speckles with a size big enough to drop dust, plus Smooth corners and Optimize. Click Apply.
3. Move the trace off the image and delete the image. Set the width you want in millimeters in the toolbar.
4. Optional cleanup: Path > Break Apart to see each outline as its own object, and delete stray pieces.
5. File > Save As and choose Desktop Cutting Plotter (AutoCAD DXF R14). In the options, set the base unit to mm. Some laser software prefers the R12 variant, which Inkscape also offers.
6. Import the DXF into your laser software and measure it before you cut. Users have reported Inkscape DXF exports coming out at the wrong scale when units mix, so this check is worth the ten seconds.

In LightBurn

LightBurn imports DXF and SVG (File > Import) and puts shapes on layers by their color in the source file. A DXF from a trace usually lands on a single layer, which is what you want for a cut-out. If you also want to engrave the filled areas, import an SVG instead: a DXF carries no fills, so there is nothing to engrave.

LightBurn can also trace an image itself (Tools > Trace Image), which skips the DXF entirely if LightBurn is where you cut.

Kerf: why pieces come out a little small

The beam burns away a thin strip along every line, so a cut piece ends up smaller than the drawing by about half that width on each side, and a hole ends up bigger. For decorations it doesn't matter. For parts that must fit together (inlays, tabs, boxes), measure your own kerf with a test cut in the real material and offset the outlines by half of it.

With Cutline

Pick the LightBurn or Vinyl sign plotter preset. Cutline traces filled shapes (one line per edge), drops specks below the size you set, closes every outline and writes an R12 ASCII DXF of closed polylines, in the unit you chose, with curves flattened finely enough for a laser. The SVG for LightBurn puts cut lines in red and engraving in black, so they open as two layers. Before paying you can download a free one-color SVG test cut to check size and detail on scrap; the DXF and full-resolution files are $2 for that image.

• LightBurn documentation, Basic usage essentials (DXF and SVG import, color to layer mapping).
• Inkscape extensions, DXF14 export issue with scaling and different base units.