Lasers read vectors and rasters, not meshes. Here is the honest workflow, plus the two places a mesh still earns its keep.
Convert an image to STLIf you searched for an STL file for laser engraving, you already hit the wall. You found a mesh, opened your laser software, and the import dialog greyed it out. LightBurn, LaserGRBL and xTool Creative Space take SVG, DXF, PNG, JPG and BMP. None of them read STL. A laser head moves in X and Y and fires a beam; it has no Z axis to follow a triangle mesh. The file format is not the problem. The machine is 2D.
What the machine wants instead is either a vector path or a raster image. Vector formats, SVG and DXF among them, describe lines and fills, so the laser can follow a contour or fill a shape. Raster formats such as PNG, JPG and BMP describe pixels, so the laser can vary power across a photo. Your laser software lists those in the import dialog. It will not list STL, OBJ or 3MF, because those describe surfaces in three dimensions and the head never leaves the plane.
An STL still earns its place in two jobs. The first is CNC relief: a ball nose cutter does move in Z, so a height map exported as a mesh becomes a carved panel. The second is a jig. Print a holder that sets your tile, coaster or knife blank at the same spot every run, and your laser work stops drifting between jobs. The mesh is a tool for the setup, not the file the laser burns.
Three routes reach the same place: a workpiece with the image on it, made on the machine that can carry it.
Export the image as a greyscale PNG at the final physical size, around 300 dpi, then invert it so dark pixels mean more power. Laser software maps brightness to power and the beam does the rest. This holds gradients and photographic shading that no traced outline carries.
Autotrace the image, or draw over it by hand, then simplify the node count until curves are clean. Set strokes as cut lines and fills as engrave areas before export. Logos, lettering and single-colour shapes survive this route better than photos.
Convert the image to STL when the job is a CNC relief or a printed fixture. A 2 to 4 mm relief depth gives the cutter something to follow; a jig with 0.2 mm clearance holds the blank square. Neither one is a laser file, but both jobs need the third dimension a laser cannot provide.
A raster engrave is a grid of dots. At 300 dpi across a 100 mm tile that is about 1180 pixels of width, and the laser's spot decides how many of them survive: a diode module burns a line near 0.08 mm wide, a CO2 tube nearer 0.15 mm. Greyscale mode varies power per pixel and gives real tones. One-bit dithering trades those tones for a spray of dots, which reads as grey from a step back and as noise from close up.
A traced SVG behaves like a drawing, not a photo. Every stroke is a cut path with a kerf, usually 0.1 to 0.2 mm wide, so a hole drawn at 5 mm comes out nearer 4.8 mm. Fills engrave, strokes cut, and the order you stack them decides what gets cut free first. A few hundred nodes cut cleanly; a few thousand nodes from an untidy autotrace will slow the run and leave scorched corners.
An STL from an image is a surface, so it carries height instead of grey. On a 0.4 mm nozzle printer, a 2 mm relief needs about ten layers at 0.2 mm, and the mesh has to be watertight or the slicer will leave gaps. It prints in one colour, because STL stores geometry only and no texture. Scale it in millimetres before you export, or the finished jig will not fit the blank it was drawn for.
Five settings decide whether the run looks deliberate or muddy.
| Setting | Typical value | What it changes |
|---|---|---|
| Raster resolution | 300 dpi | How much photo detail the beam can resolve |
| Image mode | 8-bit greyscale | Whether brightness maps to laser power |
| Invert | On | Makes dark pixels the burned ones, not white |
| Trace threshold | 0.5, adjust by eye | Which tones collapse into vector edges |
| Mesh units | Millimetres | Whether an exported STL prints at the size you drew |
Nothing in that table produces a mesh. Resolution, mode, invert and threshold all act on a raster or a vector, which is what a laser reads. The units row is the only one belonging to the STL side of the job, and it matters only when the file leaves for a printer or a CNC.
If the mesh is the part you actually need, this tool turns a JPG, PNG, SVG, HEIC or WebP into an STL in the browser. It is free to use, needs no account, and runs on Windows, macOS, Linux, Android and iOS. The output is geometry only, so no colour or texture travels with it. Keep it away from the laser: this file is for the printer or the CNC.
It depends on the job. SVG or DXF is best for cuts, outlines, lettering and any shape you want as a clean line or a filled area, because both describe paths rather than pixels. For photographs and shading, a greyscale PNG or JPG at 300 dpi gives the laser more to work with. STL is not on either list.
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