Why Your Laser Cut File Won't Cut: 9 File Errors and Fixes

When a cut goes wrong, the first instinct is to blame the machine and change the settings. More often the file is at fault, and no amount of power or speed will fix it. These are the nine file errors I fix most often, in the order you should check for them.

1. Duplicate lines

Symptom: some lines are darker or wider than others, edges are burnt, or the job takes longer than it should. Cause: two or more identical paths sit on top of each other and cut twice. Fix: use Delete Duplicates in LightBurn, or Path → Combine then remove overlapping segments in Inkscape or Illustrator.

2. Open paths

Symptom: a part stays attached to the sheet by a thin sliver. Cause: the outline is not a closed shape; there is a tiny gap between its start and end points. Fix: join the end nodes. Most programs can highlight open paths — check every cut shape.

3. Wrong colours or layers

Symptom: engraving is cut, cuts are scored, or some lines are ignored. Cause: colours in the file do not match the machine’s operations, or several near-identical colours (for example #FF0000 and #FE0000) are treated as different layers. Fix: set exact colours for cut, score and engrave, and move everything onto matching layers.

4. Text still as text

Symptom: text is missing or appears in the wrong font. Cause: the text is live type, and your computer does not have the font. Fix: convert text to outlines or paths before exporting.

5. Wrong scale

Symptom: everything is exactly 75% or 133% of the expected size, or tiny. Cause: DPI mismatch between programs, or the document was set up in pixels or inches. Fix: scale by the correct ratio and check a known dimension. The full explanation is in importing SVG files without scaling errors.

6. Details too small to survive

Symptom: thin parts burn away, snap or come out charred. Cause: features smaller than the laser can leave standing. Fix: keep solid areas at least 1.5 × the material thickness wide, or engrave fine detail instead of cutting it.

7. Islands with no bridges

Symptom: the centres of letters and shapes fall out. Cause: closed shapes inside holes with nothing connecting them. Fix: add bridges, use a stencil font, or engrave the detail. See turning a picture into a laser cut file.

8. Too many nodes

Symptom: the laser stutters, curves look faceted, or the file is slow to load. Cause: auto-traced paths or converted fonts with thousands of points. Fix: simplify the paths gently and compare against the original shape.

9. Joints that do not match the material

Symptom: slots too tight or too loose, boxes that do not close. Cause: the file was drawn for a different thickness, or without kerf compensation. Fix: adjust the slots for your material and compensate for kerf.

A 60-second check before every job

Open the file in your laser software and look at it in wireframe or outline view. Duplicates, open paths, stray points and fonts that did not convert all show up there. It takes a minute and saves a sheet of material. To avoid these errors from the start, follow how to design for laser cutting.

Questions

Why does my laser cut the same line twice?

There are duplicate lines in the file. Delete duplicates before cutting.

Why is part of my design not cutting through?

If the file is clean, look at the material: a warped sheet or a glue pocket in plywood. If only certain shapes fail, check they are closed paths on the cut layer.

Can you fix a file that will not cut?

Yes — cleaning and repairing files is a service in itself. Send the file and a description of what happens, and I will tell you what is wrong. See file repair.

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Every file in the catalogue is checked for all nine of these before release. If you have a file that is giving you trouble, send it over.