A laser cutter does not see your drawing the way you do. It follows paths, line by line, exactly as they sit in the file. So a DXF that looks perfect on screen can still cut badly: a slit where you wanted a hole, a part scaled to a fraction of its size, or every edge burned twice. Getting a clean cut is mostly about preparing the file correctly, and the rules are simple once you know them.
Why laser cutters want a DXF
Laser, plasma and waterjet cutting are 2D profile operations: the machine drives a beam along a path through a flat sheet. It needs that path as vector geometry, lines, arcs and polylines, not a picture. DXF is the standard way to carry exactly that. It was designed as an exchange format, so it opens reliably in LightBurn, the controllers most cutters use, and in every CAD tool, which is why most shops ask for it. Many also accept DWG or SVG, but DXF is the safest common denominator. For the full picture of where DXF sits next to DWG, STEP and PDF, see which file to send your manufacturer.
Cut shapes must be closed paths
This is the single most important rule. A closed path is a loop whose start and end points meet, so the cutter knows it is a profile to cut all the way around and drop out as a part. An open path is a line with two loose ends; the machine reads it as a slit and cuts a single stroke, not a shape.
- Cutting a part out? Every outline and every internal hole must be a closed loop.
- Scoring or engraving a line? An open path is exactly right, since you want a stroke, not a cut-out.
Open paths usually come from geometry that looks joined but is not: two endpoints sit a hair apart instead of snapping together. Most laser software can highlight open contours and join points within a tolerance. Run that check before you cut.
Get the units and scale right
A DXF stores coordinates as plain numbers. The unit those numbers mean, millimetres or inches, is not strictly enforced by the format, so the receiving software decides. That is how a part drawn correctly in inches ends up 25.4 times too small when it is opened as millimetres.
$INSUNITS header value), and say it in your message: “DXF, millimetres”. Then sanity-check one known dimension in the cutter's software before the job runs. Thirty seconds here saves a scrapped sheet.Clean up the geometry
A few tidy-up steps prevent most of the rest of the trouble:
- Remove duplicate lines.Two identical paths stacked on top of each other make the laser cut the same line twice, wasting time and scorching the edge. Use the software's delete-duplicates function.
- Close the gaps. Join endpoints that should meet so every cut profile is a true closed loop.
- Convert text to outlines. Text that is still live relies on a font the cutter may not have. Convert every label to vector outlines so it cuts as geometry.
- Strip embedded images. A DXF that merely contains a pasted bitmap has nothing to cut. The laser only follows vectors.
- Keep it to simple entities. Lines, arcs, circles and polylines import most reliably. Modern software handles splines well, but exploding them into polylines removes any doubt.
Separate cut, score and engrave
Most jobs are not all cutting. You might cut the outline, score a fold line and engrave a logo, each at a different power and speed. Shops normally separate those operations by layer or colour in the file, then map each one to a setting at the machine. Ask your cutter how they want it organised, then put cut lines, score lines and engraving on their own layers so nothing is ambiguous.
Remember the kerf is not in the file
The laser beam has width, typically around 0.1 to 0.2 mm, and it removes material as it travels. That width is the kerf. Your DXF holds the nominal path; kerf compensation is normally applied by the operator or the CAM software, not drawn into the file. You do not need to offset your lines, but you do need to design with kerf in mind: very thin tabs, tight slots and parts meant to press-fit can come out loose if you ignore it. When a fit matters, tell the shop, or cut a test piece first.
Starting from a photo or a logo
A laser cannot cut a JPG or PNG, because a photo is pixels and the machine needs vectors. The fix is to trace the image into vector outlines and export a DXF, then prepare that DXF with the rules above. Our free image to DXF converter does the tracing in your browser: drop in a logo or a high-contrast shape, tune the trace, and download closed DXF polylines ready to clean up and cut. It works best on flat line art; for the difference between tracing and a real measured drawing, see image to CAD and the best JPG to DXF converters.
The pre-flight checklist
Run through this before every laser job:
- Export or save as DXF (or the format your shop asks for).
- Every cut profile is a closed loop; scores and engraves are open on purpose.
- Units set and stated, and one known dimension checked at the machine.
- Duplicate lines removed and open gaps joined.
- Text converted to outlines; no embedded bitmaps.
- Cut, score and engrave on separate layers or colours.
- Fit-critical features flagged, with kerf in mind.
Tick those off and your file will cut the way it looks on screen, which is the whole goal. If you are still deciding which format to send in the first place, our guide to DXF, DWG, STEP or PDF covers it.
Frequently asked questions
What file format do laser cutters use?
Most 2D laser, plasma and waterjet cutters read DXF, and many also accept DWG, SVG or AI. DXF is the safest and most portable choice because it was built as an exchange format and opens in nearly every machine's software. Whatever the format, the cutter follows the vector paths inside it.
Do laser cutting paths need to be closed?
For anything you want to cut out as a shape, yes. A closed path tells the cutter where material starts and ends, so the part drops out cleanly. Open paths are read as a single line, which the machine will cut as a slit rather than a closed profile. Open paths are fine when you intend to score or engrave a line rather than cut a shape.
What units should a laser cutting DXF use?
Agree the unit with your cutter, but millimetres are the most common for laser work. A DXF does not strictly enforce a unit, so a file drawn in inches opened as millimetres comes out 25.4 times too small. Set the units explicitly and state them when you send the file.
Why does my DXF cut every line twice?
Almost always duplicate or overlapping geometry. When two identical lines sit on top of each other, the laser cuts the same path twice, which wastes time and can scorch the edge. Most laser software has a function to find and remove duplicate lines before cutting.
Can I laser cut from a photo or a JPG?
Not directly. A laser needs vector paths, and a photo is pixels. You first trace the image into vector outlines and export a DXF, then prepare that DXF as in this guide. A free in-browser tool can do the tracing step for you.