Guides

How to prepare a DXF for laser cutting

Most files that get stuck at upload fail for the same reasons: the wrong unit, text that is still text, lines that should not be cut, or an outline with a gap. This guide shows how to export the DXF from Fusion 360, FreeCAD and Inkscape so it works the first time, and what the messages on the upload page mean.

The short version

  • Draw at 1:1 scale in millimetres.
  • Only the cut outline goes in the file: no dimensions, frames, title blocks or construction lines.
  • The outer contour is one closed line, with no gaps and no duplicate lines on top of each other. Holes and cut-outs sit inside it.
  • Draw curves as arcs and circles where you can: they stay editable as such in the sketcher. Splines and ellipses work too.
  • Convert text to paths or outlines before you export.
  • One part per file.
  • Save as ASCII DXF. We cannot read a DWG or a binary DXF.

What we read from a DXF, and what we skip

The import takes lines, arcs, circles, ellipses, splines and polylines, including polylines with arcs in them. Blocks are expanded and their contents placed where they belong, mirrored blocks included.

Splines and partial ellipses come in as short straight segments that stay within 0.05 mm of the curve. They cut cleanly, but in the sketcher they are many small lines rather than one curve you can change as a whole.

Text, hatching and dimensions are skipped. If text, hatching or anything else that might belong to the part is left out, the upload page says so before the drawing opens.

Lines on the DEFPOINTS layer and lines with a dashed, dash-dot or dotted linetype count as construction lines and are not cut. Centre lines can stay in, as long as they are drawn as centre lines. A frame of solid lines, on the other hand, gets cut along with the part.

The import reads the unit from the file. If there is none, it assumes millimetres. The upload page shows the detected unit before you import, and lets you change it.

DXF from Fusion 360

  1. If the part is already a 3D body, create a new sketch on its flat top face and bring the face in with Project (P key). The sketch then holds exactly the outline and the holes, nothing else.
  2. If you draw in 2D, keep the cut outline in a sketch of its own. Dimensions and construction geometry stay in another.
  3. Right-click the sketch in the browser and choose Save As DXF.
  4. Fusion writes freeform curves as splines. They come in as short straight segments, which cut cleanly but can no longer be changed as one curve in the sketcher. Use arcs where you may want to adjust a radius later.
  5. Fusion saves in the document's unit. Check on the upload page that millimetres was detected.

DXF from FreeCAD

  1. If the part is a sketch in the Sketcher, use that sketch. For a 3D body, use Shape2DView in the Draft workbench to make a projection from above and export that.
  2. Select only the sketch or the projection in the tree, not the whole body.
  3. File > Export, file type Autodesk DXF 2D (*.dxf).
  4. FreeCAD works in millimetres, so the unit is right without anything else to do.

DXF from Inkscape

  1. Set millimetres as the unit in Document Properties and draw at full size.
  2. Select everything and use Path > Object to Path to turn text, rectangles and circles into paths. Text that is still text does not come through.
  3. The laser follows the path line itself; stroke width does not matter. If you drew a shape as a thick stroke only, turn it into an area with Path > Stroke to Path.
  4. Save As, file type Desktop Cutting Plotter (AutoCAD DXF R14). In the dialog, choose millimetres as the base unit.
  5. Depending on version and settings, Inkscape scales the DXF wrongly. Measure the part after the import. If it is 3.78 times too large, set the scale factor on the upload page to 0.2646.

Upload messages and what they mean

“Failed to import DXF file”

The file is not a readable ASCII DXF. Usually it is a binary DXF or a renamed DWG. Save the drawing as DXF again in your program and choose ASCII if it offers the option.

“DXF truncated: only the first 11000 entities were imported”

The file is made of a great many small pieces. That comes from hatching, from text broken into tiny segments, or from curves flattened too finely. Delete hatching, use a larger flattening value, or upload a STEP file for freeform parts.

The part is far too large or too small

The unit is wrong. Without one in the file we assume millimetres. If the part is 25.4 times too large, it was drawn in inches. Pick the right unit before importing or enter a scale factor.

Curves, holes or lettering are missing

Lettering that is still text is skipped, and the upload page says how many text objects were left out. Convert them to paths or outlines before exporting. Missing curves or holes are usually on the DEFPOINTS layer or drawn with a dashed linetype, so they count as construction lines. Or they are of a kind the import cannot read, such as a region: the upload page lists those too.

“Must be a single closed contour”

This one appears after the import, in the manufacturability check. The outer contour has a gap, two lines lie on top of each other, or the file holds several parts side by side. Close the gaps, delete duplicate lines and put each part in a file of its own.

Lines that should not be cut are in the part

A frame, title block or dimension lines drawn as solid lines. Delete them before exporting or move them to the DEFPOINTS layer.

“No flat face found in this STEP file”

STEP only. We cut flat parts from a sheet, so the model has to be flat and the same thickness everywhere. Bent or milled parts cannot be reduced to an outline.

Check after the import

After the import the drawing opens in the sketcher. There you can still change dimensions, add holes or delete lines. Once a material is chosen, the manufacturability check on the right shows whether the contour is closed and whether holes, bridges and edge distances are large enough for the material and thickness.

The minimum sizes per material are in the design guidelines and on every material page. A part can be at most 1150 × 550 mm.

If the file still does not come through cleanly, send it to us. We will look at it and tell you what is wrong.

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