Preparing a DXF for laser cutting

1. Every contour must be closed

CAM software turns closed loops into cut paths. An outline with a 0.01 mm gap between two endpoints is not a loop — it is two lines that happen to nearly touch, and the nesting software will either refuse it or cut a path that never returns to its start.

This is the single most common rejection reason, and it is invisible on screen. Gaps come from drawing without snapping, from trimming that leaves a stub behind, and from exporting arcs that were never joined to their neighbours. Coobic avoids the class of problem entirely by forcing geometry onto a grid and exporting closed polylines, so endpoints coincide exactly rather than approximately.

2. Separate bend lines from cut lines

A bend line is not a cut. If it sits on the same layer as the outline, the shop has to guess — and the expensive version of that guess is a part cut in half along its fold.

Put bends on named layers. Coobic's export uses a convention that reads unambiguously in any DXF viewer:

Splitting by direction rather than using one BEND layer matters because the press brake operator needs to know which way each fold goes, and a flat drawing cannot show it otherwise.

Be aware that layer names are a convention, not a standard. Different shops expect different names, and a quoting portal that auto-detects folds may not recognise yours. If the bends matter, send a STEP file too.

3. Draw 1:1 in millimetres

DXF stores bare numbers. There is an $INSUNITS header value that says what those numbers mean, but plenty of CAM packages ignore it and assume their own default. A part drawn in inches and read as millimetres is 25.4 times too small, which is at least obvious; a part drawn at 1:2 scale is quietly half size, which is not.

Draw at full size in millimetres, and say so in the email. It takes one sentence and removes an entire failure mode.

4. Remove duplicates and construction geometry

Two identical lines on top of each other look like one line and cut like two — the beam runs the same path twice, burning the edge and doubling the time. Overlapping segments from copy-paste editing are the usual source.

Delete construction lines, centre marks, borders, title blocks, dimensions and annotation before exporting, or keep them on a layer you tell the shop to switch off. Anything left on a cut layer will be cut.

5. Avoid splines and text

Splines are the entity most likely to trip up older CAM software — some refuse them, some approximate them coarsely enough to leave visible facets. Convert curves to arcs and polylines first.

Text is worse, because a TEXT entity references a font that may not exist on the shop's machine. If a part needs engraving, convert the text to outlines and put it on a clearly named engraving layer.

Quick checklist

• Outline and every hole is a closed loop
• Bend lines on BEND-UP / BEND-DOWN, cuts on layer 0
• 1:1 scale, millimetres, stated in writing
• No duplicate or overlapping segments
• No construction geometry, dimensions or title block on cut layers
• No splines, no live text
• Material and thickness stated separately — the DXF cannot carry them

That last point catches people out. A DXF is pure 2D geometry: it has no idea what material it is, how thick it is, or how many you want. Put those in the email, every time.

Frequently asked questions