How to convert an image to DXF for CNC plasma cutting

Customers hand you a logo off their truck door, a phone photo of a sketch, or a picture they found online, and they want it in steel. Here’s how to get from that picture to a DXF your table will cut cleanly, whatever software you use.

1. Start with the right picture

• High contrast wins. Black shapes on white (or the reverse) trace almost perfectly. Logos and silhouettes are ideal.
• Bigger is better. At least 1000 px across. A tiny web thumbnail loses detail no software can invent.
• Sketches work if the lines are dark and continuous. Photograph them flat, in even light.
• Photos need to become bold, stencil-style art first. Busy photos turn into thousands of specks.

2. Trace it, and set the real size

Tracing turns the picture’s dark and light areas into closed outlines. Decide which is metal: usually the dark shapes, but a white-on-black logo is the other way round. Then set the finished size in inches or mm. Everything else, like minimum hole size, depends on the real size and your plate thickness.

3. Fix what won’t cut

• Islands: the centres of letters like O, A, B, D, P, R and Q are separate pieces. Without a bridge connecting them, they fall out and your sign reads “CL SED”. Bridges about 1/4" wide are typical for sign work.
• Small holes: holes smaller than the plate thickness cut badly on plasma. Enlarge them, fill them, or mark and drill.
• Thin lines: sketch lines narrower than a couple of kerf widths burn away. Thicken them first.
• Specks and stray bits: delete them. Every one is a pierce and a part that falls through the slats.

4. Set the cut order

Cut holes and inside details first, outlines last, so the part doesn’t shift once it’s cut free. Fewer, shorter rapid moves between pierces save real time on big signs.

5. Export a clean DXF and test cut

Export an AutoCAD R12 DXF with closed profiles, and use true arcs rather than splines or thousands of tiny lines. Import it, measure one known dimension to confirm the units, then cut a small test piece before committing a full sheet. (See our FastCAM import checklist and the kerf chart.)