All articles · 2026-09-18

Getting a cuttable DXF out of an image (CNC, laser and vinyl)

A cutter follows closed paths. What that means when tracing a part from an image, why scale is what everybody gets wrong, and how to check a DXF before cutting.

A cutting machine — router, laser, plasma or vinyl plotter — does exactly one thing with your file: it follows paths. Every path it can see, it will try to cut. That single fact explains most of what goes wrong when a file made for a screen is sent to a machine.

Here is a mounting bracket outline, the sort of thing that arrives as a picture in a PDF or a photo of a printed drawing.

A bracket profile with two bolt holes: on the left the pixelated source image; on the right a clean two-colour vector with a smooth radius.
Left: a 160-pixel source. Right: Logo mode, two colours — 2 paths, 34 nodes. The outer profile and the two holes are separate closed paths, which is what a cutter needs.

Closed paths, and only the paths you want cut

Each shape must be a closed loop. An outline with a gap in it is not a cut — most machines will either refuse it or cut a line that goes nowhere. Holes must be their own closed paths inside the outer profile, so the machine knows to cut them out rather than around them. Curvora writes closed geometry by default; what to check is that there are no extra paths you did not mean, from a border, a watermark or a scanning artefact.

The curved shoulder of the bracket magnified: on the left a visible staircase of pixels; on the right a smooth continuous arc.
The radius where the arm meets the body. A staircase like the one on the left becomes a staircase in the cut — visible in aluminium, and audible in the machine.

Scale is the part that costs money

An image has no size. It has pixels, and a vector traced from it has whatever units the export decided on. Before anything goes on a machine, set the real dimension of one known feature — a bolt hole diameter, an overall length — in your CAM software, and scale the whole drawing to match. Doing this by eye, or trusting the file to arrive at the right size, is the single most common way a first cut gets scrapped.

A checklist before the machine

  • Open the DXF in your CAM software and look for duplicate or overlapping paths — cutting the same line twice burns the edge
  • Confirm every hole is inside the profile it belongs to, not stacked on top of it
  • Set the scale from a measured feature, not from the file
  • Check the smallest internal radius against your tool: a 6 mm cutter cannot produce a 2 mm inside corner, whatever the drawing says
  • Cut one in scrap before cutting one in material

What DXF does and does not carry

Curvora writes DXF as polylines — the outlines, in a form every machine reads. It does not carry colour, layers by cut order, kerf compensation, lead-ins or tabs: those belong to your CAM software, which knows your machine and your material. The vector’s job is to give that software accurate geometry to start from.