Importing DXF files into FastCAM without errors

Most “bad DXF” problems in FastCAM, and in plasma CAM generally, come down to a handful of causes. A file can look perfect on screen and still refuse to make a part, cut at the wrong size, or make the torch stutter. Here’s what to check before the file ever reaches the table.

1. Every profile must be closed

CAM programs build parts from closed loops. A gap of a few thousandths between two lines, which you’ll never see on screen, means the software can’t tell inside from outside, so it can’t apply kerf or lead-ins. Traced and hand-drawn files are the usual culprits. Join or close all profiles before import.

2. No splines

Splines (smooth curves from Illustrator, Inkscape and many “image to vector” tools) are read badly or not at all by many CAM packages, or get chopped into thousands of tiny lines. Convert curves to lines and arcs first.

3. Use a widely supported DXF version

AutoCAD R12 (AC1009) is the safest format: nearly every CAD/CAM program reads it. Newer versions mostly work too, but R12 removes a whole class of import surprises.

4. Get the units right

DXF files don’t reliably say whether they’re in inches or millimetres. When the import asks, pick the units the file was drawn in. A part that imports 25.4× too big or too small is a units mix-up, not a scaling problem.

5. Remove duplicate and overlapping lines

Two lines on top of each other make the torch cut the same path twice (a wider kerf, a burned edge, wasted time), or confuse part detection. Delete duplicates and tiny stray segments.

6. Fewer, smoother segments

A curve made of hundreds of tiny straight segments makes the machine accelerate and decelerate constantly, which leaves a rough, faceted edge. True arcs let it move smoothly at full cut speed.

Before you cut: a quick checklist

• Import at the right units and measure one known dimension.
• Every part shows as a closed profile with its holes recognised.
• Kerf set once, either in the CAM or baked into the DXF, never both.
• Holes and inside features are cut before the outline.
• Lead-ins are on the scrap side (outside outlines, inside holes).