Spline to Polyline Converter

Why convert splines to polylines?

A SPLINE entity in a DXF file is a smooth NURBS curve defined by control points and knot values. It is mathematically exact and great for CAD, but a lot of maker tools, Mozaik especially, LightBurn's older importers, cheap vinyl plotters, almost every entry-level CAM package, simply skip SPLINE entities or ignore them with no warning. The result is a DXF that looks perfect in your source software and comes out empty on the laser bed.

Converting splines to polylines fixes this. A polyline is just an ordered list of straight segments (or short arcs). Every DXF reader on the planet handles polylines, so a flattened file cuts everywhere.

How polyline flattens a spline

When you drop a DXF here, we parse it with the ezdxf library, locate every SPLINE entity, and sample it with a chord tolerance of 0.05 mm. Chord tolerance is the maximum distance a straight segment is allowed to deviate from the true curve. At 0.05 mm the deviation is smaller than any CO2 or diode laser kerf, so the cut is visually indistinguishable from the original.

The output is written as an R12 ASCII POLYLINE by default, which is the one shape every DXF reader accepts. If you need the smaller R2000 LWPOLYLINE format for modern CAM, flip the switch above before clicking Fix.

What else gets fixed in the same pass

• Open polylines are detected and closed when endpoints sit within tolerance.
• Duplicate line segments on top of each other are merged.
• Zero-length segments are dropped.
• Self-intersecting closed polylines are flagged so you can see them before cutting.
• TEXT, MTEXT, HATCH and INSERT entities are removed because they do not cut.

FAQ