SVG to DXF for laser cutting: sizes, curves, fills and strokes from Inkscape, Illustrator and CorelDRAW

Units: 96, 72 and the viewBox

CSS and SVG define 1 in = 96 px and 1 pt = 1/72 in. The root of an SVG can carry a width and a height with a unit (mm, in, pt, px…) and a viewBox: four numbers giving the rectangle of drawing coordinates that is fitted into that width and height. A width or height without a unit is in px. Illustrator works at 72 px per inch: in Adobe's community forum, a 10 cm square exported as 283.46 px where 377.95 px was expected — 72 against 96 per inch, so a 96-per-inch program shows it at 75 %. Adobe's community experts suggest unchecking Responsive in the SVG export, which writes fixed dimensions.

Zorocut treats a file as an Illustrator file when it finds the comment “Generator: Adobe Illustrator” in it. If some tool has stripped that comment, an Illustrator file in px is read at 96 per inch and comes in at 75 % — which is why you measure one known dimension.

Curves

• Circles, and SVG arcs with equal radii, stay true arcs; so do rounded rectangle corners with equal radii.
• Béziers and ellipses are fitted with arcs and lines within 0.01 mm and listed as approximated in the pre-cut check.
• If you export a DXF from Inkscape instead, each Bézier segment becomes its own SPLINE and a document in px is written without a unit at 96 px per inch — see DXF units and splines and arcs.

Fills, strokes, text, clips

The Inkscape commands are in its own manual: Object to Path turns a shape into a path, Stroke to Path turns a stroke into its own object, Union keeps the common outline, Intersection keeps only what all selected paths cover, and a clip only hides what lies outside it — the hidden part is still in the file.

Layers

In an Inkscape SVG, each layer's name becomes a layer name; in other SVGs, the id of each top-level group does. The names decide the process the same way as in a DXF: MARK, ETCH or SCRIBE is marking, ENGRAV engraving, names containing TEXT, DIM, BORDER and the like are left out, everything else is cut. Colours are not used. (SheetCAM, by contrast, can turn colours into layer names on SVG import.)

By program

• Inkscape: set the document unit to mm and save as Inkscape SVG, which keeps the layer names Zorocut reads. Its DXF exporter converts text to paths by itself but writes px documents without a unit.
• Illustrator: draw in mm, uncheck Responsive in the SVG options, use Create Outlines for text. A part at 75 % is the 72/96 mismatch.
• CorelDRAW: we found no documentation of how its SVG export sets the size. Export a 100 mm test square once and check that it reads as 100 mm.
• Raster logos (PNG, JPG) hold nothing to cut until someone redraws them as vectors. Zorocut reads DXF and SVG only: save AI, EPS, PDF or CDR files as SVG first.