Designing a Celtic Knot in Blender and Engraving It on Slate
The add-on has been out a few days now, and the question I keep getting is a
fair one: what do you actually do with it? So here’s the whole thing, from an
empty Blender scene to a coaster with a cup of tea on it, in under seven
minutes and with nothing cut out.
Sizing it to the object
The slate blanks are 100mm square with rubber feet, and I wanted the engraved
area at about 88mm so there’s a margin of honest rough slate around the
pattern. A four-by-four grid at 20mm cells gives 80mm, which sits inside that
comfortably and keeps the arithmetic in my head rather than on paper. That’s
the whole of the setup: pick a cell size, pick a grid.
The part that’s actually design
Then the breaks. A plait is just a plait; it’s the breaks that turn it into a
knot, and where you put them is the design decision. In the video you can watch
me set one, dislike it, clear it and try somewhere else — which is the honest
version of how this goes. When it looked right I checked how many cords it
was, and it turned out to be two interleaved lines rather than one continuous
cord. That’s a real property of the pattern, not a rendering artefact, and it’s
the sort of thing the construction method gives you for free.
Getting it onto the machine
For engraving I switched the strands to relief, which flattens the weave into
outlines the laser can follow, and exported an SVG straight from the add-on in
millimetres.
Now, an honest note. My laser runs on LaserCut 6.1, which is old software tied
to the controller in the machine, and it won’t take an SVG. So I round-trip
through Illustrator and export a DXF. Most software made this decade takes SVG
natively and you won’t have to do this — but if you’re on the same vintage of
kit I am, know that DXF export is coming to the add-on so the detour goes away.
What did survive the trip is worth pointing at: every profile is a single
closed line with one start and one end point. No stacked duplicates, which is
the usual tax on vectors that have been through three programs. The laser
doesn’t retrace anything and you don’t pay for the time.
Eight minutes on the machine.
Try it
The free edition of Celtic3d Knotwork is not a trial. It’s flat panels, borders
and crosses, both break types, weave and relief, every export format, and
commercial use — and it doesn’t expire. No card, no licence key.
Pro adds rings, cylinders and toruses and more strand profiles, £25 / $34 for
the first year across three machines.
Blender 5.2 LTS, on Windows, macOS and Linux.
