I had to think about the “kerf” of the laser. Just like a saw blade, the laser wastes some material as it cuts, and if I didn’t allow for it there would be a gap between the pieces of wood. Also, it’s not possible to make a perfectly sharp concave point in the edge of some wood, there needs to be a certain radius to allow for the width of the laser. On the other hand it’s important not to round off corners where multiple pieces meet otherwise there would be a gap.
I did a test by getting nine rectangles cut; this showed that the laser kerf is between 0.18 mm and 0.25 mm at its narrowest, and is slightly V-shaped, up to 0.35 mm. I chose to use the smallest value, 0.18 mm, for the kerf.
So there was some work in rounding off sharp points where necessary. Then I transferred the design to AutoCAD and used it to trace the polygons, which I then grew by a small amount to allow for the laser kerf – you can see the light wood and dark wood polygons in yellow and red overlapping slightly:
Some of the rectangles of the same colour now overlap, so I spaced them apart vertically (along the grain of the wood) – I made the gap 5 mm so that the cut sheet of veneer would have some strength, being a sheet with holes in it, rather than being cut to ribbons:
I got the veneer cut by Cut Laser Cut in London. The veneer comes out looking quite burnt on the rear side, but beautifully clean on the front (especially as they protected it with some tape before they cut it):
Some of the tiny pieces fell out when they cut the veneer and they very conscienciously edited my drawing to cut some replacement tiny pieces out of the scrap veneer, which they put in a little bag!
For the plaque I cut a piece of 19 mm plywood and glued the veneer edges on, before trimming them off with a router. I also recessed a “keyhole” hanger into the back of the wood.
There were lots of fiddly bits of wood to piece together; I used masking tape to hold it all together and then glued the veneer to the front of the plywood using hot-melt glue sheet heated with a domestic iron.
The panel needed harldy any sanding. When I went to the very finest abrasive (1600 grit), the grain in the lighter wood suddenly became much more distinct.
The final stage was to spray wih 4 coats of arylic laquer.
I’m really pleased with the result.