I am very interested in creating designs on my desktop cnc that make perfect usage of a given material when going into the third dimension. A full 3d relief cut seams a unbelievable waste of material and time. So most of my designs rely completely on 2d operations giving the opportunity to use a laser cutter or – in some cases – even a water jet.
After releasing the first version of my "Bend Spiral Bowl" on Thingiverse I got some pretty harsh comments on how difficult the built was for some readers. So I took some time to improve my design concept and after several prototypes I came up with the idea of bending the wood like the German cabinet maker Thonet invented in the middle of the 19th century – using steam.
This wooden bowl can be done in different sizes but I show the process for a rather small version. You'll need a sheet of 6 mm beech plywood approx. 22 cm x 22 cm. As tools I used my desktop cnc, a microwave oven and a suitable bowl. To finish the bowl I used some sandpaper and hard wax oil.
The basic shape of this bowl relies on an Archimedean spiral. Many graphic tools can create a (logarithmic) spiral like you see on a snake house but not this kind. I found a script for Illustrator written by Sato Hiroyuki to create an approach of the Archimedean Spiral.
When rotating a single arm I added a circle to the outside. This guarantees that the pivot point is exactly in the center. I used a 30 degree angle of rotation resulting in 12 'arms'. It took a little time to optimize the shape so I got single lines. This was best because I planned to use separation cuts, thus the design is not set to a certain tool diameter.