Computer Controlled Machining

This week is about computer controlled machining, and making something big!


I decided to try to make a small version (something that would fit on 4x8ft of plywood) of this chair.

Chair design

I designed the chair so that it could be cut in a 2D plane using only two tools (1/2" and 3/8"). We set up the job to leave an onion skin after the first cut to be sure that the large bendy pieces would stay flat on the vacuum table.

.....unfortunately, as I learned, plywood is pretty crappy quality, and the poor glue between layers (and in some places complete lack of a middle layer), caused the back of the chair to vibrate out of place.


So, next I tried recutting just the back piece in 3/4" veneer which gave a beautiful result and still came out very flexible.


I had a friend help me put together the chair, the wood is a nice material to work with, we were able to flex/bend/stretch/compress it quite a bit without cracks.

...Now it looked nice, but with any weight on it the plywood started bending heavily, so I added cross-strings to keep in place, which helped tremendously.


I still need to replace the zip-ties with a nice leather string for holding the surface down, and I would like to redo the sides in 1/2" veneer instead. Finally, though comfy, the center of mass of the rocking chair is currently too far forward to make it really comfortable, so I might fix that too: good news is that the surface can be reused!

Chair Update: A ouple of days later, my unfortunate labmate sat in the chair and broke the sides. The cheap plywood definitely didn't do it's job. So three weeks later I finally had time to buy nice 1/2" birch plywood and redo the sides of the chair. (And while I was at it, I made an ottoman, and a table too). Super happy with the new design!! :)
Also, I got the cutting values for the Onsrud much better this time, so no extra sanding of the ottoman surface was needed.

Here's the final files I cut: Chair surface came from this file. (I recommend lowering the feed rate quite a bit to avoid splinters). Chair, foot rest and table here.

...Also, I removed the zip-ties and added nice leather coord instead: