I wanted to put Autodesk Fusion360‘s Simulation feature to work. I decided to create a block that supports the three legs of a stool and ran the space optimization study over it. Using a plastic like ABS in the simulation and MDF for the legs, I could get an estimate of the stress-contours (best among woods and plastics). I used these as templates to remove excess material and decided to 3D print a piece, a slide in joint/frame for my seat.
Now this is the step which is not the right way to go about testing a part for strength – since plastic has a non-linear Young’s modulus and 3D printed parts are neither really solid nor with uniformity among the layers, FDM is definitely not the way to obtain a test piece (however SLA printed parts fare better in this). But I did it anyway, to see how much this shape could take with a ten percent infill just with the defining walls on the outside making up this part – would anyway be a good indicator.
Surprisingly, everything fit well and the seat was able to take my weight, but because of the lack of joinery, it would wobble and slide out of the fixtures with any movement. So, as a way to keep this piece serving some purpose, I just applied some wood glue to the dowels and jammed them between the legs and the top.
For future, this frame could incorporate a clever locking mechanism for the legs and maybe have a smoother, more organic surface without the very much visible fillets.