Assignment #16
Wildcard - wood bending

For the wildcard assignment, we have to try an unfamiliar process involving digital fabrication. At the time of writing, the pandemic has closed the labs, so I came up with an idea I could make almost entirely in my kitchen.

Design of a loop object

First, I designed an eye-shaped loop made of four components: two curved wooden strips and two wooden rectangles that hold the structure together. I modelled it in FreeCAD using basic Sketch and Pad functions in the Part Design workbench.

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Steam bending wood

The wooden rectangles are easy to make, but the curved strips are more challenging. I’ll use steam to bend the wood into the shape I designed. First, I’ll 3D-print a bending form, then soften the wooden strips in a steamer.

1 – 3D modeling of the negative.

First, I modelled a bending form for a 90° arc using sketches and pads in FreeCAD’s Part Design workbench. The form is thick enough to support the wood while it is clamped. Since I expect some springback, I made its angle 20° sharper than 90° to bring the final curve as close as possible to the intended shape. I then exported the model in STL format and printed it on my Prusa i3.

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2 – Wood bending

I used a cutter to prepare two wooden strips that would fit the printed form. The CAD model helped me calculate the strip dimensions needed for the final shape. Assignment 16 documentation image: ass17 11 I then boiled water in a steamer pot in the kitchen. A small ceramic bowl kept the wood off the steamer’s grid. I covered the pot and waited 20 minutes, then removed the wood and clamped it against the printed form.

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3 – Waiting and gluing the parts

I left the wood clamped to the printed form for four hours. I was not sure how long was necessary, so I chose to give it extra time. When I released the clamps, the wood had retained a curve. There was more springback than I had hoped, but gluing the parts together brought the structure into the intended shape. My design had become a real object!

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Source files

Here are all the source files for the Wildcard assignment:
1 - FreeCAD file of the whole shape
1 - FreeCAD file for bending form
2 - STL file for bending form