Serial sectioning is an easy way to fabricate complex form using flat cuts stacked together to imply the continuity of a surface. The technique is easy and cheap, but like lots of other things that are easy and cheap, it’s also lazy and problematic. The intense, repetitive visual order of the sections frequently overwhelms the object being fabricated. It is difficult to meet the following criteria using this technique:
- Cut sections non-uniformly (not all sections cut in a straight line)
- Amplify desirable qualities of the form using sections instead of allowing the cuts to suppress them
- Distribute ribs and spacers in non-linear arrays to assemble the sections (find an assembly technique that is constrained by the properties of the form instead of constrained by some arbitrary system, like a grid)
- Work only in sheet material so that all cuts are flat 2D profiles
We’ve been working on this problem and have arrived at a solution for some lobby furniture we are designing. The method is shown here with a bench.
Front and back views of the bench surface model. The form is conceived as a thick sheet of material, pliant in the way that thick foam can be rolled in a loose tube while retaining some of the willful resistance of that material’s stiffness. Lines embedded on the surface follow the tucks and overlaps of the tube form.
Sections are cut perpendicular to the direction of the tube. There is a “wobble zone” where the sections not only turn a corner but “shake” slightly in orientation at the end of the turn. This wobble and shake in the surface normals corresponds to the willfulness of the material idea: it is impossible to achieve turns and radii without a “recovery period” of adjustment in the form immediately before and after the turn.
Spacers are arrayed along the form so that they follow the curved trajectory of the rolled tube.
The spaces are designed so that there is a rigid lock between adjacent profiles, while allowing: 1) flat custom cuts to vary the angle between sections; 2) drift between the placement of the spaces so they can follow a curve instead of straight line.