Portfolio / Complex Walnut Parts on the CNC

As part of the ongoing research project the “Explorations of IN” at Steven Holl Architects, we were asked to fabricate the parts for several complex models in a variety of materials. While one aim of their research was “exploring what is possible in Architecture,” for us these projects pushed the boundaries of what we thought was possible on the CNC router.

Many of the “Exploration of IN” studies seem to start with a cube intersected by shapes such as spheres, with the overlap subtracted to form the inner space. These intersections tend to produce a complex arrangement of curved and flat surfaces that seem best suited for a fabrication technique such as 3D printing. However, in order to use a wider palette of materials, we needed to find a way to produce the parts on our CNC router.

This particular version consisted of twelve parts cut from solid walnut. First, the overall object needed to be split up into parts that worked within the limitations of the material, such as the available width of pieces of walnut (as well as defects in the wood such as knots). Then, we needed to factor in the capabilities of our 3-axis CNC router (e.g. no unreachable undercuts, voids, etc) as well as the constraints of tooling (which would limit stock thickness). While the orientation of parts was chosen to avoid problems such as collisions and undercuts, nearly all parts contained difficulties such as acute edges, tight corners and steep sidewalls. Furthermore, nearly all the parts required machining from both sides (sometimes referred to as “flip milling”). This meant we needed to create bridges to the surrounding material that would hold the parts in place in order to flip over the stock and resume machining from the other side. These bridges would then need to be removed by hand in the shop to produce the finished part.

While many of the models produced for the “Exploration of IN” project are conceptual studies intended for internal use or exhibitions, Holl has now completed the Ex of IN House, a 918 sq. ft. guest house and artist residence in Rhinebeck, NY, based off this research.