Structure/Surface
From the outset we instinctively felt that such a form would require a radical rethinking of the extant logics of fabrication, which typically separate out the functional elements in a building (structure separated from surface, waterproofing separated from insulation, etc). To fabricate such a form by combination of elements by different contractors/suppliers seemed untenable in its complexity. Clearly we needed to collapse such multiplicity into singularity, and move to the high accuracy and dexterity of numeric command fabrication.

Our strategy has effectively been to imagine a multi-functional skin that would itself perform structurally and environmentally, and which would be directly machined as a singular fabrication process. We have given principle consideration to composite honeycomb panelling, either in fibreglass or aluminium, which may be filled with dense resin to machine locally, and filled with insulation more generally. These panels are potentially very large, lightweight, and highly performative, able to act as the structure, and they can be machined easily. Their high material cost (reflecting their complex manufacturing process) will be more than offset by the collapse of fabrication time and the simplicity of a singular CAD/CAM process.

CNC Machining / Assembly
The issue in machining a series of flat panels is to be able to cheaply cut flat swathes at the bevelled edges, rather than using a drill-head. Eurocomposites have developed flat propellor-like cutting discs for high-speed planar cutting of their resin-filled aluminium honeycombs, and we deployed their expertise in the creation of the first prototypes. Our CAD files give the accurate 3d form of every triangular panel, which is simply machined using a large 5-axis CNC machine.

We have articulated the project into a series of topologically-variable boxes, six-sided triangular sleeves with a triangular top and bottom: this gave Arup a basic ‘module’ which, when given an internal stiffening plane, offered two pyramids. This form is structurally determinate, allowing engineering assumptions to then be made with fair certainty.

The triangles are machined then bolted together to create the box elements, which will then be bolted together to form box trusses. All the bolt-holes and glass grooves, etc, are accurately machined into the individual panels such that they are easy to assemble in 3d. The project comprises 11 large structure/surface elements whose size is defined by the maximum size of a truck: preassembled in the factory, they are simply transported to site for lifting and bolting together.

Prototypes
We have created prototypes in both aluminium honeycomb and fibreglass honeycomb, each offering certain advantages (cost versus performance). Ove Arup engineers were at first doubtful in the need for such tight manufacturing tolerance in complex 3d assemblies, but they have been impressed by the millimetre-perfect fabrication as by the stabilty of such materials under climatic variation. We will now generate a series of full-scale prototypes that can be tested structurally and environmentally. The goal is to give confidence as to the ease of fabrication that such new processes allow, and to then bid the project. Current estimates suggest that the fabrication efficiency (the collapse of contractor space) will allow such forms to be realized within standard budgets. This announces that the bottom drops out of standardization as the real import of digital technologies makes itself felt.

Of interest to Ove Arup was the weight of material that comprises the structure (which they assume is a 3mm thick external aluminium skin: this suggests that the actual use of material in such a project is highly efficient, most particularly when the form can be varied to optimize the structural configuration. One then dreams of recovering efficiency in both manufacturing logic and material deployment in space, yet within the context of an extraordinary formal liberation as architects are able to move fully into 3d articulacy.