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trial run, the hardwood was carefully secured, the cutting tool calibrated and the machining speeds set. The subsequent machining would last more than 20 hours and was processed in stages over three days, with frequent checks. The tool-paths were drawn with the inclusion of tabs, sections of cutting that were omitted and that would hold the pieces in place. They were positioned with the intention of being easy to remove, that is on straight flat sections rather than on corners. After the CNC routing process was finished the five pieces were cut free using a bandsaw and tenon saw. Once separated into individual pieces, the surfaces were smoothed using chisels and sandpaper. The next stage, which involved the laser cutter, also presented challenges. Laser cutting is typically performed on flat sheets of stock material with an orthogonally referenced starting point. Often, if a mistake occurs when cutting a design, a new piece of material will be inserted and the cut performed a second time. In contrast, for laser engraving our vessels, the laser was required to engrave precisely on multiple sides of the three-dimensional forms. The forms already embodied a considerable amount of work and any misalignment would have been clearly visible. The strategy developed involved positioning the block and sending small marking lines with very little energy so that only a small trace of burning would be left on the wooden surface. The position of the trace was observed, followed by adjustment and recalibration. This process was repeated until the correct position was found and a stronger engraving command could be sent. There was a further repetition, engraving more darkly and more deeply. Four to five repetitions were typically required before moving on to the next facet. There was a significant amount of handling, positioning, propping and securing.

The hardwood is secured for machining with clamps, screws and weights Channels are carved, cutting around the desired forms Post-machining, the block is removed but far from finished

Positioning the vessel in the laser cutter with a card jig. The vessels are manually rotated and secured by whatever means possible A close up of a vessel mid-way through laser engraving

below, from the left: Routed form and 3D printed inserts, laser-engraved surfaces and oiled finish View from ground surface towards folded ground planes and elevated vessels Eroded material and marked surfaces

all images: richard collins

On Site review 35 : the material culture of architecture

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