Egypt The model for Metis’s Great Egyptian Museum project was the most challenging and in many ways the most engaging. Metis’s starting point for their proposal was the renowned measurement of the pyramids in carried out in 1881 by the archaeologist Flinders Petrie, a survey carried out through a triangulation of projected lines. Metis took a representation of the geometrical lines from the site of the survey and folded and refolded them onto the proposed site of the museum. The brief for the museum required a series of galleries and archives to house the Egyptian national collection of antiquities. Metis proposed that the galleries take the form of five large ‘vessels’, grouping the collection into curated themes of culture, scribes and knowledge; religion; man, society and work; kingship and state; and the land of Egypt. Each vessel had a unique and complex geometry but was also understood as being part of a coherent whole. The material proposed for the actual construction of the vessels was weathering steel and it was important that the set be closely linked by their common materiality,. These vessels would be interlinked by a series of bridges allowing visitors to create their own itinerary. The vessels were raised above the ground, creating a constructed landscape of shaded, interconnected folded planes. As part of their competition entry, Metis had constructed a card model. The model showed a sectional cut through the ground, folded landscape and the five vessels, revealing floor plans and points of connection. The new model required for the exhibition used a palette of materials. The ground was represented by solid hardwood with the folded landscape above made from planes of plywood. The structures holding the vessels above the ground, the internal floors and the bridging elements would be 3D-printed. A dark and very dense tropical hardwood was chosen for the vessels to impart a heavy, monolithic feeling, with intricately embellished surfaces. The choice of material (in both cases, model and proposed building) signified a crisply folded precise wrapping and protective securing of a more delicate interior. The process for making the new model began by digitally tracing hand-drawn plans and taking references from the card model. This information was aggregated in a digital model, with elements coded by colour, in layers and in groups, resulting in a dense set of digital material (see the drawings to the left). Rather than one illegible stack, several iterations and selected model parts are arrayed in the virtual space. The distances between the parts are not arbitrary but located at specific distances, allowing multiple virtual iterations to be moved back and forward in connection to other virtual material. Sections that would be laser cut could be worked on independently and then checked back against sections that would be CNC-routed
or 3D-printed. As well as modelling in three dimensions, two-dimensional nets mapping the facades of the vessels were digitally unfolded, rotated and categorised in isolation. The typical materials used for CNC routing are flat, uniform and have a consistent density – typically MDF, plywood or modelling foam. Standard techniques include a ‘safe margin’ around the area to be cut. The wood selected for the base of the Egypt model had an irregular form but was relatively straightforward to machine. When preparing to CNC rout this piece it was necessary to establish a way to reference the digital model to the physical. This did not require a faithful modelling of the exact physical dimensions of the wood in virtual space, but only the more significant points of calibration. The tool paths that were generated were designed to extend beyond the material present to ensure the desired areas were fully machined. Routing hardwood to create the vessels proved more challenging. The hardwood selected had been salvaged from a furniture workshop that was no longer operating – it was not possible to find any more material that matched the density, colour and texture. The dimensions of the block would accommodate the cutting of the five vessels. The geometries of the vessels were outside the standard limits of the CNC equipment. On the first attempt a failure resulted from using the automated software supplied with the CNC. The software script instructed the cutting tool to travel directly from one cutting stage to the next. As a result, unable to lift the cutter high enough (because the wood was outside of standard limits), the tool travelled through the block damaging the piece. The clash was spotted quickly and the damage limited, luckily there was enough material left in the remaining volume to machine all five blocks. The CNC automated programme was no longer a possibility, but it was possible to rewrite the scriped movements. The solution was to digitally draw vector paths for the cutting tool that would ensure the cutter would never need to lift whilst in the work-piece. The tool would approach the work-piece at the appropriate depth and would cut a trench along a predefined path without rising from that path until outside the hardwood. The machining could also be paused to allow the tool to be extended further when appropriate. Writing the tool paths involved drawing two-dimensional pathways on drafting software, establishing different depths with colour coding, and calculating effective offsets for each line based on the radius of the cutting tool. When each of the pathways had been drawn, the combined drawings were output1ed as g-code.14 After the experience of the first failure, the cutting pathways were first tested with a low density, low-cost foam. The foam was used to highlight any miscalculations or unforeseen errors. After this
The Great Egyptian Museum project: from top: Folded web, vessels and hyperlinks Card model by Metis (left). Routed ground condition in spalted beech Testing tool paths in low density foam Unexpected clash between routing tools and material all images: richard collins
On Site review 35 : the material culture of architecture
19
Made with FlippingBook interactive PDF creator