Digitally Fabricated House for New OrleansLawrence Sass Massachusetts Institute of Technology
Figure 1 MoMA opening July 2008, and entrance to the Digitally Fabricated House for New Orleans
The Digitally Fabricated House for New Orleans was an exhibit building designed and built by Prof. Lawrence Sass of the Massachusetts Institute of Technology (Figure 1). The structure was commissioned by the Museum of Modern Art (MoMA) in New York City, along with four other full-scale structures, to serve as part of a larger exhibit entitled Home Delivery: Fabricating the Modern Dwelling , curated by Barry Bergdoll, in the summer of 2008. The project was also designed and supervised by MIT researchers Daniel Smithwick and Dennis Michaud, with assistance from MIT students Laura Rushfeldt and Lara Davis. The project's purpose was to illustrate the potential of mass-customized housing when digital fabrication is used to produce wood-framed homes. The structure was an assembly from over 7,000 CNC-cut, interlocking parts. Component assembly was sustained by friction without need for nails or screws.. The project’s novelty was based on successful application of a new building system defined here as Planar Construction (a method of physical construction from interlocking flat components). The exterior dimensions were 16'-4" (5m) wide by 38'-2' (11.6m) feet long and 20' (6 m) in height; interior dimensions were 15' (4.5m) wide by 25' (7.6m) long by 18' (5.4m) in height. Planar construction is a low-energy delivery system delivered by flatbed trucking as packaged components. This system is an alternative to conventional prefabricated home delivery by specialty trucking where a modules or large panels are set onto a foundation by the use of cranes. Planar structures do not require cranes or heavy scaffolding. The novel system also lowers costs by eliminating redundant tasks on the part of the builder, such as calculating and measuring with tape measures and manual cutting of wooden parts with hand held tools. These two tasks are not limited to onsite construction, as they are also tasks performed in prefabricated housing factories. Alternatively, all components in this project, from the internal structure to operable doors, windows and finished wood flooring, were fabricated offsite in Exmore VA, by Bill Young of Shopbot Tools Inc and at MIT in Cambridge, MA, using computer-controlled machines.
Figure 2 The Instant Cabin (2005)
In 2005 at MIT, The Instant Cabin was a digitally fabricated, all plywood interlocking wood structure, also directed by Professor Sass. One hundred sheets of plywood were used to fabricate one thousand interlocking elements with a single CNC machine  (Figure 2). The cabin was designed, fabricated and assembled as a four-step process (Figure 3). Once the initial 3D model (design) was created in the computer, a collection of smaller interlocking planar elements was generated guided by a set of fabrication rules (1). Composition of the elements, location in space, integral assembly geometry, size limits and element shapes were constrained to the limits of average plywood sheet stock (48" x 96" [122cm x 244c]) (2). Each element was modeled as a 3D shape inclusive of friction-based assembly features and a number that was used later to guide manual assembly onsite (3). Last, a worker assembled the manufactured elements using only a rubber mallet. Assembly was sustained by friction only (4). There were three core lessons learned from the Instant Cabin carried over to the Digitally Fabricated House for New Orleans
● Assembly-only construction, all components are fabricated with adjoining attachment features
● Numbered component assembly and low use of power tools in construction
● Every component can vary in shape, function and size
● Component checking by laser cutting a scaled model prior to full-scale fabrication
Figure 3 Four stage concept
Exhibit Function and Prototyping
Entry to the building was through one of two staircases, as opposed to the typical single flight found in common shotgun houses, to improve circulation of visitors in a high-volume exhibition setting. Inside there was a scaled model built of laser cut components created from the same data used to build the full-scale construct (Figure 4). The central model was 1/6th the size of the full-scale construction, and it was used to detect errors in the CAD modeling before final cutting at full scale. The model included every component found in the full-scale version of the structure complete with interlocking features.
Figure 4 Exhibit strucutre interior with scale error detection, error correction model 1/6th full scale
Planar Construction is ongoing research exploring digital manufacturing directly from CAD models . It is not a commercial product or software. It is a manual process of CAD modeling and drafting best defined as a generative system that creates structures of all shapes and sizes as a composition of small interlocking parts . Production starts with a 3D shape model and ends with data used to manufacture components with any 2.5D computer controlled cutting device. It can be used as internal or main body structuring for large products such as houses, windmills, and cylindrical structures such as drones and watercraft . Advantages of Planar Construction are similar to benefits found in additive manufacturing. Benefits range from low waste to scalable and on-demand manufacturing of large artifacts. Most important for building construction is that component assembly requires only a few handheld tools. There is no manual onsite cutting of parts. This construction system is flexible enough to support mass-customization and instant fabrication of any product larger than one meter square. Last, the system is a non-centralized method of production, meaning that the designer and builder can be in separate geographical locations.
Figure 5 3D Print of a design scheme for the facade
Design and physical delivery of the structure required broad application of CAD-based software and computer-controlled machines. Starting with the shape model, highly detailed desktop models were produced for evaluation using 3D print machines (Figure 5). Next, a laser-cut, larger size desktop model was constructed from the similar 3D CAD model used for 3D printing. Building elements for the desktop model were generated as 2D elements using the same interlocking methods applied to the Instant Cabin. In both the cabin and this house, modeling the structural body was generated from an internal lattice and an external surface (Figure 6). The larger scale model, manufactured from 117 Masonite sheets with a common laser cutter, was used to test the shape and assembly of each element as a physical interlocking part. Afterwards, the laser cut model was treated as a base for attachment of ornamentation of a thinner stock of sheet goods. We discovered many errors in CAD modeling after laser-cutting parts, illustrating the limitation and cognitive overloading associated with manual modeling. A second desktop laser cut model was also fabricated and later used in the exhibit. Larger, full-scale mockups were built as sectional models to test alternative materials such as OSB for weathering.
Figure 6 Starting model, Interior contours and exterior sheathing
One great advantage of working with a precise system is that groups of parts can be considered modules. The framing is considered as one module, trim, doors, windows and flooring are all considered modules composed of many parts (Figure 7).
Figure 7 Modules
Once approved, the same data used to construct the desktop model was emailed to fabricators in Virginia for full-scale CNC manufacturing. A total of 1,163 components were fabricated from 578 sheets of 3/4" and 5,401 components cut from 95 sheets of 1/2" plywood. The process was mostly error free. Of the 6,564 components, only two components were found to contain errors.
Components were delivered from Virginia to NYC, packed within their original plywood sheets. Bundles of plywood (45/bundle) and components within each sheet were organized based on assembly order. The first parts to be assembled at the base of the building were packed into the first bundle of plywood; ornamentation and flooring was packed into the last bundle. The base structure (grey parts) was assembled in 18 days and the white ornamentation components were assembled in 5 days. The structure was screwed to a concrete foundation. The entire project was assembled onsite by four people over the course of 23 days. Major tools consisted of mallets for hammering panels, clamps to hold assembled panels in place, and crowbars to align parts. Miscellaneous tools included hand held routers used to release tools parts held by tabs in the original plywood sheets (Figure 8).
Figure 9 Final Assembly in NYC
A major limitation of this method of constructing a building was that CAD modelers experienced an overload of design tasks and responsibilities. All data entry was manual through the keyboard and mouse.
Modelers were responsible for management of structural integrity, design of every component within the structure, and component logistics. Modelers could benefit from automation of CAD functions.
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