Morphosis Prints Models
The 3D printer spreads one thin layer of powder over the print bed, then passes over the powder just as an inkjet printer head passes over paper. Where the digital model indicates a solid, the printer, using a modified inkjet printer cartridge, injects the binder cyanoacrylate.
After one pass, the print bed lowers by one thickness of powder, and the printer spreads another layer of powder and jets another pass of binder. The cycle continues until the top layer of the model has been printed. This process takes about five hours for a 6- by 6- by 6-inch (15- by 15- by 15-centimeter-) model. The actual time depends on the solid volume of the physical model.
When the printing is completed, a 6-inch- (15-centimeter-) tall model is immersed 6 inches (15-centimeters) deep in powder. Raising the print bed, you remove the "part" and vacuum-clean out the excess powder, which can be sifted and reused.
Morphosis has adopted the practice of baking the newly "printed" model in a small oven for about an hour at 200 degrees Fahrenheit (93 degrees Centigrade) to finish its curing. If parts are still fragile after baking, we manually apply a coating of epoxy or cyanoacrylate to stiffen them.
After printing, about 20 percent of our models need touching up. But only 5 percent are unusable, so we consider our success rate to be high. The firm's designers have learned to anticipate the needs of the physical model, making, for instance, pieces no thinner than 1/10 inch (2.5 millimeters).
The process of finishing a 3D-printed model varies according to one's stylistic preference. Morphosis' plaster models are typically primed with a few coats of gray spray epoxy paint and finished with one coat of spray epoxy. We have also experimented with gilding with silver leaf, and plating in copper and nickel baths, then oxidizing the finish to achieve a rich patina.
How the Model Is Used
We commonly use 3D-printed models for site studies. Morphosis prints context models at a scale of 1:200, and leaves a hole in the model base where the building would be. These site models are sent around the globe to our clients and design team partners.
As design progresses and multiple schemes are developed in parallel, scale building models are "printed" and sent to the remote locations. The recipients can insert the new designs into the hole in the base model to study the design variation in context. Because these models can be printed relatively quickly, it is practical to provide weekly updates.
Morphosis often "prints" many variants of a parametric model, with slight differences, to study design changes. Being able to see two versions side by side is sometimes more informative than viewing two renderings. It enables us to examine spatial detail at eye level.
We also make larger-scale "exploded" or diagrammatic models. Now that we develop more information within the CAD model, finer granularity of the physical model is feasible. We sometimes "print" parts of buildings at 1:50, so we can view them both assembled, to study the exterior, and pulled apart, to study the interior spaces.
We also produce structural details to study in collaboration with engineers, detailers, and contractors. Steel detailers using Tekla Xsteel software can give us their digital models, which we can import into CAD and prepare for 3D printing. These models help us reach a consensus that would be more difficult to achieve from drawings.
Evolution of the CAD Model
One benefit of developing designs in CAD for in-house model fabrication has been that the Morphosis designers have necessarily improved the accuracy of their CAD modeling. And because they spend less time building physical models, they can spend more time on design thinking.
These models have become the primary medium for studying the building's geometry, while drawings have become secondary. Morphosis is increasingly working in direct collaboration with building component fabricators — for structural and miscellaneous steel and for interior and exterior cladding. We are exploring ways to further develop the same digital models to extract more detailed information, such as steel centerlines and cladding panel sizes and configurations.
We're learning that design models need to be adaptable to various output methods. What works as input for a 3D-printed 1:100 scale model does not work for a full-scale steel plasma cutter. We plan to take advantage of the 3D printer's mold-printing capabilities, to make it more efficient to cast metal parts.
Just as we apply methods to analyze our CAD models for structure, energy, and lighting, we also want to analyze material properties. Digital analysis of curvature and thickness needs to be available to the designer in near-real time.
As the collaborative relationship between design team and detailer/fabricator evolves, we also need to learn to transfer the knowledge gained from one project to the next. It is imperative that we have tools that enhance the designer's ability not only to conceive complex forms, but also to think intelligently about how the final product is made.
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Martin Doscher is the IT/CAD manager at Morphosis. His primary focus is the integration of the virtual building model into design and construction processes.