As we developed our precast panel surface geometry, we found ourselves increasingly pushing the limits of our rendering engines. We knew that natural light could potentially reveal different effects on the complex surfaces, and physical models would be the only trustworthy method of study to ensure a more predictable final product. For ease of fabrication, the initial scale of these physical explorations was at 1/2″ = 1′-0″, and we determined that the most complex corner condition would be the most pertinent segment of the building to study.
Our 3D printer played an integral role in these physical studies. The printer’s high resolution allowed us to approximate the textural intricacies we were developing in Grasshopper, and we were able to almost immediately evaluate the design developments in natural light. Shortly into this process we discovered that the main shortcoming of the printed product was its very subtle translucency. This optical discrepancy was enough to force us to look towards other materials for our model production. We quickly devised a method (based on one of Steve’s previous experiences) to rapidly duplicate a single master-print panel using Hydrostone. From a master panel we created a silicone negative mold. These silicone negatives would be the formwork for our 200+ panels required for the 1/2″ model.
As we were building and refining the 1/2″ model, we were simultaneously developing larger panel models at a scale of 1″ = 1′-0″ to help us more accurately determine the ideal depth of the surface texture. Our goal was to decrease the textural depth to the minimum required to generate a desired visual contrast. These iterations were then photographed in a series of controlled lighting conditions. Based on an empirical photographic analysis we determined that a 1-1/2″ textural depth was optimal. This not only reduced the protrusion of the panel surface from the face of the building, but it represented a 4.5% material savings over our original 2″ depth.
Constructing the physical models was immensely educational for our in-house design team. The process gave us insight into some of the tectonic issues that the actual builders would face in the field. We became aware of the importance of the panel-erection sequence, a variable which the design-assist team later found to be absolutely crucial to achieving adequate construction tolerances on the building itself. Moreover, the model proved to our in-house design team that the subtlety of the surface texture would indeed produce some widely varying and exciting visual effects that complemented the project’s larger design goals. After building the model, the team possessed full confidence that the results of an almost completely digital design process would be well worth the risks of execution.
The physical model also proved invaluable in discussions with the rest of the design team. The 1/2″ scale hydrostone panels were often used in meetings reviewing formal refinement for the casting and form-liner fabrication process. Architectural Polymers, our form-liner fabricators, used the same Rhino file that was used to create the 3d prints for the model. A large CNC router was used to cut the full-size master from a piece of high-density foam. As we mentioned in the post on the panel geometry, all of the panels sizes are derived from the largest panel. This allowed a single master-panel to be used as the primary casting surface for every panel type.
Panels smaller than 8′ in height were cast from the master by building a dam across a flat portion of the valley defining each rib. Through the collaborative optimization of the surface geometry, a 3/8″ wide surface was determined to be the minimum possible dimension to create an effective seal with the dam. In contrast, a sharp valley condition would have produced a peak in the rubber form-liner which would have been susceptible to wear during the repetitive form-liner casting process. Durability is greatly enhanced in this optimized geometric configuration.
Dimensional differences between the four corners of the building would have potentially required as many as 16 additional foam masters. Close collaboration with the form-liner and precast fabricators reduce the number of corner masters to three by decreasing intersection tolerances. The above image shows the unique ‘legs’ in color and standard ‘legs’ in grey. The optimization of these corner conditions to reduce formal anomalies represented a significant cost savings to the precast fabricator, as CNC milling time was the main driver of the base form-liner cost.
The design-assist team has recently completed a full-scale performance prototype at Construction Research Laboratories outside of Miami, FL. Construction of the prototype allowed each of the trades that will be working on-site to better understand the overlap between their responsibilities, refine erection sequencing, and have a few cold beers in the hot Florida sun. It was also a chance for our design team to see a portion of the building come together at full scale, and realize just how valuable the physical modeling process was in refining the tectonics and componentry. Testing of the prototype should begin next week, and is to include pressurization, infiltration, and seismic tests (sadly the famous projectile test is not required for buildings in Cleveland). We’ll post more about the results and some of our lessons learned when testing is complete.