A prototype is a mock-up or rough draft of a part. Successful metal prototypes lead to better finished wall and roofing assemblies. They reduce guesswork and help architects make design changes. Even though a desired metal wall or roofing assembly’s appearance is already known from an architect’s basic concepts and designs, a tangible, working model helps ensure that metal componentry fits together seamlessly via testing its performance and limitations. This helps to detect flaws.
A successful metal prototype can lead to better finished wall and roofing assemblies
An example of a metal prototype. PHOTO COURTESY OF TUSCHALL ENGINEERING INC.
Physical prototypes of wall and roofing assemblies are much easier to interpret and test than drawings. A prototype’s “looks-like appearance” helps successfully conceptualize a final product. Fabrication processes create highly accurate representations for form studies, functional and visual validation. Via cutting, bending, forming and assembly, metal prototypes can be viewed, given a hands-on review and tested as a normal part of the design process. They can also be used for marketing, brainstorming, trade show displays or for other reasons. Prototype quantities can be as low as one or as high as several hundred. A metal prototype has important long-term cost benefits. If a metal wall or roofing component will eventually be mass produced, it is relatively easy to turn it into a metal finished product.
PROTOTYPE DEVELOPMENT
Jim Tuschall, president ofTuschall Engineering Inc., Burr Ridge, Ill., says there are three main factors to developing a metal wall or roofing prototype for an architect: appearance, performance and interfacing with other materials. “Appearance is important, so the design intent has been satisfied and is do-able. Performance usually includes water and wind testing. Interfacing relates to how other materials can transition for appearance and performance. How do the metal panels run into windows? How do they get flashed? Are the windows pushed back? Architects want to see that detail, the merging of the materials for appearance and things like how it’s kept watertight.”
An example of a metal prototype. PHOTO COURTESY OF TUSCHALL ENGINEERING INC.
An example of a metal prototype. PHOTO COURTESY OF TUSCHALL ENGINEERING INC.
Tuschall says prototypes benefit architects’ designs via color, joint location, fastener type and location. “Once the architect sees the prototype, they can modify to achieve intent.” He explains that a good, well-fabricated prototype consists of accuracy and, “Incorporating all related materials from metal panels, furring, insulation, windows, doors, edge conditions, brick, etc. The component system needs to be as complete as possible. The architect wants to make sure he’s satisfied with his design attempt, and he has to answer to the owner. He’ll ask the owner about his opinion on the prototype’s appearance.”
Mike Wallace, president of Rogers, Minn.-based Americlad LLC believes the architectural community will typically design a product or profile with the assumption that it can be built as drawn. “It’s not uncommon as most architects are not as well versed with what might or might not be achieved with sheet metal products. This is where a reliable manufacturer, fabricator or sheet metal specialist can be instrumental. Oftentimes, we find ourselves in a position where the design is questionable as to whether it can be built. It might be specified as a composite product or a steel profile that might limit the odds of achieving a good result. Regardless, the architect needs to be open with potentially changing the product to a more suitable metal substrate. The goal is to get as close to the design as possible.”
Wallace explains that this example is typically a situation where a small prototype might be considered; the architect will be assured that the end result is acceptable. It also gives the manufacturer the opportunity to prove themselves to the designer.
“Going through this process of building the prototype often can result in finding minor tweaks to the manufacturing process. This could mean special tooling or having to use other sheet metal techniques such as welding and grinding, back routing, or even using a polyurethane die to achieve the results. From the manufacturer’s point of view, it gives them a good understanding of what it takes to build the product from a labor perspective.”
An example of a metal prototype. PHOTO COURTESY OF AMERICLAD LLC.
An example of a metal prototype. PHOTO COURTESY OF AMERICLAD LLC.
Jeff Barnard, CSI, CDT, architectural sales representative, Englert Inc., Perth Amboy, N.J., explains, “Prototypes are important to an architect who needs to be assured that a panel system meets the building code and will not fail. Prototypes are generally designed once code officials change the code requirements. For example, after Hurricane Andrew, the code wind speed numbers were increased, as Andrew demonstrated the previous code was inadequate.”
PROTOTYPE TESTING
Prototype testing is essential. It validates design decisions and evaluates wall and roofing assemblies to guarantee exacting specifications before development starts. An initial fit test of metal within an assembly at the prototype stage can show errors such as gaps, overlaps, misalignments and other assembly issues. Functional prototype tests examine parameters such as strength, stress, impact, performance, reliability and anything else critical to the design. Other prototype tests can include functionality, appearance, engineering requirements and even interfacing with other components. Testing prototypes reduces material waste, labor and costs.
Metal roofing manufacturers prepare full-scale prototypes of metal roofing assemblies, which are tested to determine the wind uplift strength of the panel system.“It is necessary to perform mock-up tests or simulations because a standing seam metal roof system has hidden clips that conceal the fasteners that attach the roof to the building structure,” Barnard says. “Because the panel clips themselves have to be strong enough to resist the forces that develop, and the panel clip-to-panel connections have to be strong enough to resist the same forces, and the panel-to-panel connections also have to resist the wind uplift forces, this creates a number of variables. [There are] too many variables for an engineer to evaluate using mathematical methods. So full-scale [prototype] tests have been devised which determine the strength of the panel system, so engineers can determine with confidence whether or not a metal roof or wall panel system will be torn off of the building.”
PHOTO COURTESY OF AMERICLAD LLC.
Barnard cites the following as common metal prototype tests:
UL 580 Windload Testing of Light Gauge Roofing: This test involves a 10- by 10-foot assembly of panels installed over steel purlins. The assembly is mounted in a specifically designed chamber which creates both positive and negative wind loads on the panel system.
UL 1897: UL 1897 is the same test procedure as UL 580 however the panel assembly is tested to failure. UL 1897 is often used to establish the strength of a panel system for a subsequent FBC Product Approval and possibly a Miami/Dade NOA.
ASTM E1592 Standard Test Method for Structural Performance of Sheet Metal Roof and Siding Systems by Uniform Static Air Pressure Difference: Test method originally developed in conjunction with the Army Corps of Engineers which tests a panel system to failure at multiple spans.
FM Class 4471: Test beds are typically 12 feet wide by 24 feet long and include 16-gauge Z-purlins spaced 5 feet off-center. The test assembly simulates wind uplift pressure on the panel system, and measures the pressure at failure. Barnard adds the standards for prototype fabrication are established by the testing agencies (UL, ASTM , FM), and are checked by the testing lab
Wind testing a prototype. PHOTO COURTESY OF TUSCHALL ENGINEERING INC.