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RWDI prints architectural models in a quarter of the time using industrial stereolithography
For five decades, RWDI has delivered wind tunnel testing and environmental services for the world’s tallest buildings, including the Burj Khalifa. Almost every skyscraper in London’s square mile, and the world’s most architecturally-ambitious sports stadiums, have, quite literally, been shaped by the work of RWDI’s model makers, structural engineers, scientists, and wind engineers.
Ground-breaking research
RWDI was originally founded by multi-disciplinary team, Bill Rowan, Colin Williams, Anton Davies, and Peter Irwin to analyse the structural impact of snow loading on Canadian buildings. The company devised industry-leading tests, using sand and water flows to model how snow would gather on building surfaces, to ensure that architectural designs complied with Canadian building regulations. This work evolved into the wind engineering tests and analysis provided to architectural firms around the globe today.
Before breaking ground, tall buildings must be tested for their wind resistance to ensure safe structural loading, analyse downdraft, and understand pedestrian comfort. Wind consultants’ recommendations help architects to deliver cost-effective, efficient designs that demonstrate consideration of all impacts.
To achieve a realistic interpretation of how a structure will stand up to various wind speeds, and how surrounding buildings will channel the wind around a planned construction, RWDI creates detailed scale models from the architectural drawings and analyses the structures in specially-designed wind tunnels at its sites in Canada, India and the UK.
Moving with the times
Traditionally, all scale models were built by hand by RWDI’s model makers.
When industrial 3D printers emerged twenty years ago, the team at RWDI HQ in Ontario, Canada began to supplement this hand-built approach with 3D-printed models. Using fused deposition modelling (FDM) enabled the company to create, instrument, and test architectural models weeks sooner.
As a company that has always led the field, RWDI Canada was also an early adopter of 3D printing using large stereolithography (SLA) machines, which often use proprietary resins.
Ryan Keen, a digital modelling specialist who works at RWDI’s UK office in Milton Keynes, comments, “Clients always need wind engineering reports delivered as soon as possible and we’ve got to try to meet those targets. RWDI invested in SLA machines in Canada and shaved weeks off the modelmaking schedules. However, the proprietary resins are very expensive.”
“In the UK, we’ve invested in industrial FDM printers over the years. They still save time and are a fraction of the cost of stereolithography, but because FDM printing involves polymers being printed in successive layers to create the 3D structure, this leaves layer lines, which can reduce the level of detail on the model,” Ryan observes.
iSLA Clear Resin model of The Shard
Bringing SLA models within reach
As market adoption of industrial 3D printing has increased, the cost of machines has become more competitive. This created an opportunity for RWDI UK to take a fresh look at industrial SLA printers.
Ryan Keen turned to industrial 3D printing specialists, CDG 3D TECH. For more than 25 years, CDG 3D TECH has provided 3D printing consultancy, machine installation, field service engineers, software training, materials specialists, and supplied industrial 3D printers to the manufacturing industry.
As an independent supplier of 3D printing products and services, CDG 3D TECH works with major 3D printer manufacturers and introduced RWDI to the ZRapid, iSLA660 printer, which uses open-source resins.
“Open-source resins are a fraction of the cost of proprietary resins,” enthuses Ryan Keen. “This opened up the possibility for us to consider investing in SLA printing in the UK.”
Supporting innovation with SLA
As a leader in the development of wind engineering tests, RWDI is continually improving its testing processes.
“One of the things that RWDI can do is to print instrumentation within the models, where we’re looking at the facades of the building and measuring pressures placed upon on it. This involves growing air tubes into the 3D printed model,” explains Ryan.
Traditionally, air tubes would be manually installed into a model and linked to RWDI’s pressure-measurement equipment. For a complex building, the addition of these air tubes could require weeks of painstaking work by the modelmakers.
“Working digitally, we’re doing the instrumentation part up front and then printing the model. However, with FDM printers, we weren’t able to do that because the material is more porous. When air is forced through, even if you got a pressure measurement, it probably wouldn’t be accurate, because the model loses pressure. SLA printing eliminates that problem,” explains Ryan.
Put to the test
RWDI’s UK team undertook extensive testing of the ZRapid iSLA660 over a period of several months before investing.
“I was primarily looking for four things: quality, speed, cost, and whether the printer could produce the level of printed instrumentation that we need for our models,” reports Ryan Keen.
“We came to the conclusion that SLA was the best way for us to achieve these four goals. CDG 3D TECH found us a machine that met our budget, while also being large enough to handle the volume of work that we want to put through it. Having a slightly bigger volume allows us to produce more models, and it’s quick.”
As a result of CDG 3D TECH’s partnerships with Anima, ZRapid and PostProcess, the latter supplying a Demi 830 for cleaning the SLA resin models, RWDI was provided with a complete solution encompassing the industrial SLA 3D printer, open-source resins, washing, curing, finishing, training, and support.
“CDG have always supported us in the way we like to test things and provide the machines that meet our needs,” Ryan attests. “As part of the package, they came in to install the machine, then provided us with training on the software and how to clean up models in postprocessing to remove excess resin. Very quickly, we were trained, and then up and running.”
Fit for Purpose
RWDI continues to combine hand-built model making with FDM and SLA printing, depending on the project’s test requirements.
“We still use our FDM 3D printers where testing of the design’s structure demands different requirements, based on its characteristics and material properties. For other study types, it makes more sense to leverage SLA.” explains Ryan.
Clear Results
Ryan Keen jokes that the extensive use of red FDM filament for 3D printing has resulted in the RWDI UK team’s work being recognizable by its signature red models of iconic London buildings such as 22 Bishopsgate.
“In Canada we have always had a requirement for clear resin because it enables us to see the instrumentation inside the structure. And also, clients really like translucent models,” he comments.
The introduction of the ZRapid, iSLA660 printer has allowed the UK team to directly compare the SLA and FDM printing times, with SLA being proven to be around four times faster.
“We’ve seen significant time savings since investing in SLA,” reports Ryan. “We grew the exact same model using FDM and it took 193 hours, while SLA took 48 hours. That means we can get that product into the model shop to instrument it for the wind tunnel almost a week quicker.”
Whether printing translucent architectural models, or comparing the times taken to grow models. The SLA results are clear, especially in terms of material properties and time saving.
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