3D printed dragons adorn Kew's 18th century Great Pagoda

The Great Pagoda at Kew was commissioned in 1761 during the reign of King George III. In the years following the Pagoda's unveiling, it drew crowds who came to marvel at its exotic and eye-catching details - including the painted dragons on the corners of each successive octagonal level. After only 30 years or so, the dragons are thought to have been removed to accommodate roof repairs and were never replaced. Although rumours suggest the dragons served as payment for royal gambling debts, experts believe the wood had simply rotted.

As Historic Royal Palaces (HRP) began the project to restore The Great Pagoda, it needed a way to replace the dragons. HRP required a means to create new dragons that would withstand the famously inclement English weather. 3D Systems' On Demand Manufacturing team, based in the UK, delivered the lightweight, durable dragons using a scan-to-CAD workflow featuring Geomagic software, Selective Laser Sintering (SLS) 3D printing and high-quality finishing. These technologies, combined with the expertise 3D Systems' team demonstrated through many hours of front-end engineering and back-end finishing, made this effort manageable, efficient and cost-effective.

Craig Hatto, project director at Historic Royal Palaces, comments: "We turned to 3D Systems to provide the rapid throughput, accurate details and excellent finishing that was needed for this project. The engineering skill of 3D Systems' team, the opportunity to light-weight the dragon statues, and the material longevity of SLS 3D printing were key considerations for this project."

Research and development

Bringing the dragons back to life required a combination of research and reverse engineering by the company's On Demand Manufacturing team to enable rapid digital production of the parts. The project involved scanning a wood-carved dragon with a FARO Design ScanArm into Geomagic Design X reverse engineering software. The use of CAD enabled clever engineering techniques to be applied, including hidden features to facilitate mounting them to the pagoda, as well as a much lighter, hollowed form that is 60 per cent lighter than wood alternatives. The significant weight reduction enabled by 3D printing ensures less stress is placed on this historic building, thereby helping to preserve it for the future. The 3D Systems team also used the CAD data to scale the dragons, producing them in a variety of sizes from 1150mm to 1850mm in length.

Not only was weight an issue, but so was wind loading, particularly for the dragons installed near the top of the 50m-high Great Pagoda. To ensure the dragons would survive high winds and not exert excessive loads on the building structure, the team commissioned wind tunnel tests.

Nick Lewis, general manager of on demand manufacturing at 3D Systems, states: "In 3D printing, we are not limited by the need or time required to wait for tooling. The existence of digital 3D data gives us freedom to produce parts rapidly, and with custom sizes."

Manufacture, assembly and finishing

The dragons were printed in sections on 3D Systems' SLS machines in DuraForm PA, a durable polyamide 12 nylon material capable of producing a look and feel comparable to the original dragons. The resolution and mechanical properties of DuraForm PA make it an excellent candidate material for complex parts with thin walls or snap-fit requirements. In the case of the Kew dragons, these features suited both the functionality requirement of installation as well as the cosmetic requirements of the historic restoration. The 3D printed dragons were assembled and finished by 3D Systems' skilled artisans who hand-painted each piece, and gold-leaf details were applied by sub-contracted specialists.

Phil Schultz, senior vice president and general manager of plastics and On Demand Manufacturing at 3D Systems, says: "We so often see 3D printing technology applied to new innovations that when we get the chance to literally make history, it is quite exciting. In this collaboration with Historic Royal Palaces, we were able to bring new technology to bear on a historical landmark - restoring it to its former beauty and helping to ensure its future for generations to come. It is a testament to the capabilities and expertise of our On Demand Manufacturing team. Our full suite of durable materials, 3D printing technologies, reverse engineering software and practical expertise allow us to create a custom solution no matter how unique the customer's needs."

The Great Pagoda at Kew opens to the public on 13 July 2018. Follow the links to find out more about recreating The Great Pagoda dragons and 3D Systems' On Demand Manufacturing service.