Additive manufacturing (AM) has begun to affect nearly every industry, from healthcare to aerospace, making it possible to create unique geometries with unique properties. One industry where 3D printing’s impact is at an even more nascent stage in construction. There are firms and research groups exploring the use of 3D printing as a building technology, but additive construction is still so young that its exact purpose and benefits remain speculative and unclear. Why, other than for sheer novelty, squeeze concrete out of a nozzle to fabricate a building when you can rely on traditional methods?
Here we explore the various technologies currently being developed in additive construction to understand what the purpose, benefits, drawbacks and hurdles are to the technology.
Large-Scale Binder Jetting
Among the first large-scale 3D printers for construction was the D-Shape 3D printer, made up of a 6m x6m aluminum frame and 300 nozzles that spray a binding agent onto masonry material, such as sand. While D-Shape has printed some large-scale objects, including a 3m x 3m x 3m sculpture, the company has struggled to realize the vision of its founder, Enrico Dini.
Dini’s largest construction project to date, a 12-meter-long, 1.75-meter-wide pedestrian bridge, was performed in conjunction with ACCIONA and the Institute of Advanced Architecture of Catalonia (IAAC). The bridge is made up of concrete powder micro-reinforced with polypropylene and reflects a parametric design meant to optimize the distribution of material, while minimizing waste through the use of recycling raw material during the manufacturing process.
Rick Rundell, technology and innovation strategist, startup mentor and senior director at Autodesk, explained that the process used to fabricate the bridge might be more accurately described as 2.5D printing.
“Any of the companies that are making a go at 3D printing concrete really are kind of 2.5D printing concrete. They’re making custom panels by printing on a flat surface and giving it some dimension. Those panels are then intended to be tipped up and made into something,” Rundell said. “The railings of the bridge were 3D printed flat and tipped up, and then the bridge was cemented into place.”
3D Printing Metal
A pedestrian bridge is a good place to start when venturing into the world of 3D printing publicly used structures. Not as large as a single-family home, but not as small as an art object, a bridge can actually serve a useful purpose while demonstrating additive technology’s potential.
An additive construction that has received a great deal of attention is the MX3D Bridge, from Dutch firm MX3D. The project was unveiled in 2015 with an ambitious video depicting two industrial robotic arms standing on either side of a canal and welding a metal bridge until the two devices met in the middle.
Several years have passed since then, but the bridge is nearing completion. In the process, however, MX3D realized that the vision promoted in its initial video could not be created exactly as envisioned. Instead of printing the bridge live, on-site, the bridge has been fabricated off-site in a facility, where the industrial robotic arms would not be subjected to the elements.
“The MX3D Bridge project is a classic moonshot project,” Gijs van der Velden, CEO of MX3D, told engineering.com. “This means that we knew what we wanted to achieve, namely print a 12-meter bridge in stainless steel. We also knew that a lot of innovation was needed to bring the early stage technique up to the required level. We understood that our plan might have to be changed due to city permits or regulations. And it was clear that engineers, material researchers and other unforeseen external factors were going to change the original project plan.”
Unlike other projects that rely on plastics or masonry, the MX3D Bridge uses metal, introducing new advantages and challenges. van der Velden explained that the firm performed work with resin and concrete in the project’s early stages, before attempting metal.
“The form liberty that metal printing offers is greater,” he said. “Where concrete and resins only allow for a slight overhang as they require a longer 'drying' time, metal instantly solidifies and allows real 3D forms to be produced. The metals we use are 100 percent recyclable—not that I would want to recycle the bridge. Metal printing is relatively slow, but that will increase the drive on innovation to create more lightweight objects. Lighter equals faster equals cheaper.”
Like other additive construction projects, the MX3D Bridge promises a reduction in material usage, with van der Velden hoping for a 30 percent or more decrease in material usage. “In a world where material scarcity and footprint become bigger issues, a technology like 3D printing comes right on time,” he said.
Unlike other projects, the bridge also incorporates sensors to inform the physical properties and lifecycle of the structure. Created with Autodesk and The Alan Turing Institute, the sensor system built into the bridge will be used to conduct load testing—performed by Arup and Imperial College London—to determine how it behaves under dynamic loads and how the shape deforms when the bridge is overloaded. Additionally, the sensors will monitor the health of the bridge during operation, both while in use and underchanging environmental conditions.
MX3D and its partners, including the Lloyd’s Register Foundation, are also creating a digital twin of the bridge using “data from the FEA model, the material research, the testing data and the live feed” of the bridge, according to van der Velden.
“Combined, this data allows us to do thousands of additional tests in a virtual environment,” van der Velden said. “This way, we can generate much more development speed concerning the development of a data-centric design language.”
van der Velden believes that the biggest challenge for additive construction is design validation, before the start of production. “As all shapes are unique, a parametric method of validation needs to be built,” he explained. Without the need for preliminary destructive testing, we need to understand and prove the behavior of a tube with a variable thickness and changing organic geometry. For this, a data-centric design method is essential. The start will be hard, but as soon as we have a sizable amount of data, the development will speed up exponentially.”
The bridge is scheduled for completion in October 2018 before installation in its final location, likely spanning a canal in Amsterdam, in 2019. In addition to this project, MX3D is currently focusing on developing its 3D printing software and has several industrial, as well as infrastructural and art, projects underway in the Netherlands and the U.S.
Small-Scale Binder Jetting
San Francisco design firm Emerging Objects has relied on the material flexibility of binder jetting to conceive of new materials and design possibilities for additive construction. On its site, you’ll see a list of materials that include cement, ceramic, rubber, salt, sand, tea and wood.
In many cases, recycled objects were used as the feedstock, ground into a fine powder, and then printed into a new shape using a binding agent, thus giving new life to discarded goods. In a global social and economic system that overproduces and over consumes, recycling material is increasingly crucial. However, Emerging Objects also adds design elements to its 3D-printed objects that could bring new levels of sustainability to construction.
This enhancement is perhaps most evident in the “Cool Brick,” a ceramic brick designed to perform evaporative cooling. Made up of a network of lattices, the porous brick allows warm air to pass through it, where moisture passively collected from rainfall, cools the air and lowers the temperature within a building.
Unique to Emerging Objects’ approach to additive construction is its design of modular bricks and panels, which makes it possible to fabricate components with existing 3D printers. The firm has even gone so far as to use desktop 3D printers to demonstrate the feasibility of new construction methods with low-cost technologies. The Star Lounge is an example of a dome made from an assembly of modules 3Dprinted on MakerBot systems using biodegradable polylactic acid (PLA).
3D Printing Walls
While Emerging Object is 3D printing bricks and other modular elements, Branch Technology, out of Chattanooga, Tenn., is 3D printing walls. Well, to be more exact, the startup is 3D printing the insides of walls. Using a large industrial robotic arm attached to rails, the firm’s C-FAB process 3D prints lattice structures that are then filled with spray foam and coated in concrete.
David Fuehrer, director of sales &new business development for Branch Technology, added, “In addition to the foam and concrete, we are looking into other fill and finish materials for our composite development, but currently we are not at liberty to offer further detail.”
By 3D printing weight optimized lattice structures, it’s possible to create very lightweight components, while maintaining structural integrity, three to four times the strength of wood stud construction. Other benefits, according to Fuehrer, include “direct digital fabrication, lightweight assemblies, faster on-site installations, unprecedented design freedom.”Fuehrer also suggested that, by 3D printing these elements off-site before shipping them to the build location, it’s possible to control the fabrication process.
Branch Technology is focused on using C-FAB for prefabrication purposes,” Fuehrer said. “This allows for more efficient and accurate production. We can maintain better quality in our manufacturing facility, translating to faster on-site installations.”
The firm has participated in a number of smaller projects as it works its way up to constructing a crowd-sourced, single-family home design. This includes a 1,600-cubic-foot pavilion made in part with Oak Ridge National Laboratory, Thornton Tomasetti CORE and Techmer PM, and designed by SHoP Architects.
“Our previous projects showcase what is possible when combining parametric modeling with direct digital fabrication,” Fuehrer explained. “Each project pushes the boundaries of what is possible with this type of fabrication and provides us with opportunities to improve our processes in regard to moving projects from concept to final product.”
The pièce de résistance will be the 1,000-square-foot Curve Appeal home, designed by WATG’s Urban Architecture Studio and currently in development in Chattanooga. Selected through a crowd-sourcing competition, Curve Appeal will demonstrate the capabilities of C-FAB and freeform construction. WATG has tested a wall section for the design and the project’s groundbreaking is slated for 2018.
“In generic printed beam tests, a three-foot long beam could carry a load of approximately 3,600 pounds, while only weighing five pounds,” WATG wrote in a blog post from January 2018. “The freeform printed matrix is essentially a small space frame, making it highly efficient. The next stage will be to test the maximum load bearing qualities of each individual printed element of the structure.”
With respect to the hurdles related to Curve Appeal, Fuehrer said, “Our biggest challenge is also our biggest goal—to educate others within the construction industry on the advantages of our approach to additive manufacturing. As for a technical challenge, we are working to ensure proper integration of systems and equipment within our in-development composite wall system.”
3D Printing Whole Buildings
The ultimate goal, as exemplified by Branch Technology’s Curve Appeal project, is the ability to 3D print entire buildings. So far, there have been several examples of single-family homes that have been made with 3D printing. For instance, Arup and CLS Architects 3D printed a 100-square-meter home in 35 hours at the site of the Salone del Mobile design festival in Milan using a portable robot. The walls were printed individually in their final location, as demonstrated in the video below.
“The first thing people think about when they think about 3D printing for construction is a giant 3D printer,” Autodesk’s Rick Rundell explained. “You’re extruding out a building material, usually concrete. It’s sort of stiff enough to hold together, and you can gradually accumulate a structure of some kind. There’s a ton of challenges with that, of course. Concrete needs reinforcing to make any sense as a structural material, so introducing reinforcing into that is a challenge. Getting the concrete not to flow away from the nozzle so that it doesn’t make anything is a challenge.”
In instances in which concrete is the material being used, the nozzle may sport a special feature, such as a built-in trowel, that will keep the material from flowing too much. In the video above, you can see the manufacturing team occasionally using a spatula to clean up the material as it flows. Companies may also use special, often proprietary quick-setting cement for these projects.
An expert in concrete 3D printing on a large scale is WinSun Global, a Chinese company that has repeatedly garnered a great deal of attention for a number of projects that include 3D printing 10 houses in 24 hours, a five-story apartment, a 1,100-square-meter villa, and an office building in Dubai. In all of these cases, the buildings were unveiled suddenly and little was revealed about the exact nature of the printing process involved.
Speaking to WinSun’s recent partner in additive construction, AECOM, we did learn a bit more about the technology. Antonio Ng, AECOM’s executive director of innovation for Greater China, relayed that AECOM and WinSun had signed a memorandum of understanding that will see the two companies work together on future construction projects.
As part of the partnership, 56 members of AECOM from around the world went to WinSun’s facility in Suzhou, China, where they split into seven teams to learn about the use cases and applications of 3D printing.
“It was a very fruitful event for us,” Ng said. “A lot of great ideas came out of it, ranging from applications related to buildings, urban intervention, infrastructure, as well as disaster relief. One of those ideas eventually took the international runner-up prize for the CIC Construction Innovation Award in Hong Kong in 2017. We felt that this kind of hands-on exploration can really help build momentum for us when we find a suitable pilot project and clients to push this technology in AEC forward.”
Ng said that the printer installed at the facility was about 115 meters long, 10 meters wide, and 7 or 8 meters high. Components for buildings constructed by WinSun are first produced in a temperature- and humidity-controlled facility from “proprietary glass-fiber reinforced concrete with high plasticity and made from recycled building and mining waste,” according to Ng. They also have different mixtures for different applications. The elements are then shipped and assembled on-site.
“My understanding is that since they have developed second- and third-generation printers that can be deployed on-site and even deployed on high-rise projects. I haven’t seen those second- and third-generation printers firsthand, but I have seen videos of them in action,” Ng said.
AECOM’s Asia-Pacific region is now in the process of settling on clients and projects where 3D printing might make sense. So far, Ng believes, the United Arab Emirates seems to hold the most potential for such an endeavor, given the government’s focus on additive construction and its goal of 3D printing 25 percent of new buildings by 2030. The partners are also discussing the development of testing procedures and standards that can be used throughout additive construction.
“There are so many unknowns. We’re seeing a very long up-front process in making sure that the client understands what we’re getting into together,” Ng said. “Unlike a conventional project, it’s clear that we’re approaching this project hand in hand, and some of it is going to involve going into unchartered territories. There’s going to be testing involved, an iterative process. That’s unavoidable at this point if we’re talking about anything beyond a single dwelling house.”
While the Asia-Pacific side of AECOM is still in the exploratory phase, AECOM Hunt in North America has been working with additive construction since 2011. The company has already used the technology to construct a series of cells for multiple prisons in the U.S. and is in the process of 3D printing various components for hospital rooms in Ohio.
Russ Dalton, BIM director for the Americas, understands additive construction as a form of prefabrication. Prefab has made it possible for AEC firms to better control the build process by making construction more like manufacturing. Producing standardized elements off-site, in a controlled environment, leads to improved quality assurance, stricter adherence to budget and schedule, more efficient installation on-site, and improved worker safety.
For this reason, AECOM is exploring 3D printing infrastructure elements, as well as buildings. This is especially essential given the dangerously dilapidated condition of U.S. roads and highways.
“I’m looking at a nearly 100-year-old, half-mile-long bridge in Delaware that goes over an active roadway in a populated area,” Dalton relayed. “We have to replace that bridge yet keep it operational, and there are businesses under it. In conventional construction, you would go in, lay down places for steel and bring in the concrete processing plant. We don’t have room for that. So, let’s 3D print those sections and drop them in place as we go. That’s utilizing lean construction and just-in-time delivery.”
Jillaine Tuininga, senior marketing and communications director for the project technologies group at AECOM, added, “When it comes to the build as well, it allows the actual time on-site to decrease, which lowers safety risks because you have a very clean operation. [The 3D-printed elements] arrive on-site, you connect them up, you get your disciplines to come in quickly after that. It really can tighten up that schedule on-site as well, which carries over to safety.”
From Digital Construction to Physical Construction
Dalton sees AM as fitting into a larger vision of digital fabrication. With extensive experience in building information modeling (BIM), Dalton stresses the importance of quality 3D models in the construction process.
“Our opinion at AECOM is that we build it twice—the first time virtually and then physically,” Dalton said. The introduction of other emerging technologies, like virtual and augmented reality, further weave a digital thread through the design and construction process.
Designing in BIM offers operational, cost and design intelligence, while virtual and augmented reality make it possible to realistically visualize a project before it is completed. When it comes to the hospital currently in development, this means the ability to virtually fit beds and wheelchairs in a hospital room to better understand the size constraints of the room. Finally, the digital model can be directly fabricated with 3D printers, which Dalton says provides a physical construction that has a one-to-one match with the digital model.
“In one of our warehouses, we have a stick-built patient room and then we have the exact replica as a 3D build—the same room,” Dalton said. “You can walk the client through each; they see the quality of one as compared to the other. They see the flexibility of the additive process and that we haven’t lost any craftsmanship.”
Rick Rundell, from Autodesk, believes the tighter connection between the design software and the actual fabrication process gives the actual designer more control over the construction process.
“One interesting subject for us, as a company that makes tools for design, is that we’re now also making tools for making things because those design tools are being used to directly fabricate things,” Rundell said. “How does that ability—that digital workflow—directly enable a different kind of design that requires a tool that works differently in some way? How will our tools support a process where designers directly fabricate the things they design, as opposed to producing drawings of those things?”
Rundell pointed to generative design as a key concept that may be increasingly exhibited in additive construction. Projects already discussed here have employed some form of computationally influenced design, with simulation-driven algorithms dictating where to place or remove material. With generative design, it’s possible to have software create a number of different shapes based on certain design constraints before one is ultimately selected. In most cases, these geometries can only be made with AM.
The Future of Additive Construction
This brings us to the direction that additive construction is headed. So far, the completed buildings made with AM are not all that unique looking. And, when they are, headlines from mainstream media outlets may brand them “the ugliest [such and such] you’ve ever seen.”
As Rundell pointed out to us, “I’ve run into buildings that look the way they do because of the limitation of additive, but I haven’t run into any buildings yet that reflect an opportunity that would not have been achievable had the additive process not been used.”
It's possible that, as the technology matures, these architectural elements will take on more aesthetically pleasing shapes. Perhaps these shapes will be created using generative design, optimized for strength, weight and material usage. This would be obviously beneficial in terms of both cost and reducing environmental impact.
In terms of prefabrication, firms could speed up construction, stick to budget and schedule, and protect workers by limiting time spent in precarious places high above the ground.
New materials and processes may also be developed, as we have already seen. Rundell has a perfect vantage point for some of these innovations from his office at the BUILD (BUilding, Innovation, Learning and Design) space in Boston, Mass. While overseeing the development of the space, he’s witnessed a number of firms who use the facility’s construction tools take an interest in additive construction.
“Research teams from both Harvard and the Architectural Association School of Architecture in London doing work kind of modeling additive processes applied to concrete, using ceramics at a smaller scale,” Rundell said. “We had a team from MIT that did interesting work not in 3D printing concrete itself, but 3D printing the formwork for the concrete out of a two-component foam. The team would print the two-sided form and then fill it with concrete, so you would end up with a concrete wall that was insulated on the sides by the foam. They prototyped that process using a tracked robotic vehicle designed to be used on construction sites.”
Rundell, however, doesn’t necessarily believe that AM will ever reach the scale of printing high-rises—despite Nanyang Technological University’s plans to 3D print high-rise public housing in the near future.
“I think it’s unlikely that building at [the scale of our eight-story offices] will ever be additively built out of some sort of homogenous material like concrete. I think what we’ll see [is] additively fabricated components in buildings—maybe large components like facades or panels,” Rundell said. “In practical terms, what we’ll find is that components that make sense to be additively fabricated will be additively fabricated off-site and brought to the site and either assembled or mounted on a frame or some kind of supporting structure to create an enclosed building.”
According to Rundell, that doesn’t mean that we shouldn’t dream big, though.
“Even though I think that 3D printing whole buildings would be very challenging, I love the fact that people are thinking about it at that scale. I think we’re going to learn a lot. Maybe it’ll turn out that we do 3D print buildings at scale, but we will learn a huge amount about how to apply these ideas to the building industry,” Rundell said.
“There are also challenges with how to produce inhabitable structures on Mars or the moon using versions of 3D printing that I think are fascinating and may turn out to be very applicable to terrestrial conditions, as well. So even though some of these things seem pretty speculative, I think there’s a huge amount of value to pushing the envelope in that way.”