3D Concrete Printing and Digital Construction
There are three methods for 3D printing: stereolithography, patented in 1986: fused deposition modelling, patented in 1989: and selective laser sintering, patented in 1992. It didn’t take long before research into 3D concrete printing (3DCP) began, focused on developing the equipment needed and the performance of the materials used. Twenty years later there were over a dozen experimental prototypes built, extensively documented in the 2019 book 3D Concrete Printing Technology: Construction and building applications,[i]which also has details on the materials science required to identify successful mixtures and admixtures. The information needed to create a 3D blueprint is generated during design, and it is a relatively small step to move from a BIM model to instructions for a 3D printer.
By 2022 the commercialisation of 3DCP was underway, with two types of systems available. One using a robotic arm to move the print head over a small area, intended to produce structural elements and precast components, the other a gantry system for printing large components, walls and structures. The Additive Manufacturing Marketplace had 34 concrete printing machines listed, ranging from desktop printers to large track mounted gantry systems that can print three or four story buildings. Companies making these machines are mainly from the US and Europe, and the table also has details on the type and size of a selection of machines. There are also several companies offering 3DCP as a service at an hourly or daily rate.
One of the most advanced 3DCP companies is Black Buffalo, a subsidiary of South Korea’s Hyundai group based in New York. Their NexCon gantry system takes around 11 hours to build and eight hours to take down. Using a proprietary ink developed over a few years of research involving a lot of trial and error (and getting approval for building codes), the machine can print up to four stories with a crew of five people. One person is required to monitor the nozzle and insert stiffening frames every few layers to provide structural strength, the pump needs two people and a helper, plus a site foreman or engineer. As well as walls it will print floors and precast elements. Black Buffalo expects to sell over 100 of these printers in 2022-23, and they are available for rent at $1,000 a day.
Some companies making 3D concrete printers
Concrete printing is only one part of the development of additive manufacturing. In mid-2022 the Additive Manufacturing Marketplace listed 2,372 different 3D printing machines from 1,254 brands. The number of printers and materials used were: 364 metal; 355 photopolymers; 74 ceramic; 61 organic; 34 concrete; 24 clay; 20 silicone; 19 wax; and 19 continuous fibres. Many of these printers could be used to produce fixtures and fittings for buildings. Producing components onsite from bags of mixture avoids the cost of handling and transport, and for large items avoids the load limits on roads and trucks. There are also printing services and additive manufacturing marketplaces being set up. These link designers to producers with the materials science, specialised equipment and print farms capable of large production runs and manufacture on demand. Examples are Dassault Systems 3DExperience, Craft Cloud, Xometry, Shapeways, 3D Metalforge, Stratasys and Materialise.
Additive manufacturing is a major part of a broader system of production known as digital fabrication. Neil Gershenfeld described digital fabrication as turning ‘bits into atoms and atoms into bits’ using fabrication laboratories (fabs) producing ‘assemblers’ that provide the cutters, printers, millers, moulders, scanners and computers needed for designing, producing and reproducing objects. These tools include traditional subtractive ones for cutting, grinding or milling, but the focus has been on research into new methods of additive manufacturing using different methods of layering materials using 3D printers. Printing of metal, ceramic and plastic objects from online design databases is spreading from hobbyists and initial users to industry applications and wider acceptance.
Gershenfeld, who founded the first fab in 2003, defined digital fabrication, as ‘the seamless conversion of design and engineering data into fabrication code for digitally controlled tools.’ The definition in a Construction 4.0 book is less focused, a ‘method or system which relies on digital fabrication entirely or to a significant degree, either in prefabrication or on-site construction. Examples of digital fabrication processes in construction include robotic fabrication and assembly, large scale additive manufacturing, and the use of specialized automation systems for material processing in areas ranging from advanced fabrication of metal or timber assemblies to various forms of concrete processing to the fabrication of multi-material composites.’ The chapter on digital fabrication has over a dozen examples, with many of the projects shared with other chapters in the book on 3D concrete printing, robotics and automation.
At is broadest, digital fabrication is any means of turning design information into physical products using automated processes. There is a well-established global maker movement behind the growth of digital fabrication. In 2009 the Fab Foundation was established at MIT as a non-profit with annual conferences and providing educations and training. The Foundation coordinates an international network of 1,500 fabrication laboratories (fabs) in 90 countries, many in university design and architecture schools, and the ‘FABLAB Movement’ is an even broader collaborative effort that includes hobbyists and tinkerers working on digital design and fabrication code. This network takes existing technologies used in fabrication like cutting, milling and rolling done by numerically controlled machines, which have been around for decades, but uses them for design, which is new. The digital linking of design to fabrication is the beginning of another stage of development. The World Economic Forum also has a network of 14 Centres for the Fourth Industrial Revolution, and Autodesk has three BUILDSpace laboratories. The 2017 UK industrial strategy included funding for a manufacturing hub and along with aerospace and automobiles targeted construction, 3D concrete printing and OSM.
Gershenfeld argues digital fabrication will follow a similar exponential development path as digital computers, with the number of fabs doubling every two years and their cost halving, making local production of many objects and items possible. Gershenfeld suggests the technology is now ready to become widespread, and is at a similar stage to PCs in the early 1990s:
Digital fabrication shares some, but not all, of the attributes of communication and computation. In the first two digital revolutions bits changed atoms indirectly (by creating new capabilities and behaviours); in the third digital revolution, the bits will enable people to directly change the atoms …. Across the global network of fab labs, we can already see a steady stream of innovations around cost-effective models for individuals and communities to make clothing, toys, computers and even houses through designs sourced globally but fabricated locally.
Digital fabrication is at or close to the tipping point, as its use extends from hobby to experimentation and adoption. Just as concrete in the early 1800s moved from the fringe toward the centre of construction as the underlying technology and equipment improved, fabs can follow a similar path over the next few decades of the twenty-first century. Although Construction 4.0 concluded ‘Today, industry adoption of digital fabrication is still very limited and is not deployed at scale in the industry’[vii], the technology is advancing rapidly and many demonstration 3D concrete printing projects have been completed successfully. In a 2020 report that has many examples of current use, ARUP argues: ‘The opportunities unfolding with digital fabrication not only demonstrate new techniques in full-scale pavilion fabrication, but also provide new methods to solve design, business and societal challenges. Arup is one of a number of specialized consultants providing digital twins and design to fabrication capability on projects.
Onsite and Nearsite Production with Digital Fabrication
Digital fabrication is a technology whose use has a high probability of becoming ubiquitous. In construction, the focus so far has been on 3D printing of concrete, with experimental systems by the early 2000s,[ix] and by 2019 there were over a dozen examples of buildings completed using the technology.[x] However, the potential of 3D printing in construction is not limited to concrete. Once a BIM model of a project has been created it can be used to provide instructions for production of both structural and decorative components of a building. Mobile digital fabs in shipping containers can produce some of those components onsite. Local firms offering manufacturing on demand from print farms can produce large runs or specialised components, a nearsite form of production rather than OSM.
The combination of digital twins and digital fabrication would be transformational if it allows onsite and nearsite production of some or many building components, by fundamentally altering existing economies of scale in the industry. As well as 3D concrete printing, other materials like steel and plastic can be used to make components and fittings on or near the building site. A modular fab in a container customised for construction, or even a specific construction project, can be set up onsite to produce components as the schedule requires. Large sites might need a fleet of fabs. Restorations and repairs can be done with replacement parts made onsite from scans of the original.
Mass production will always have a role, but market niches currently occupied by some or many manufacturing firms may be replaced by new production technologies based on BIM, linking localised digital fabrication facilities with online design databases. Combined with robotic and automated machinery and assemblers, digital fabrication and standardised parts opens up many possibilities. Adding new materials to the 3D palette through molecular design and engineering, or upgraded versions of existing materials, may unlock other unforeseen design and performance options.
If this eventuates some, possibly a great deal, of the current construction supply chain based on mass-production of standardised components will become redundant. For example, an onsite or nearby fab with printers and moulders might produce many of the metal, plastic and ceramic fittings and fixtures for a building during its construction. These parts might be delivered by autonomous vehicles. The digital twin of the project, which might be outsourced, can link the design and fabrication stages to the site and the project. Digital fabrication produces components and modules designed to be integrated with onsite preparatory work and assembled to meet strict tolerances. Project management would become more focused on information management, and the primary role of a construction contractor might evolve into managing this new combination of site preparation work and integration of the building or structure with components and modules, some of which may be produced onsite in a fab if economies of scale permit. The strength of this effect will be determined by those economies of scale. Beyond site preparation other site processes may be restructured around components and modules that are designed to be assembled in a particular way, and machines to assemble those components and modules can be fabricated for that purpose.
If onsite and nearsite production becomes steadily cheaper the industry would, perhaps slowly, reorganise around firms that best manage onsite and offsite production and integration of digitally fabricated parts. Contracting firms would become more vertically integrated if they are fabricators as well, reinventing a business model from the past when large general contractors often had their own carpentry workshops, brick pits, glass works and so on. With outsourced business processes and standardized site and structural work, that fabrication and integration capability would be a key competitive advantage of a construction firm. Firms will be integrating automated production of components with design and construction using offsite manufacturing and onsite fabrication, using platforms that coordinate building design and specification with manufacturing, delivery and onsite assembly. Open platforms will be like new digital ecosystems. Closed, internal platforms will be developed by larger, vertically integrated firms with the resources to manage the system.
Industrialised materials like concrete, steel and glass affected the organisation of onsite processes as they were improved with incremental innovations. The development of digital fabrication should follow a similar path to concrete, where over decades the machinery (mixers, pumps), processes (formwork systems) and materials (reinforcement, concrete strength, setting agents) were developed. Growth in digital technologies is faster than analogue, so instead of the many decades of innovation taken for concrete technology to develop, it might take a decade for digital fabrication to become cost effective if the cost of fabs falls and the supply chain of raw materials develops as it did for personal computers in the 1990s. Contractors would become more vertically integrated as they also become fabricators, managing a combination of onsite and nearsite production to deliver projects.
ARUP, Designing with Digital Fabrication, 2020: 8. Gershenfeld, N. 2012: 45. How to Make Almost Anything: The Digital Fabrication Revolution. Foreign Affairs, 91(6), pp. 43–57. Gershenfeld, N. 2017. The Science, and The Roadmap, in Gershenfeld, N., Gershenfeld, A. and Cutcher-Gershenfeld, J. Designing Reality: How to Survive and Thrive in the Third Digital Revolution, in New York: Basic Books. 95-116, also 159-182.
Kaseman, K. and Graser, K. 2020: 187. Digital fabrication in the construction sector, in Sawhney, A., Riley, M. and Irizarry, J. (eds.) Construction 4.0: An Innovation Platform for the Built Environment, Abingdon: Routledge. Sanjayan, J. G., Nazari, A. and Nematollahi, B. 2019. 3D Concrete Printing Technology - Construction and Building Applications. London: Elsevier.