Homes to Order

3D printing and additive manufacturing are rapidly becoming big business in the consumer, medical and aerospace industries. A few pioneering individuals and companies are now attempting to achieve the same in the construction industry as well. Eric Payne reports.

The deeply religious Catalonian architect Antonio Gaudi believed that ‘originality consists in returning to the origin’, a statement with overtly spiritual overtones given his background and personal philosophy about life and the universe. That was part of what led him to design buildings akin to organic structures, replicating forms found in nature. But while his imagination might have been unbounded, what he was actually able to create was limited by the technology of the time in which he lived.

Low-volume, high-value, personalised production, which does not require high levels of capital investment, tooling or inventory are just some of the vaunted capabilities of 3D printer technology, as distinct from traditional high series mass production which leverages economies of scale. Less commented upon in the mainstream press but equally as important for industry is the geometric complexity of the structures enabled by additive manufacturing.

Indeed, ambitious architects are beginning to recognise that 3D printer technology trumps traditional building approaches every time with respect to the necessary trade off between geometric complexity and cost. The ability to develop designs with topologically optimised geometries promises to usher in a new era of ingenuity, enabling architects to create structurally stable honeycomb and skeletal structures (among others) just by fusing the right amount of powdered material.

Making the virtual a reality

Used as a verification tool by architects, engineers and design houses since its inception, the ‘rapid prototyping’ technology first patented by Chuck Hull in 1986 has come on leaps and bounds in recent years, transforming from 3D printing into much more formal-sounding additive manufacturing. Some of the possibilities being seriously pursued by academic institutions and commercial vendors would have been unthinkable just 10 or 15 years ago.

D-Shape, which is a new building technology developed by Italian architect Enrico Dini, is one such solution. Using sand and a specially developed inorganic binder to create large stone-like structures from 3D CAD drawings simply by pressing ‘Enter’, it promises to ‘revolutionise the way architectural design is planned, and building constructions are executed’. One cannot help but wonder at the kinds of buildings an innovative architect like Antonio Gaudi – famed for his unique combination of Gothic and curvilinear Art Nouveau forms – might have created had he had access to a similar technology.

But it is not only in the area of architectural elements that the technology might be applied. One of the most advanced 3D building projects in the world is Contour Crafting, which emanates from the University of Southern California and has already received funding from Caterpillar Inc. and NASA. Developed by Behrokh Khoshnevis, a professor of engineering and director of the Center for Rapid Automated Fabrication Technologies (CRAFT) at the University of Southern California, the system uses a 3D printer nozzle that spits out concrete to automatically ‘print’ a new house in less than a day, complete with embedded conduits for electricity, plumbing and air conditioning. “Initially it will be most beneficial to developing countries to eradicate their slums. Next is emergency shelter construction where war and natural disaster uproots thousands of people,” Professor Khoshnevis told txchnologist.com. “[It] can build much cheaper and much faster and can produce dignified housing rather than tents and boxes.”

If it were to be deployed at any sort of scale, this kind of 3D printer technology would transform the construction industry beyond almost all recognition. The need for certain types of construction equipment – cranes, pumps, concrete mixers, moulds, formworks and pre-fabrication technologies – would be largely eliminated, and the requirement for skilled manual labour and project managers capable of understanding and following complicated blueprints significantly reduced. Such a reduction in the requirement for material, equipment and skilled labour would be likely to make it easier for developers to ‘build’ low-cost housing for poorer sections of the community, or in disaster-hit areas, while also having a profound impact on existing supply chains and the labour market.

The biggest concern that any such technology will need to address is around the structural stability and longevity of whatever it might create. Governments in developing countries are under increasing pressure to provide suitable low-cost housing for their increasingly urban populations, as people from the countryside cluster around big cities such as Johannesburg, Rio de Janeiro and Nairobi in pursuit of jobs and a better quality of life. All too often, governments and housing institutions have been tempted to provide short-term solutions in the form of houses made out of cement or fibre-board, christened ‘hot boxes’ by their detractors because of poor thermal efficiency – too hot in the summer, too cold in winter. The prospect of a low-cost 3D printed house with sound structural stability and a good level of thermal efficiency would probably be a killer application for the technology in its proposed target markets.

This is an area that will need careful supervision and oversight from the (understandably) conservative codes and standards bodies that have the responsibility for regulating house and office building.

Opportunities and challenges

One of the key challenges involved in bringing additive manufacturing to a broader market is access to suitable raw materials. As such, engineers and technologists have already committed a substantial amount of time and effort to extending the range of materials 3D printers are able to utilise. Some of the largest slums in some of the poorest countries in the world already have well developed networks for collecting, grading and recycling PET bottles, polypropylene and nylon waste, much of which is shipped and dumped by Western companies in the first place. “An awful lot of ABS (Acrylonitrile Butadiene Styrene) is beginning to appear in dumps around Africa,” Dr Phil Reeves, Managing Director of UK-based 3D printing consultancy Econolyst Ltd., outlines. “Given that ABS is one of the feedstuffs for many of the low-end additive manufacturing machines, it is not inconceivable to think that there might be opportunities for local entrepreneurs to create very good businesses recycling low-value waste into much higher value raw material feedstock. One of the things that we are looking at very seriously as part of the 3D4D Challenge is the free trade of recycled African waste back into Western supply chains.” The issue arose again when Econolyst worked with DSTL (Defence Science Trading Laboratory) and the MoD to determine what role additive manufacturing or 3D printing might play in future warzones and conflict zones. “One of the major areas of focus for that research was concerned with the availability of material resources and the possibility of adapting designs to achieve similar functions using different materials.”

The long-term commercial opportunity as defined by Dr Reeves is going to be in both metal and polymer trading. “If one looks at the volumes of 3D printed/additive manufactured parts, the big polymer applications – iPhone cases and the like – are not made from ABS but nylon laser sintered powder,” he remarks. The ability to better exploit new and different materials is the hinge upon which the future of the wider additive manufacturing industry depends. Current 3D printing systems can create prototype, semi-finished and finished component parts out of polymers – thermosetting (epoxy) and thermoplastics (ABS, nylon, PP, PMMA, PC, PEI, PPSF, PLA); metals – ferrous (tool steels) and non-ferrous (stainless steel, titanium, aluminium, super nickel alloys); ceramics – gypsum, alumina, silicon carbide; and organics – waxes, cellular materials. This in itself is a massive increase in the range of operational capabilities that were considered state-of-the-art just two or three years ago, and both the D-Shape and Contour Crafting projects are confident that cement can be utilised in a similar fashion.

If the technology is going to be successfully adopted by the manufacturing industry and maybe even the building industry, to enable the creation of 3D printed architecture, it will also have to develop beyond its legacy as a prototyping technology. “In many ways, this is still a very immature technology,” Dr Reeves reflects. “We are still largely trying to use prototyping machines to do production manufacturing. Things like closed-loop control, in-process feedback and the ability to validate manufacturing processes still have significant limitations. Whereas a Haas CNC machining centre, for example, has quotable tolerances of plus or minus two microns and if it starts to go out of tolerance, it ‘knows’ that it is going out of tolerance and it has closed-loop feedback to offset that change. We do not have that yet within additive manufacturing, and that causes problems if you are proposing to deliver high-risk applications.”

This is an active area of research and development and one that is moving forward quite rapidly, given the historically high levels of investment in the sector. However, process monitoring and in-process control are only part of what is happening in the labs. “We are only now beginning to understand what is happening in the melt pool, what it is doing to the final part and how the geometry of the part actually impacts on things like the metallurgy of the part,” Dr Reeves tells us.

Another tool

Digital design tools have enabled architects to optimise the geometry of component parts for a number of years, but 3D printer technology now makes it possible to realise those kinds of designs in full. Of course, it is important to recognise that neither D-Shape nor Contour Crafting have yet produced a fully functioning machine that matches all of the capabilities promised by their designers. But the potential is impossible to ignore and certainly deserves serious attention from those working in the industry.

There are concerns among some about the structural stability of a 3D printed concrete structure without wire mesh or rebar to provide additional support. To that end, the codes and standards bodies responsible for regulating the building sector to ensure consumer safety and compliance will almost certainly slow adoption. Non-structural components that add to the aesthetic value of a building are likely to be developed first, with full 3D printed houses not likely to follow until the technology can meet a minimum required standard. In 10 to 20 years, however, 3D printed buildings may be just another option, available to be deployed at scale.