Advances Made in Mega Freeform Construction
The potential of large-scale freeform construction is to build a full-scale house in a day at a fraction of today's cost. The current reality of mega layered manufacturing is it delivers more modest benefits: the ability to build designs that are difficult or impossible to construct (think Frank Gehry) using conventional techniques. In this way, large-scale freeform fabrication mimics its smaller, older cousin of rapid prototyping and rapid manufacturing, except the technology is not as mature.
One of the more exciting players in the mega 3D printing industry is Enrico Dini. The Italian engineer's d_shape (formerly Monolite) technology combines sand
Dini deserves special recognition because his UK-based Monolite UK Ltd company is actually printing large outdoor sculptures and structures. Reached by cell phone in his native Italy, 47-year-old Dini excitedly tells RapidToday about a gazebo-like sculpture he is building in five pieces for the interior of a roundabout in Pisa (see photo at left). "We started printing yesterday," he says in mid-July. The sculpture will be made of five component pieces, each about 6.5 meters high.
The printing is slow because Dini doesn't yet have a working feeding system for the sand. "We are able to print just 15 cm/day on six square meters," he says. Sand is manipulated by hand, 60 liters at a time. "Once proper feeding system will be made available, we shall print up to 50 centimeters per eight hours on 30 square meters." The printing resolution is about five dpi, with a goal of eventually reaching 25 dpi.
The gantry-mounted print head holds 300 servo-driven nozzles which spray an inorganic binder into a pattern specified by the 3D CAD STL file. When combined with a powdered catalyst that is mixed with the sand, a material with a tough microcrystalline structure emerges. It has a compression strength around 500 daN/cmq and a tensile strength around 50 daN/cmq, according to Dini. The material starts to harden in about 15 hours, and is completely solidified in 24.
When Dini first developed the technology in 2004, he used epoxy for the binding agent. The resolution was good, but the resulting material was expensive, flammable, and environmentally noxious. Dini won't disclose the composition of his new binder, but does reveal it was developed from a product used by the artificial stone industry.
Besides the sculpture in Italy, Dini has also built some six-square-meter "test pieces" for Freedom of Creation, the Dutch rapid manufacturing design house, and is scheduled to build a 1,000-cubic-meter villa in Porto Rotondo on the Italian island of Sardinia. "If authorities will give permission, the villa will be printed in about three months and hopefully assembled next year using Sardinian granite," says Dini.
Dini says it's not too soon to start thinking about licensing the technology. He estimates potential licensees will pay about $1-2M USD per region, plus royalties.
Dini might be in for a wait if Dr. Behrokh Khoshnevis' experience finding cash is any indication. Khoshnevis is the University of Southern California inventor of Contour Crafting, a layered fabrication technology that uses concrete to build houses and other structures.
"It's hard to carry this technology forward in a university environment with part-time students," remarks Khoshnevis. "For every experiment, we spend three or four hours cleaning up." He figures a successful enterprise would require at least 20 employees.
Despite funding setbacks, Khoshnevis is placing his bets on his technology. It's faster than the d_shape process, he says, and it's based on a proven material - concrete. "We didn't want to introduce two new things - a new process and a new material," he says. "The material has already demonstrated itself over a couple centuries." Not that a little tweaking isn't necessary - a special undisclosed chemical is added to standard concrete to improve pumping characteristics and help it set up faster.
Contour Crafting has used its robotic gantry to build a number of structures. "Right now, we don't have much of a technology issue," says Khoshnevis. "It just has to be optimized and ruggedized. Something developed in the lab is not necessarily good in the field. Imagine your SLS [selective laser sintering] machine operating in the wind, rain, and dirt." Also not finalized is the technique for embedding the necessary electrical, plumbing, and air conditioning conduits in the building's walls.
Not yet optimized on earth, Khoshnevis and Dini already dream of rapid manufacturing buildings in space as well. "The problem is that NASA right now has a concentration on crew transfer," says Khoshnevis. "The next phase would be construction of facilities on the moon." The European Space Agency is closer, he says, and has even mentioned Contour Crafting in a request for proposal.
Also working hard on an oversize three-dimensional print technology is a Loughborough University group led by Dr. Richard Buswell. The Freeform Construction Project is a four-year one-million-pound study of mega-scale additive processes for printing full-sized building components.
The Loughborough technology is called "concrete printing," and is being developed to handle cement, gypsum, and other materials. Two-and-a-half years into the project, Buswell now has a development prototype which prints with a fine 6mm layer depth. "We are currently preparing to print a 'large' freeform compression structure (a wall) to demonstrate progress to date," Buswell relates by email. The wall will be about 2m x 1m x 1.5m high, and will weigh a hefty 1.5 tonnes, or 3,300 pounds.
Buswell is partnering with the construction industry to build not full-scale buildings, but rather architectural components, like cladding panels, that will be pieced together. "Buildings will always be an assembly of components, particularly large buildings," he says. "I believe that the market application will initially be in high-end architectural engineering, rather than the domestic [house] market."
"At the end of our study we hope to demonstrate large-scale component manufacture to the industry and demonstrate the printing process, which will hopefully lead to commercialisation," concludes Buswell.
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