MIT advances 3-D printing with variable density concrete and progress to machines to build machines

Over the years, three MIT researchers and one of the companies that licensed the MIT patent, Z Corp., added new variations to 3d printing, including the ability to include colors in printed objects and to use a variety of materials. The ability to print metal objects, in particular, extended the technology from just a way of visualizing new designs to a means of manufacturing metal molds used for the injection molding of plastic parts.

Manufacturing companies took a strong interest in this work because it enabled “doing a complete design for a tool in days, rather than months,” he adds. “That means you can afford to go through more design iterations.”

Time for a snack

3DP has since branched out in a wide array of directions, at various companies and research institutions around the world. Applications have included everything from the printing of customized prosthetic limbs to nanoprinting of tiny machinery to a project at the MIT Media Lab developing machines to print food ranging from candies to complete meals. One former Media Lab student, Peter Schmitt PhD ’11, working with Media Lab IP consultant Bob Swartz, has printed entire working clocks — with all their gears, chains, faces and hands in a single unit — ready to start ticking as soon as the surplus powder is washed away.

“Mass production is only a couple of hundred years old,” Swartz says. Now, “we’re moving into an area where things will no longer be mass produced.” With 3DP, a basic pattern can be modified to fit an individual’s size, fit and personal tastes before printing.

These clocks were primarily intended to demonstrate that complex devices could be printed as a unit — but one clock took about 100 hours of printing time to produce. “That’s completely impractical for any kind of mass production,” Swartz says, “but it’s my belief that one can get orders-of-magnitude improvements” in the production speed. “It changes the way we think about production.”

Printing Concrete

Concrete samples made by hand to illustrate the concept of density gradient in concrete. A team from the MIT Media Lab hopes to be able to print such materials with a 3-D printer. Photo: Steven Keating, Timothy Cooke and John Fernández

Printing concrete techniques could also allow the properties of the concrete itself to vary continuously, producing structures that are both lighter and stronger than conventional concrete. Graduate student Steven Keating has already made sections of concrete with the same kind of variations of density.

Variable-density printing is not just about large-scale objects. For example, Oxman has used a similar system to produce a glove with sections that are stiff and others that are flexible, designed to help prevent the wearer from developing carpal tunnel syndrome. She has also designed a chair made of different polymers, producing stiff areas for structural support and flexible areas for comfort, all printed out as a single unit.

Peter Schmitt, now a visiting scientist at the Media Lab, is pushing the technology in an even more sci-fi direction, trying to “build machines that could build machines,” he says. So far, he’s succeeded in making machines that can make many of the parts for another machine, but there remain many obstacles in establishing connections among these — and it’s still more of an intellectual exercise than a practical system, he concedes. “There are better ways to make the parts,” he says. “But at some point, these kinds of things will happen.”

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