Metallic Laser Printing Tested To Fabricate Structural Nodes
Industries ranging from medical equipment manufacturers to aerospace are increasingly using 3D printing for the fabrication of intricate and costly objects. In Europe, designers are exploring the technology for use with construction-element production, as well.
Dan Kirk, direct metals manager at 3D printing firm CRDM Ltd., High Wycombe, U.K., says printing is not going to replace traditional processes for steel work, but "it will give you the opportunity to create designs that you couldn't previously do."
CRDM recently printed a prototype steel structural node for a Netherlands-based team of London's Arup Group Ltd., which is funding its own in-house 3D printing research. The team's interest stems from a project to design a lighting canopy of rods and stressed cables over a street in The Hague, says senior designer Salomé Galjaard.
Fabricating 1,200 differently shaped canopy nodes by traditional methods—with each shaped around a central tube and having six or seven welded-tab connections—would be a major task, says Galjaard. So, she used her industrial design skills to explore a form of 3D printing called laser sintering.
The technology involves spreading metal powder inside a chamber in layers as thin as 20 microns. A computer-guided laser beam then follows a path across the powder specified by the digital design. The heat of the beam "sinters" particles in its path by heating them just to the temperature at which they bond together at the molecular level.
Another layer of powder is laid down, and the process repeated, fusing particles into the final shape. At the end of the process, the designed part sits in a pile of potentially reusable dust.
For its roughly 15-centimeter-tall prototype node, Arup hired London-based Within Technology Ltd. to define the most efficient theoretical geometry, using topology optimization software.
Galjaard is pleased with the prototype, and she is now working on refining the design to improve production and functionality.
Cost has been "off the scale," says Galjaard, although, in the future, bigger and faster machines should improve the economics. With current technology, it takes up to 15 days to print a node. However, steel printing should be used "if it really adds value," she says.
While Galjaard has focused on product design, her colleagues are skeptical about steel printing for construction. Graham Edge, an Arup associate director, cites as pitfalls doubtful economics, problems in producing suitable powders and a lack of performance data.
"Where we see it used in construction is not necessarily in making components," says Edge, a metallurgist. There is potential, though, in printing expensive mould patterns for sand casting of complicated nodes, he says.
For Edge, the question to ask is, "How can we use this technique to enable us to do some of the things we want to do but, at the moment, can't?"