Bridges connect people in so many ways. We can carve a path to family and work, even if our route includes waterways or other obstacles. A 3D printed bridge under construction in Amsterdam brings people together, too, in a project that uses art and technology to produce something that is both functional and beautiful.
“I strongly believe in the future of digital production and local production in the ‘new craft’,” said Joris Laarman, whose Joris Laarman Lab is responsible for the design of the bridge. “This bridge will show how 3D printing finally enters the world of large-scale, functional objects and sustainable materials while allowing unprecedented freedom of form. The symbolism of the bridge is a beautiful metaphor to connect the technology of the future with the old city in a way that brings out the best of both worlds.”
The functional bridge, which is currently being crafted in a warehouse, will be installed across the Oudezijds Achterburgwal canal.
The project is the work of MX3D, a design company that utilizes 3D printing for furniture. Tim Geurtjens, MX3D’s chief technology officer, recently told Product Design and Development that limitations on existing 3D printers led them to create their own machines.
In an early experiment, a used industrial robot was equipped with an extruder head that pushed out a two-part polyurethane resin that hardens in seconds. The method is accelerated by the use of two $10 paint strippers. The robot arm gave the system six degrees of freedom rather than the three degrees afforded by traditional 3D printers. As a result, build volume is only limited by the length of the robot’s arm.
“If you reach the limitation of the robot, you can move the robot,” Geurtjens said.
Geurtjens said that those experiments led to a process uses a standard MIG welder that deposits weld wire instead of plastic. Stainless steel is used for this project with a maximum deposition rate of three to four kilograms per hour. Other MX3D projects using the same welder, however, have utilized aluminum and bronze.
One robot isn’t enough to build the canal-spanning structure. Four IRB 2600 robots, on loan from ABB Robotics, will be used to produce the 500 million to 1 billion separate welds it will take to complete the bridge. These specialized welding robots have wrists suited to grasping welding heads.
MX3D customized the robots with special nozzles and a set of sensors that enable them to closely monitor of the welding process, as well as a custom base that allows them to walk over the portion of the bridge they just created. The position of the robot is determined within the coordinate space of the CAD model, either by triangulated laser range finders or an external laser scanner that images the entire structure.
The robots aren’t the only thing MX3D had to customize for the bridge’s construction. Commercial software was inadequate for driving the robots. Geurtjens said the company developed its own software platform from scratch to integrate the sensors and drive the robots. It uses standard CAD files as its inputs, including Autodesk’s Maya and RHINO formats.
“Ninety percent of what we do is software testing and sampling,” Geurtjens noted.
Safety is a critical issue with a functional bridge, even though the company was able to get around regulatory restrictions governing permanent structures by declaring the bridge a temporary art installation. Even so, Geurtjens said the company is taking measures to make sure anyone walking across the bridge is safe.
The voltage and current profile of every weld is monitored and logged, and a successful weld has a specific signature that will be screened. The company is also looking into thermal imaging to sense whether a surface on the bridge is being heated to the point where it could warp down the line.
In addition, the rate of material build-up is not constant, so the machine uses laser distance sensors to measure the gap between the print nozzle and the piece being created. This provides feedback used to adjust the material feed speed and the robot arm’s work path.
The completed bridge will span 9 meters and will be about 2.5 meters wide, weighing in at about 5,000 kilograms. The only portion of the bridge that will not be printed is the bridge deck, which will be constructed of conventional plates.
Once the design process is perfected in the warehouse, it should take three to four months to print the bridge, but because the project is experimental, MX3D is giving itself seven to eight months. The design and construction process began back in October of 2015.
Amsterdam-based MX3D’s exclusive metal printer has been used in Joris Laarman’s designs before. The first sculptural piece created with the printer was the Dragon Bench. Dragon Benches are now in the permanent collections of the High Museum of Art in Atlanta, the Groninger Museum in the Netherlands, the Houston Museum of Fine Arts, and the National Gallery of Victoria in Melbourne, Australia.
Laarman’s latest artistic collaboration with MX3D is a 2-by-3-meter double-curved butterfly. This piece was displayed at Art Basel in Miami Beach back in June.
The company also collaborated with students from Delft University of Technology to design and create a 3D printed stainless steel bicycle. Students designed the frame in a three-month project. The fully functional bike was street-tested, but its primary purpose is as a concept.
This story originally appeared in our November/December 2016 print issue. You can read the digital edition here.
Filed Under: 3D printing • additive manufacturing • stereolithography, Industrial automation