Nanyang Technological University (NTU) Singapore said that method of concurrent 3D-printing, known as swarm printing, paves the way for a team of mobile robots to print even bigger structures in future.
The robots 3D-printed a concrete structure measuring 1.86m by 0.46m by 0.13m in eight minutes. It took two days to harden and one week for it to achieve its full strength before it was ready for installation.
The way of getting robots to work together was developed by assistant professor Pham Quang Cuong and his team at the university’s Centre for 3D Printing and a paper was published in the journal Automation in Construction. The NTU scientist was also behind ‘Ikea Bot’, in which two robots assembled an Ikea chair in 8 min 55s earlier.
The new development will allow for concrete designs currently not possible with conventional casting, said NTU. Structures can also be produced on demand and in a much shorter period.
Currently, 3D-printing of large concrete structures requires huge printers that are larger than the printed objects, which is unfeasible since most construction sites have space constraints, pointed out team. Having multiple mobile robots that can 3D-print in sync means large structures such as architectural features and specially-designed facades can be printed anywhere as long as there is enough space for the robots to move around the site.
“We envisioned a team of robots which can be transported to a work site, print large pieces of concrete structures and then move on to the next project once the parts have been printed,” said Pham, who is in NTU’s School of Mechanical & Aerospace Engineering.
“This research builds on the knowledge we have acquired from developing a robot to autonomously assemble an Ikea chair. But this latest project is more complex in terms of planning, execution, and on a much larger scale.” Printing concrete structures concurrently with two mobile robots was a huge challenge, as both robots have to move into place and start printing their parts without colliding into each other. Printing the concrete structure in segments is also not acceptable, it would create joints between the two parts.
This multi-step process starts by having the computer map out the design to be printed and assign a specific part of the printing to a robot. It then uses an algorithm to ensure that each of robot arm will not collide with another during the concurrent printing.
Using precise location positioning, the robots then move into place and print the parts in good alignment, ensuring that the joints between the separate parts are overlapped. The mixing and pumping of the specialised liquid concrete mix have to be blended evenly and synchronised to ensure consistency.
Moving forward, the NTU research team will look at integrating even more robots to print larger structures, optimising printing algorithm for consistent performance and improving the concrete material for faster curing.