R&D PULSE
A BETTER
DELTA ROBOT
Additive manufacturing shows promise in creating compliant monolithic mechanisms for Delta robots.
Written by Nancy Kristof
DELTA ROBOTS ARE ONE OF THE MOST STUDIED and widely used parallel manipulators—they’re are often preferred for pick and place operations due to their light structure, high speed, and accuracy. But now, a team of robotics researchers has developed the first-ever Delta robot to be made with additive manufacturing and selective laser sintering, which the team has dubbed Deltaflex.
Delta robots have three actuators on their base, which drive three parallel arms connected to a triangular platform. However, the mechanism’s kinematics limit the platform’s motion to three translational degrees of freedom.
This new work may help to advance designs that maximize the robot’s mechanical strength while reducing the need for support structures. Current compliant mechanisms are highly precise but can be limited in achieving a large range of motion.
“One of the recurring problems is the complexity, putting the pieces together,” said Alberto Parmiggiani of the Centre for Robotics and Intelligent Systems (CRIS) at Fondazione Istituto Italiano di Tecnologia (IIT). Parmiggiani’s team at IIT’s Manufacturing and Design Facility collaborated with colleagues from the University of Genova and University College Cork to explore how monolithic mechanisms can replicate the kinematics of a typical Delta robot. The research offers tradeoffs that designers should consider to help address a robot’s needed range of motion with joint strain, precision, and durability.
“The idea behind the paper was, what if we overcome all these problems by creating a monolithic mechanism,” Parmagianni said. Most previous work in monolithic mechanisms has primarily involved simulations, but the research team was intent on showing how they could work. While Parmigianni’s colleagues at the University of Genova were running simulations for this project, he and his team at IIT were running test 3D prints to optimize the design for stiffness and precision.
“Every couple of days, we would test and experiment one of these new designs,” Parmigianni explained. “We basically combined the submodules together and then ran a test print of the whole system.”
Alberto Parmiggiani, with the Centre for Robotics and Intelligent Systems at Fondazione Istituto Italiano di Tecnologia.
“The idea behind the paper was, what if we overcome all these problems by creating a monolithic mechanism.”
—Alberto Parmiggiani, Fondazione Istituto Italiano di Tecnologia
A delta robot made with additive manufacturing and selective laser sintering, which the team has dubbed Deltaflex.
Credit: Alberto Parmiggiani
Deltaflex is the first application of a monolithic mechanism in a three-degrees-of-freedom robot that replicates the kinematics of a standard robot, he added.
Some of the challenges in optimizing this design included addressing the fact that 3D-printed parts are generally weaker in the build direction, which is where the part’s height increases—typically in the ‘z’ direction. The team had to design the mechanism “to make sure that none of the flexures aligned with the weak direction,” Parmigianni explained.
“It’s got this weird shape. But what that weird shape ends up doing is it allows the robot to move only in the x, y, and z direction,” he continued. The robots were tested for unwanted motions and compared to the desired range of motion, precision, and stiffness, depending on the application.
“You can test the effectiveness of the robot by checking if, while the robot moves, you have unwanted motions, unwanted rotations of the moving end effectors,” Parmigianni said.
Though the project started out as a bit of “academic curiosity,” Parmigianni envisions future work on monolithic structures could address the technology’s use in remote applications, where there may be supply chain issues, or other scenarios where it may be difficult to source components. Other options could include single-use applications such as robotic surgery. To encourage others to explore other such uses, the research team has made all their work open source, including its printable source files.
“We strongly believe that factual science should be as open as possible, and we try and support that whenever we can,” Parmigianni said.
Nancy Kristof is a technology writer in Denver.
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