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Assembly applications are creating more demand for parallel-link machines.
S piders are one of the quickest and most ef ficient assemblers in nature. Just ask anyone who's ever encountered a pesky web blocking a filter, tube, vent line or some other critical artery.
With their spindly arms and extremely fast motion, delta robots resemble spiders. Each ann is driven by a motor mounted in a stationary base above a lar ge cylindrical work envelope. The arm joints work together to drive a rotary axis connected to an end-effector.
Jointed in the middle, the arms bend inward and connect with a small tooling plate to which the end-ef fector is attached. Coordinated movement of the forearms up or do wn pushes the elbows inward or outward, which move the plate in the X, Y and Z axes. As the robot moves up and do wn and side to side, the tooling plate remains parallel with the work surface.
"Mechanically, delta robots are constructed very differently [than other types of robotic conf igurations],'' says Raad Asmaro, account manager for the North American distribution group at FANUC America Corp. "Typically, most robotic arms are considered as serial-link, which relates to having each axis joint mechanically connected in series.
"Deltas are considered to be a parallel-link robot, where the major axes are mechanically connected in parallel," explains Asmaro. "This design provides great motion advantages with explosive speed, accelerations and high duty cycle."
"With delta robots, all the motors are in a stationary location on the mechanism," adds Rick Tallian, picking, packing and palletizing b usiness line manager at ABB Robotics, which first commercialized the technology more than 15 years ago. "Unlike other types of robots, the mechanism does not carry around the weight of the motors. And, the robots operate in an obstruction-free work envelope.
"That, combined with components made out of lightweight materials, such as aluminum a nd carbon-fiber composites, provides a very low inertia system," adds Tallian. "This type of mechanical design allows us to achieve high-speed performance."
Delta robots were originally designed for low-payload applications, such as packaging. That's why the machines are popular in the food processing industry, where they're used to sort and pack everything from fine chocolates to frozen fish sticks. Cosmetic...