A Delta robot picks and places confectionary treats with speed and accuracy, for higher throughput.

Peter Gschwender
alpha gear drives
Siegfried Wallauer
Wittenstein Motion Control
Bartlett, Ill.

The packaging industry's most successful rapid transfer robot — the Delta robot — was developed in Switzerland during the early 1980s by Reymond Clavel. Since then, this lightning-quick, spiderlike mechanism has spread to factories around the world, proliferating in packaging, medical, and pharmaceutical applications. Their forte is pick-and-place, where they are often deployed in pods of up to 20 synchronized systems that collectively handle 100 to 2,500 products per minute.

The need for productivity that spawned the development of Delta robots also drives the ongoing efforts to refine them. No matter how well they operate in terms of speed, accuracy, reliability, and uptime, it's never enough. As a result, robot builders are continually looking for ways to improve their designs and optimize components to meet tomorrow's ever more demanding needs. Not surprisingly, those who follow the interdisciplinary (mechatronic) upgrade path are finding success, especially when they focus on the torque-producing elements, servomotors and gears.

Delta details

The Delta robot is outlined in U.S. patent No. 4,976,582. As Delta-related patents continue to expire, available controls and mechanicals will proliferate.

The basic geometric concept behind the "Delta" parallel robot design is the use of parallelograms. A parallelogram allows an output link to remain at a fixed point of reference with respect to an input link. By using three such parallelograms, the orientation of the mobile platform is completely restrained, so that the robot offers three translational (and one rotational) degrees of freedom. Input links of the three parallelograms are mounted on rotating levers using revolute joints.

The revolute joints of these rotating levers can be actuated in two different ways, using either rotational ac or dc servomotors or linear actuators. What makes the Delta design ideal for pick-and-place applications is the robot's fourth leg, which is used to transmit rotary motion from the base to an end-effector mounted on the mobile platform.