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+ Robot fills hole in the donut.

SCARA ROBOTS ARE THE COMMON ROBOTIC ARMS USED TO MOVE AND ASSEMBLE PARTS IN FACTORIES. Yet SCARA robots share one big weakness: their work area resembles a donut, with nothing in the middle but dead space. Now Epson Robots says it has developed a new SCARA robot that can reach the middle of the donut. As a result, its new RS3 robot has the same workspace as a robot twice its size.

To appreciate how Epson did this, consider a conventional SCARA robot. SCARA stands for "selective compliance assembly robot arm." In practice, it consists of a two-part jointed arm that moves easily back and forth along the x and y axes, but remains rigid in the z direction.

The upper arm contains a ball screw spline that lowers a tool or gripper to the workpiece. If that arm tries to spin all the way back towards its pedestal, the spline will collide with the base or the lower arm. As a result, it cannot get to the center of the workspace.

The RS3 sets this on its head. First, it is designed to hang from the ceiling, so there is no pedestal in the workspace. What is the upper arm in a conventional installation becomes the lower arm in the ceiling-mounted configuration. "In the RS-3, the entire spline unit is encased beneath the lower arm so it can move freely in the space," said Epson applications engineer John Yett.



As a result, the robot can move freely throughout the entire workspace. This enables an RS3 with a 350-millimeter arm to work on pallets as large as 494 millimeters by 494 millimeters, a size that currently requires a 700 millimeter robot. Smaller robots cost less than larger models, but the real payoff comes from more efficient use of factory floor space, Epson says. Moreover, the robot's 360-degree workspace enables more flexible configurations along the line.

Equally important, since the RS3 can move through previously dead space instead of going around it, it can reduce cycle times for some movement applications by 20 to 25 percent.

Like all SCARA robots, the RS3 provides more flexibility than linear gantry-mounted Cartesian robots. It is also simpler and less costly than more flexible multiaxis robots, and especially when it comes to control. The RS3 comes with Epson's software and RC180 controller, which can be customized to support vision guidance, .Net, and Ethernet, Profibus, and DeviceNet communications.

The company sees potential applications in laboratory automation and other uses that require movement of large quantities of parts to process or testing stations.

This section was edited by Associate Editor Alan S. Brown.

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Title Annotation:Epson Robots
Comment:+ Robot fills hole in the donut.(Epson Robots)
Author:Brown, Alan S.
Publication:Mechanical Engineering-CIME
Geographic Code:1USA
Date:May 1, 2009
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