Advances in Robotics Continue to Improve Assembly Speeds

by: Richard Mandel

In terms of a historical scale of machines in manufacturing, industrial robots have barely reached the crawling stage. Simpler functions, like the repetitive movement of an object from point a to point b or the welding of a series of spots on a frame, are easily accomplished with any of a vast array of machines. But changes and improvements in software and hardware are paving the way for industrial robots to be applied to a wider range of tasks.

Stäubli Faverges, Faverges, France, is a robotics company created in 1988 when Stäubli Corporation purchased Unimatics from Westinghouse. They have been producing the RX series of six-axis robots since 1992, for industries ranging from ceramics and glass to electronics, automotive and aerospace. Experience gained from their production of specialty couplings and machines for the textile industry has enabled them to provide unique solutions and improvements to assembly line functions.

Many hands make light work

A work cell developed at German lighting fixture manufacturer BJB uses 13 of Stäubli's robots -- ten RX 130s and three RX 130Ls. Designed to wire and assemble lamp ballasts, fuse holders and electrical supply terminals, the ADS automated components assembly cell combines flexibility, modularity and efficiency.

After redesigning components for direct wiring in which wires are clamped or crimped rather than held with screws or riveted fasteners, BJB took a look at its assembly process. With the goal of improving its material handling and assembly processes, the company opted for an automated line.

"We chose Stäubli robots because they are user-friendly," said Karl Friedrich Kämper, BJB's head of automation. "They have rapid reaction times and they come with powerful yet flexible software."

The thirteen 6-axis robots work like industrial weaver birds, taking wire from spools and cutting them to length, then assembling the cut lengths to the lighting components. Wires can be held by the robots horizontally, vertically, or at a 90-degree angle. After automated testing, the finished subassemblies are sent by conveyor to the lamp assembly lines.

Components that were previously difficult to wire manually by an operator present no problem for the robots, which are able to articulate in ways not possible for humans. The reach of the RX 130 is 1360mm, with a repeatability of ±0.03mm; that of the "L" model is 1660mm, with repeatability of ±0.035mm. Wiring of the fixtures is accomplished at high speeds, even where wires pass within restricted spaces.

Thanks to the introduction of the robotic line, BJB has reduced production costs and improved the quality of its products, while enhancing its ability to offer both standard and custom lighting products. The lighting company is currently looking at the possibility of developing linear component assembly automation.

Many-tasking hands help, too

This year, Stäubli introduced the MPS 360 tool changer system. The unit permits a single robot arm to couple to more than a half dozen different tools, with full connection for energy, data and fluid requirements, automatically and untended. The use of the system can reduce assembly line lengths as individual robots handle a series of diverse tasks, instead of single functions, such as riveting and welding on an automotive assembly line. Malfunctioning tools can also be changed out with virtually no downtime.

The low-impact coupling is operated by shop air, sliding a taper between caged balls to force them to grasp and lock on the tool. Using this design permits a small amount of "play" when the robot portion slips over the tool portion of the coupling, but then the balls create the correct alignment and a positive lock once connection is made. An added mechanical safety lock prevents accidents in the event of power loss. The changer can support up to a 360kg load, with a maximum acceleration of 50 m/s². Flush-face, clean-break couplings can handle cooling water or air at pressures up to 16 bar, and the connectors for welding will handle up to 150A at 630V. Connectors for motive hydraulic fluids can tolerate up to 3000 psi. The unit has space for fluid couplings and electrical connectors for up to five modules, providing the equivalent of five individual robots in a single zone.

The tool parking system employs a single, double-tined fork on a stand. Cantilevering the fork provides clearance for most tool configurations, and the non-tripod design of the stand further reduces the dedicated floor space necessary for tooling in a production cell.

For more information, contact Stäubli Corporation, PO Box 189, Duncan, SC 29334. 800-682-7362. http://www.staubli.com Circle 440.