Robots go Hollywood: today's welding robots take center stage the manufacturing floor

Gases & Welding Distributor, July-August, 2004 by Chris Anderson

As welding robots have become more economical, productive, and reliable, their use has expanded from automobile assembly plants into small jobshops. But sometimes it takes an outsider to manufacturing to show just how far robotic-welding technology has come in recent years.

For example, two Motoman UP-series robots looked at home in the action film "Paycheck" starring Ben Affleck and Uma Thurman. Originally, the Motoman robots were slated to be in the background of the $5 million high-tech biosphere laboratory set, but after the film's director, John Woo, saw their speed and capabilities, the two robots were given action roles, even interacting with Ben Affleck and other actors in several key scenes.

To the movie's director, the robot's speed and motion translates to visual excitement. To manufacturers, this speed translates into more parts/hr and higher profits.

The movie's crew was surprised how quickly and easily they could create and edit the robot programs. They were familiar with programmable-motion carriages used for panning movie cameras, but these require a couple of hours to implement even simple changes. On the movie set, the Motoman technician developed several programs choices in a matter of minutes, letting the director pick the version he liked. The technician made minor program changes in a few seconds right before the movie crew's eyes.

The crew also found the robots economical. While cars, houses, and even welding power sources have increased in price, robot prices have dropped. Today, shops can purchase a welding cell--a robot, positioner, and safeguarding--for about the same price as a bare robot in the early to mid-1980s.

Beyond the movie set

The Hollywood crowd was impressed, but what about manufacturers exploring robotic automation? They want easy-to-program systems that offer the performance necessary to boost productivity and benefit their bottom lines.

The Motoman robots used in "Paycheck" were six-axis UP-50 and UP-20 models, both with the lightweight XRC controller. The screen on the programming pendant is a backlit monochrome display that uses icons and text to relay information to users. Today, Motoman offers a more-advanced control, the NX100, which it introduced at the 2004 AWS show, along with the EA1400N robot manipulator.

The NX100 robot controller keeps the light weight and ergonomic-friendly pendant used on the XRC, but adds a larger, color touchscreen display. Programmers simply touch a menu button to display more information, or they use cursor keys on the pendant.

The unit displays programs in Motoman's Inform language, which has been part of the last three generations of controllers (XRC, MRC, and ERC). This makes it easy for plant personnel to learn the NX100 controller and the new features Inform III offers. Users can save the Inform programs from the controller and display/edit them from a computer with any text-editing program.

Learning to program is relatively easy--almost anyone can learn the basics. Half of the keys on the pendant are motion related, letting programmers move robots to desired positions with particular orientations. However, Motoman recommends companies send welders to the one-week training class to learn how to program the robots.

The robots also make use of the skills of experienced welders, who know what torch angles to use and how other parameters effect welds. Hence, the robot software can interpolate motion between points to move in a straight line (linear motion) or in an arc (circular motion). The programmer can then enter an exact speed for the tool centerpoint (TCP), which is normally defined as the end of the weld wire.

Using interpolated motion, a programmer normally just records points where a weld starts and ends, and the robot calculates the weld path. Programmers insert points between welds to ensure the robot moves around parts and tooling.

Pendant keys let programmers step forward and backward through programs to see if robot paths are correct and won't crash into anything. If there are problems, they can add instructions to the program to start or end an arc, turn on an output, wait for an input from a device, or call another program. Such instructions include provisions to enter desired amperages and voltages for particular welds.

The NX100 expands the XRC's capability to control up to four robots. All four programs can run at the same time with each robot operating independently. Anticollision software ensures the robots won't run into each other.

A Tier-one automotive supplier in Canada uses a large Motoman robot to handle a part while two process robots arc weld it. With only four cells using robots as flexible part positioners, the manufacturer matches the throughput of six traditional robot cells with positioners. This approach reduces capital costs and provides tremendous flexibility for future part changes requiring change of only the robot grippers.

The XRC's built-in PLC functions let it control more than just robot motion. For instance, it has up to 10,000-line program capability and allows drag-and-drop ladder programming. In monitoring mode, the pendant highlights true logic in red, which greatly simplifies troubleshooting. Eliminating the need for a PLC to control tooling and conveyors also reduces system cost and complexity.