The New Face of Robotic Welding
Robotic welding becomes a viable option for small and mid-sized shops.
January 24, 2012
Robotic welding systems are more affordable and easier to program than ever before and are thus increasingly attractive to small and midsized shops
Robotic welding, for most people, has become the prime symbol of modern manufacturing. That's because whenever advertisers want to suggest advanced production, they show robot arms doing their rapid dance over auto-body frames as sparks fly.
It's a compelling image, and makes compelling economic logic, too, at least for the large facilities pictured in these ads. Robotic welding applications demand considerable capital outlay and commitment of engineering resources as well; consequently, they generally have not been practical for small and midsized shops. Until now, that is, according to a growing number of robot manufacturers and systems integrators.
Among them is Kuka Robotics Canada Ltd., Toronto. Stephen Rudd, the company's senior applications specialist—welding, believes that it is a misconception that robots are still expensive to purchase and maintain.
"The price of robots has been declining for decades, yet the technology has been improving and robots last longer," said Rudd. "Robots have become very reliable with long service intervals. Major maintenance is an oil change every 20,000 hours, making the cost of ownership low."
Dick Motley, account manager, North American distribution, for Fanuc Robotics America Inc., Rochester Hills, Mich., agreed. Compare the specs in robot company literature now with the numbers from a decade ago, said Motley, and you'll notice that today's robots are overall faster and capable of attaining greater levels of precision and repeatability than their predecessors. The drives, he added, tend to be faster and more accurate, and the motors and motion controllers have been improved.
Likewise, in the matter of reliability—an especially crucial consideration for small and midsized shops—Motley's judgment is aligned with Rudd's.
"Though accurate mean time between failure information can be difficult to obtain, anecdotal evidence is emphatic on this point: Most of today's robots are highly reliable, low-maintenance machines," said Motley.
The new ArcPack Lean 1410 from ABB Robotics, Montreal, is designed specifically for small shops. This newest member of ABB's FlexArc® family of pre-engineered welding cells includes an IRB 1410 robot; ABB's new IRC5 Compact controller; power supply; wire feeder; and a 500-amp, air-cooled welding torch.
Joe Campbell, vice president of the ABB robots and applications group, describes it as an "entry-level, almost turnkey system."
Other robot companies are also striving to sell to what they see as a growing market in smaller shops. Still, no matter what level of capital investment the shop makes, it still has to program the robotic system, and rare is the smaller shop that has an experienced robot programmer on staff. Kuka's Rudd, however, claims that doesn't matter.
Programming Made Easier
"No prior knowledge is required for an operator to run the cell," he stated. "However, a new programmer will require at least a four- to five-day basic robot programming course typically provided by the robot manufacturer. In some more complex applications, an additional four- to five-day advanced robot programming course is recommended."
Rudd described the basic programming procedure this way: "From the home position the robot is jogged to the first position; there may be one or more intermediate positions required to get the torch past tooling and to the weld joint. The welding torch is then oriented on the joint with the correct angles, then the point is recorded. At that position an arc-start command is set."
The pertinent welding parameters are contained within that command. The robot is then jogged to the weld-end position, he said, and the point is recorded again. Within that command, said Rudd, is contained the pertinent arc-end and cratering parameters.
"The robot is moved clear of the tooling, the home position is inserted, and the robot returns home," added Rudd.
Much of the reason that Rudd is so confident that operators can be taught quickly to program a welding robot is that graphical user interface technology for robot programming and control has advanced significantly in recent years.
So much so that Mike Sharpe of Fanuc's materials joining segment feels comfortable in saying, "It is a myth that robots are difficult to program for arc welding. Setting up and teaching a welding program is enhanced with a new, dynamic graphic environment on the robot teach pendant where the operator can view the application data in 3-D."
This technology, Sharpe said, provides images of relevant welding items such as work angle and travel angle, thus allowing the programmer to make intelligent decisions without having to make settings with a text prompt. The new graphical user interface "augments an operator's skill level. It makes welding operations more clear than in the past, where only a text-based teach pendant was used," said Sharpe.
Rudd added that unlike those old teach pendants with their single-line display, today's models have the familiar Windows® look and feel with application-specific drop-down instruction menus and other navigation aids, touchscreens, and configurable application buttons.
"Most teach pendants today provide a larger selection of keys. For example, Kuka Robotics includes a complete QWERTY keyboard, which speeds up typing and overall interaction," said Rudd.
Because of enhancements like these, programming has become a manageable task for the novice and even easier for the experienced welder, sources said.
"Because of the many variables influencing the welding process, a knowledgeable welder is able to learn the programming skills more easily than a nonskilled welder can learn welding skills," said Rudd.
Mention of knowledgeable welders brings up another point. It is sometimes said that experienced, knowledgeable welders and robotic welding systems make a poor match; that bringing the two together interferes with both and makes programming more difficult. A valid observation or the manufacturing equivalent of an urban legend?
"I do not feel that an experienced welder can make it more difficult unless there is resistance to adopting and accepting the robotic technology," Rudd stated. "An experienced welder is able to translate his knowledge of proper welding practices to the robot."
Fanuc's Sharpe is on the same page.
"With the latest advancement in 3-D visualization, a seasoned welder may now easily become a skilled robotics welding programmer," said Sharpe. He added that the newer graphical enhancements improve a seasoned welder's efficiency by easing weld path programming and generally taking much of the guesswork out of the process.
This efficiency is enhanced by offline programming (OLP). With OLP, said Sharpe, "robot utilization is maximized because the robot can run production while a programmer creates and edits offline in the virtual world. However, it does require the robot's parts to be modeled and in the appropriate relationship or calibrated to the robot."
OLP packages typically contain software tools to speed and simplify the calibration process. Most robotics manufacturers have their own OLP software, but generic OLP packages are available as well.
Making Safety Easier
Safety, a previously complex aspect of robotic applications, is still essential, but robot-makers have been working to take much of the complexity out of it.
ABB, for instance, has what it calls "simplified fault management." Normally, a weld error would cause robot operations to come to a halt. The operator would then have to enter the cell to fix the error, and then the system would have to be rechecked and restarted. If a weld error occurs with ABB's pre-engineered FlexArc robotic cell, the robot automatically moves to a service window where the operator can access the welding torch from outside the cell, perhaps to change the contact tip or even check for gas flow.
After maintenance, the operator pushes a button and the robot moves back to where it stopped and restrikes the arc. During this entire operation, the robot can stay in automatic mode, saving valuable production time.
Fanuc has focused on embedding safety functions into software via its Dual Check Safety (DCS) system, which eliminates the need for external limit switches. The benefits, the company says, include savings in floor space, flexibility in system layout, reduced hardware costs, improved reliability, and, perhaps most important for small shops, faster system start-up and easier operation.
Before You Invest
So, robotic welding systems have become relatively affordable and much easier to program than in the past. They boost productivity, typically improve part quality while decreasing part cost, and enhance a company's competitiveness. That still doesn't mean they are right for all shops.
Shops should look at several things before investing in a robotic welding system. First, does the part volume justify such a purchase? Are the parts consistent enough for an automated welding system, or will extra time have to be spent in fixturing and locating the parts? How will the parts be loaded and unloaded, manually or automatically? How does the welding process fit into the overall production process? Would a relatively small investment in additional technology—say, material handling or inspection—significantly enhance the value of the primary robotic welding investment?
Finally, shops should not hesitate to get some help in matters of cost justification. Robot vendors and systems integrators are well-skilled in these matters and can provide valuable help. However, these folks aren't necessarily unbiased observers; peers are good judges about the value of the information they have received from these sources.
Almost Ready
OK, so a shop has purchased, installed, and programmed a robotic welding system and is all set to begin welding, right? Well, not quite. The next step, said Rudd, is to walk the system through the program at slow speed to ensure continuity and collision-free motion paths. After that, the programmer can run the program continuously at a faster speed in teach mode, then at full speed in automatic mode without welding.
"Finally comes full playback with live welding to adjust the process to provide optimum welding parameters and acceptable quality," said Rudd.
Calibration of axes and system components will be required, becauser small inaccuracies can add up to a significant error at the end point where the torch meets the workpiece. Visual inspection is important too. The operator needs to watch out for any unusual, unexpected obstructions, such as manual clamps that were left open and could possibly collide with the robot.
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