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posted December 19, 2014 09:59 AM
Robots fill the welding gap {url]http://www.robotics.org/content-detail.cfm/Industrial-Robotics-Industry-Insights/Robots-Fill-the-Welding-Gap/content_id/5162[/url]
Manufacturing is sexy. No longer reserved for ops meetings and supplier showboating, behind-the-scenes views of the manufacturing machine are spotlighted in TV commercials, on the Web, and in a brand’s storytelling. One of the reasons – robots. Why? Because robots are sexy.
Jigless arc welding cell with multiple welding robots and two material handling robots to position and hold the parts for processing (Courtesy of Yaskawa Motoman)Shot from the right angle, they artfully demonstrate the advanced technology and craftsmanship that goes into iconic brands. Robots and hot cars are the headliners in a viral video of a Tesla factory tour.
Full-throttle motorcycles also make a great pairing. Kawasaki gave top billing to its chassis-welding robots in a promotional video for the Ninja H2.
Articulated welders are often the scene stealers, complete with their own light show. But beneath the pyrotechnics are advanced metal joining processes. In the future, watch for laser brazing, friction stir welding, aluminum joining, and a new, intuitive kinematic method for programming that will have welding robots snagging more roles.
Robotic Laser Brazing
Highlighted in this video of the Chrysler 200 factory tour is a robotic laser brazing cell. Until recently, this metal joining process was largely kept under wraps. This time the cameras went under the hood, or in this case, up on the roof for a firsthand look.
For several years robotic laser brazing was used on higher-end vehicles. Audi is one example, as highlighted in this article.
“Originally this trend started nearly a decade ago and it started with the luxury vehicles,” says Mark Anderson, Technical Development Manager at Comau Inc., a global automation supplier based in Southfield, Michigan. “The value is now seen across a broad spectrum of car models and makes.”
Anderson describes the laser brazing process and how it’s applied to a vehicle.
“Robotic laser brazing is when we use a laser to melt a silicon bronze filler material into a joint. It’s an aesthetic joint that requires very little finishing or polishing before painting. When done correctly, the two panels joined together almost appear as one. Most laser brazed automotive parts are a roof to body side assembly, or a decklid (trunk lid).”
He says the roof joint is laser brazed for both aesthetic reasons and cost savings. While the initial capital investment for a direct diode laser system is relatively large, the overall cost is reduced by eliminating subsequent operations.
“With a traditional roof ditch that’s spot welded, they generally will spot weld the roof to body side in the ditch and then seal it with an automotive-grade sealer. Then a piece of trim is put into the roof ditch.”
“With laser brazing, you simply apply the silicon bronze (wire) in the joint between the roof and body side, and then use a finishing brush to polish the silicon bronze joint, and basically clean it and paint it. So there’s no sealer, no trim, and you don’t have to worry about trying to schedule production of molded trim pieces that match the color of the vehicle.”
An article describes the process in detail as engineers at General Motors applied the technology in the automaker’s Cadillac division.
“You have a different reason that you go to laser brazing on decklids,” explains Anderson. “With a lot of the hatchback-type vehicles, they want a draw appearance where the rear of the vehicle has more of a bubble look to it. To get the deep draw look, you need to have a two-piece assembly where the upper half of the hatchback will stick out much farther than the lower half. You can’t do that with a single stamped assembly, so they generally braze the upper and lower half together.”
“There are quite a few vehicles on the road now that have gone to a laser-brazed decklid and there seems to be more and more each year,” he adds.
Balancing Speed and Quality
Comau’s Anderson says the integrator’s role is very important when creating a laser brazing solution. Especially since the process requires so many elements and suppliers: the robot, a laser source, the specialized end effector, and the consumables.
Production robotic laser braze system (Courtesy of Comau Inc.)
“When you put all those pieces together, you need to understand the constraints of each one of those pieces of equipment. So for example, when it comes to a laser end effector, we have to specify what spot size we would like to use, which is a combination of fiber optic cable diameter and focus lens.”
“We have to determine if we want to braze in focus or out of focus to meet the customer’s expectations for quality and speed,” continues Anderson. “There are compromises that need to be made in the equipment selection to focus on one or the other. It’s a very careful balance.”
He says any robot that’s capable of moving smoothly across the seam can be used for laser brazing.
“There’s compliance built into the laser braze end effectors, so if there’s variation in the parts or the joint, it’s usually consumed in one way or another in the laser brazing head. It almost acts like a shock absorber. It keeps the laser beam in focus as the head crosses the roof ditch or the decklid. What’s important is that once the robot starts its motion until it completes its motion, it moves smoothly. If there’s any type of vibration, or if the robot has any type of error in its motion path or planning, you will see it in a laser braze.”
Robot end-of-arm tooling for development laser braze system (Courtesy of Comau Inc.)
One of the most critical pieces of equipment is the wire delivery system explains Anderson.
“The wire is where the rubber meets the road. That’s where you’re actually taking something and touching the part. There are quite a few consumables: the wire itself, the wire tips, wire liners and the guide wheels.”
He says Comau works with trusted suppliers such as ABICOR Binzel to ensure the right equipment and consumables for the application.
Flexibility for an Invisible Seam
Robots bring flexible automation to the laser brazing process. Machine vision keeps them true.
“There are many advantages to using a robot for laser brazing versus fixed tooling,” says Anderson. “It’s a very flexible process, where it can handle multiple models in a body shop, from large SUVs to small, compact cars. It reduces the part cost per vehicle. The head on the end effector has several articulating axes that float in the joint to ensure that we’re in focus and properly brazing, even if the parts or the joint varies.”
Robot vision guidance is used in the roof brazing process. Comau’s RecogniSense® system uses a fixed-mounted 2D camera coupled with 3D vision guidance software to guide the laser braze end effector into the roof ditch. For decklid operations, Anderson says the part being brazed is directly coupled to a fixture, so vision guidance is not necessary.
The joint of choice for robotic laser brazing is a coach joint. The benefit is the constant contact between the roof and the body side panel, or the upper and lower half of a decklid. Anderson says it provides a very robust, repeatable joint and ensures good part fit-up.
“A properly brazed roof or decklid almost looks like jewelry when it’s complete,” he adds.
Anderson says right now Comau is focused on the automotive industry for robotic laser brazing. But given his knowledge of the technology, he says it could lend itself to applications in the appliance industry where joint aesthetics are also important.
“There will be more than 15 vehicles launched with laser brazed roofs in 2015,” says Anderson. “That’s across all major OEMs. Laser brazing is here to stay. Over the next few years, I’m positive you’re going to hear about many more systems.”
Friction Stir Welding
Another automated joining process that’s gaining momentum is friction stir welding (FSW). Using frictional heat and forging pressure, FSW creates high-strength joints with a small heat affected zone and minimal mechanical distortion.
Check out a recent video of robotic friction stir welding to see how the technology works.
Touted as a green technology, FSW is lauded for its low energy consumption among other environmentally friendly advantages. This video shows another robot’s perspective.
Aluminum Welding
Friction stir welding is often used to join aluminum, especially aluminum extrusions. Aluminum welding, in general, is a growing trend. More lightweight aluminum is being used in automotive manufacturing, primarily for its fuel economy.
Comau’s Anderson is noticing more aluminum welding using aluminum wire.
“The process is very similar to laser brazing, but it is a welding process because they are melting the parent material, and it is a structural joint,” he says. (One of the differences between brazing and welding is that in the former you don’t melt the base metal.) “They are using it in the same exact roof ditch area. If the vehicle is aluminum, they use aluminum wire (versus silicon bronze for the brazing process). It’s strictly based on whether the vehicle is steel or aluminum.”
Other robot integrators are noticing this trend as well.
“The market is moving toward more aluminum in automotive. Aerospace is another one, but also shipbuilding,” says Ben Woomer, CWI, Application Engineering Manager at Genesis Systems Group, LLC, an automated solutions provider in Davenport, Iowa. “We’re seeing more aluminum applications within the shipbuilding industry. We’re building robotic systems to either weld components for that industry, or systems that could go into the shipbuilding process itself.”
Woomer says most of the aluminum applications in shipbuilding are for gas metal arc welding (GMAW). He notes special considerations when working with aluminum.
“The fit-up is critical and so is having clean base material. Feedability, or being able to feed the wire, is a big part of it. Often with aluminum you use a push-pull gun, so you might have a wire feeder in the back that’s pushing the wire, and out toward the end of the gun, you have a motor that is pulling that soft aluminum wire to help feed it more easily through the torch. On the gas metal arc welding side, the power supply companies have done a lot to really improve their processes and their waveforms relative to aluminum welding.”
He says the advantages include better starts, less spatter and more control over heat input. “It’s easier to do crater fills at the end of the weld,” he adds.
But robots can’t do it alone. They need skilled technicians to program their weld paths. Or do they?
Skilled Welders Scarce
A major challenge facing manufacturers is the burgeoning skills gap and the aging population of skilled tradespeople. Skilled welders, in particular, are in short supply. According to this Bloomberg report, the American Welding Society estimates that by 2020 there will be a shortage of 290,000 welding professionals. Even tougher to come by are welders that can program a robot.
The problem is compounded for contract manufacturers and job shops that typically have smaller lot sizes and more frequent changeovers. In-house welding and robot programming expertise is at a premium.
“The reality of the skills shortage is a big deal,” says Mark Lindquist, President of Rapid-Line Inc., a contract manufacturer in Grand Rapids, Michigan. “We’re not going to find skilled welders coming in the door anymore, where they can just pick up a torch and weld something. Right now, we have five openings for skilled welders and will struggle to find them.”
Robots Fill the Gap
Lindquist says this skilled-trades shortage is one of the reasons his shop deployed robots extensively. The other reason centers around quality. He says it’s “good insurance” because robotic welds are consistent.
“About two-thirds of the world’s office furniture is made within a 50-mile radius. (West Michigan is home to top producers Steelcase, Herman Miller and Haworth.) Our customers are office furniture manufacturers,” explains Lindquist. “They can’t have a person sit in a chair and fall on the floor because a weld broke. So our quality requirements for welds have gone up dramatically.”
“The consistency, repeatability and predictability of a robot weld are far better,” he says. “One robot can handle a lot more work. It may not weld faster than an individual, but the uptime is better. It doesn’t take breaks or debate about the football game. It doesn’t make mistakes or vary the process. You can just run parts through the cell quicker.”
Lindquist says the bulk of their production work was converted to robotic MIG welding. Until recently, robot programming was done in engineering or by a trained programmer on the shop floor. But they only have one skilled robot technician to oversee 11 robots in a shop running multiple shifts, even on the weekends.
“So you’re at the mercy of one person, in our shop anyway, to get all your programs done. A lot of times the programs have to be touched up, for instance when you put the fixture back in, or maybe you didn’t get it lined up right, or the robot has been bumped. You have to go back in and edit the program.”
This creates unnecessary bottlenecks, especially for job shops like Rapid-Line where Lindquist says their average lot size is only 40 pieces. High-mix, low-volume production calls for a flexible solution.
A welder uses an innovative teaching technology to program a robot for MIG welding (Courtesy of Yaskawa Motoman)
Intuitive Robotic Welding Programming
Robot manufacturer Yaskawa Motoman and adaptive gripper innovator Robotiq teamed up to address these challenges with Kinetiq Teaching. An option on Yaskawa welding robots, Kinetiq allows operators to hand-guide the robot to the desired welding positions rather than programming with a teach pendant.
Primarily used for MIG welding, the device itself consists of a force sensor mounted between the robot flange and the welding torch. As you grab the torch and steer it into position, it senses which direction you’re pushing or pulling, calculates a vector, and indicates to the robot which direction to move. A graphical user interface is built into the robot controller.
“With Kinetiq Teaching, we made it easier to program a robot by reducing the time it takes to set up the robot and by making it more intuitive for shop floor personnel,” explains Chris Anderson, Associate Chief Engineer at Yaskawa Motoman in Miamisburg, Ohio. “There are two major components. One is a simplified user interface. The screen looks like a smartphone application. It’s icon-based with a series of pictures. The other component is the direct teaching, or the ability to grab the robot and steer it into the position and orientation that you want to weld. That’s much quicker than using the axis keys to jog the robot into position.”
“We’ve made it more intuitive for a less-skilled programmer to simply position the robot where they want it to go, record that position by touching an icon, and then indicate where they want the weld to turn on and off,” adds Anderson. “Kinetiq Teaching allows you to do smaller batches with quick setup and get the advantage of improved robot quality.”
Faster Setup for Small Batch Runs
Yaskawa introduced its customer Rapid-Line to the patent-pending technology earlier this year. Lindquist describes his company’s experience in this video case study.
“After we installed Kinetiq, we took six of his manual welders and we trained them in half a day,” explains Yaskawa’s Anderson. I showed them how to do a program. Then they did exactly what I did, and they were all able to program the robot within 15 minutes to do a basic program. Then, as they repeated it, one individual got his time down to 5 minutes. So it’s very quick to learn and it’s very quick to get proficient at it.”
Lindquist says programming the traditional way by using the teach pendant to jog the robot to each weld position takes two to three times longer.
“Kinetiq Teaching has been easy to work with,” he says. “Probably a half-hour or an hour of training, and some hands-on practice, and you’re good to go.”
This video demonstrates Kinetiq Teaching versus teach pendant programming the traditional way. Note the time savings.
Yaskawa’s Anderson says that those who know what’s involved in robot programming can easily appreciate how radical a change it is with Kinetiq Teaching. But since 80 percent of welding is still done manually, he says there’s a lot of potential to automate.
“As we take it to tradeshows, we’ve set it up to be a hands-on demonstration,” says Anderson. “The videos help you see how easy it looks. But being able to do it yourself really clinches the deal. We’ve had kids that come in on tours and even they can do it.”
“Generally, once a company buys a robot brand, they fill their plant with that color robot,” adds Anderson. “But some companies have purchased a Motoman brand robot with the Kinetiq device, introducing a different robot brand into their shop just because it’s easier to teach.”
Robotic Welding Integration
Innovations in robot programming are making it easier for small to medium-sized companies to automate their welding processes. Other factors are also putting robotic welding within reach of a broader audience.
“As technology is growing and improving, we’re able to lower the cost, which is opening up the market to smaller industry,” says Genesis’ Woomer. “We really look at the customer and the product they are trying to make, and come up with a solution that makes them successful. By being able to do the tooling and the part program in house, we can deliver a turnkey system to the customer. It takes some of the risk out of automation for the end user and helps them to be successful right out of the gate.”
Genesis Systems Group is an RIA Certified Robot Integrator serving the automotive, rail, agricultural, defense and aerospace industries. Woomer says gas metal arc welding is the integrator’s bread and butter, but they are starting to see more interest in laser welding, especially in the automotive industry.
Dual-robot, three-axis MIG welding cell for an automotive steering component (Courtesy of Genesis Systems Group, LLC)
We explored robotic laser cladding and other laser welding processes in a previous article.
This video courtesy of Genesis Systems Group shows a dual-robot welding cell in action. The Versa RC3L work cell features a center-mounted robot with three axes of motion being used to MIG weld an automotive steering system component. The twin robot configuration helps reduce cycle time.
Welding Robot Simulation
Woomer stresses the importance of tooling, simulation and offline programming in robotic welding integration.
“The tooling aspect is a big deal in automation,” explains Woomer. “You can make a tool that’s not designed for automation, which means you don’t have the torch access that allows you to have the proper gun angles for making a good weld. At Genesis, we have a tooling department with guys who understand what those gun angles need to be and they work with a 3D model of the gun while they are building the tool. Then we use simulation to virtually insert the tool and the part, and move the robot around in the concept stage to get that right before we physically make the tool.”
“It really helps to get the concept on a computer screen, which helps us have a more productive conversation with our customers,” continues Woomer. “Through simulation we can do a proof of concept. Once a project is sold, we use simulation to prove out the design, to prove that the robot can reach everything and make sure that the tooling does leave access the way we thought it would in concept.”
This video shows a simulation demo for a tank welding cell. Woomer says an integral part of simulation is offline programming.
“When we do offline programming in house, we’re able to start that conversation with our customer sooner. So instead of waiting for our system to be designed and for procurement of all materials, and then for our manufacturing group to build the system, we can start the programming early on and have that collaboration with our customer. That conversation is the critical part.”
“There are a lot of ways to program parts,” he continues, “but being able to program them in a way that makes the robot efficient and also accounts for part variation, that’s really important. And being able to add in software tools to accommodate the part variation is also important.”
Design for manufacturing is an ongoing area of focus at Genesis. It involves analyzing the parts intended for welding to determine if they are optimally designed for automation.
“Are there better ways to put a flange on to a part? Is there a better way to do a slip-fit on a joint? Are there better ways in general to do the joint fit-up that allows you to manufacture easier. It’s a big deal,” says Woomer, “because the better you can get joints repeating and have parts in the same location, the less time you have to spend using robot software to correct for those issues.”
“The earlier we can collaborate (in the part design process), the more successful we can make our customers. For example, one of the tools we might use is weld distortion analysis. If we can look at the project early enough, we can put their part into a weld distortion analysis model and figure out how the part will distort. Then we can change our inputs, change our tooling design, or change the design of the part, and rerun that model. It’s all computer-based modeling. It’s something not everyone does, because it’s an investment in the software and knowledge. And you need to do it early enough in the process. You have to be able to still change a part design or change a tool to see the reward from it.”
“With all the technology improvements, someone can go out and buy a robot and a rabbit’s foot and hope it all works out,” says Woomer. “But it’s really an integrator that’s able to make them successful. That’s a key part, being able to pool all that technology, knowledge and experience together to make a solution that’s right for your customer.”
As robotic welding technology continues to bring flexible automation within reach of more manufacturers, their quality, cycle time and ROI will soar to new heights. That’s bodacious automation.
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posted December 19, 2014 09:59 AM
