July 29, 2003/

The Robotic Industries Association (RIA) (Ann Arbor, MI) estimates that approximately 128,000 robots are now being used in the US, second only to Japan in robot use. As the pool of experienced welders dwindles, more companies are moving toward automating the process. Moreover, as American manufacturing moves increasingly overseas to take advantage of cheap labor, the push for higher productivity coupled with consistent accuracy places even greater pressure on the welding industry and on stateside manufacturing at all levels.

The issue may not be should the job shop or metal fabrication shop adopt robotic welding, but when and how. In today's manufacturing environment, automation is becoming a matter of survival.

But for those taking their first tentative steps toward robotic welding, the journey may seem daunting at best. Not everyone needs to automate their welding processes, but as Tim Nacey, general manager, Industrial Group, Panasonic Factory Automation (Elgin, IL), states, "My personal opinion is a lot more people than realize it are candidates for robotic welding."

THINGS TO CONSIDER

But, how do you know when you need robotic welding? For Terry Lacer, vice president of manufacturing for IQL Corp. (Louisville, KY), it was a no-brainer. In the early '90s, IQL was a metal fab shop, doing odd jobs. Sales for the company were around $200,000. But, says Lacer, "We were invited to bid on a $1 million government contract for bulk mail postal carts. Obviously, this was an opportunity for us to grow the company." The problem? There were approximately 4500'' (114 m) of aluminum welding required for each cart. In the beginning, quantities were to start at 20 units per day, though they would later ramp up to about 55 units a day. As Lacer puts it, "That's a lot of weld inches for aluminum." There are those who would argue that it's a lot of weld inches for any material.

However, the point is Lacer had the perfect application for robotic welding. It involved repetitive welding on similar pieces. Also, the firm was already operating at optimum capacity, and had the opportunity to expand its manufacturing capability. It would have been impossible for IQL to obtain the required level of production from existing personnel and technology. These are all reasons to automate.

Nacey believes people need to identify their business situation. The following story explains his point:

"We had a customer that came in three or four times and asked us to weld parts for him so he could do time studies to bid on prospective jobs. When he came in the first time, we were excited for him bidding on a big contract. We called him up, 'I didn't get the contract,' he said. A second opportunity came around, same situation; third opportunity, didn't get the contract. Fourth opportunity arrived and he's back again. Turns out he was bidding with manual labor costs in mind. He thought if he got the contract he could then buy a robot, which would be much faster than a manual welder, and he would make a ton of money. He was missing the point, he never got an order because his price was never good enough. He finally ended up saying, 'I'm just going to buy the d_____ thing. I'll get it up and running and the next time a bid comes in, I will know what I can charge.' So he bought a robot with no project in mind. When he got the next RFQ, he quoted it with the robot. Within three months of buying his first robot, he had to buy a second."

But these aren't the only considerations when determining whether robots would be helpful. Chris Anderson, market segment manager, welding, for Motoman Inc. (West Carrollton, OH) says, "A good rule of thumb is if a company is using six of more manual welders, there is a good chance it has enough work to add a robot. Typically, that means it has some volume associated with what it's doing, which in turn means it's doing sufficient welding and probably welding similar parts."

Dennis Quinn, manager, robotic applications and proposals and Frank Armao, group leader, non-ferrous applications for Lincoln Electric Co. (Cleveland) believe that because of quick changeover tooling and easy robot programming, the number of parts aren't that important anymore. Quinn says, "Before, you would dowl-pin and bolt- down a tool. Today quick-change pins are available." Armao says you can look at robotic welding in two different ways. "You can look at it by saying, 'I can set up a robot to do one job over and over and over.'" For example, Armao was recently at a shop that's going to weld nine jobs a day, 250 days a year, and it's never going to change the robot. "Or," he continues, "as a small fabricator you can say, 'I'm going to use this for whatever parts make the most sense.' Maybe you make 10 different little assemblies on it at various times. Both those scenarios are valid."

Another consideration is the use of high-tech CNC equipment upstream. As Anderson notes, "One of the things that helps smaller manufacturers integrate robotic welding into their operations is the implementation of CNC equipment into their upstream processes They might have a CNC punch, bending equipment, or laser cutter. These give them accurate, repeatable parts for the robotic welding process."

Nacey, too, is a strong believer in the efficacy of CNC equipment in upstream processes, especially lasers. "When considering purchasing a robot, we always talk about repeatable parts. I find more and more small shops have laser equipment. If a shop is laser- cutting parts or has access to laser-cut parts, it is probably an excellent candidate for robotic welding. Incoming-part quality has always been questionable, but the problem may be solved if the shop has a laser or is buying laser-cut parts for dimensional control."

Panasonic has a customer in Cleveland making parts for the military Hummer. "The man," says Nacey, "has a shop about the size of a six-car garage-the kind of place no one would ever look at twice. But in that shop he has a laser cutter, CNC hydraulic press brake, and a robotic welding system. There's no more than two feet (0.6 m) of walkway between the three machines. He laser cuts the material, bends it, and robotically welds it. And, he does all his own programming."

Additional factors that need to be considered include parts to be welded, weld joint accessibility, fixturing requirements, ways to compensate for distortion, and determination of the welding process to be used.

HOW TO GET STARTED

Today's robots can handle a range of welding applications. ABICOR Binzel Corp. (Frederick, MD) recommends that when choosing a robot, the fabricator should consider arm reach and payload, speed and performance limitations, service, and price.

It is recommended that anyone contemplating moving to robotic welding consult with a welding-equipment or robotic-cell supplier, or a welding-systems integrator. IQL, for example, loaded one of the bulk mail carts onto the back of a pickup truck and drove up to Motoman. Lacer says, "There were five basic parts to the carts. With Motoman's assistance, we automated the welding process on three parts. They helped us lay out our fixture tables with two robots working together."

The vendor will help the fabricator evaluate benefits as they relate to costs. As with most equipment purchases, if the vendor is involved right from the part-design phase, it is easier to integrate the welding robot into the entire production process. Decisions have to be reached involving appropriate system accessories, including safety devices; optimal layout of the robotic cell, manpower and training requirements, and service and maintenance requirements. Robot cell lay-out must consider space needs not just for the robot and the fixturing table, but also for the welding power source, robot controller, wire feed package, and for moving the work into and out of the cell.

THE SYSTEMS INTEGRATOR

Just about anyone looking at robotics could use a systems integrator, says Mike Jacobsen, a manager with Genesis Systems Group (Davenport, IA). He believes there are four areas to consider in successfully implementing a robotic welding project. "The first consideration is the parts you want to weld, materials, size, and complexity. Secondly, you have to look at positioner hardware, the robot, and software. Third consideration is the welding process, its parameters, correct equipment, consumables, etc. Fourth is fixturing, the tooling that clamps and holds the parts in place. An integrator pulls all these things together."

FANUC Robotics' ServoTorch wire feeder system eliminates the cost of external wire feeders and provides consistent wire feeding, essential for arc initiation of aluminum wire.

The integrator can help the customer evaluate whether it's a good application. As Jacobsen points out, "As much as robotic integrators hate to admit it, there are applications that just don't fit with robotics." The integrator also evaluates the welding process. "It might be volumes, and/or part fitup," says Jacobsen. "Basically robots are extremely accurate, they operate blind to some degree. You program them where to go and that's where they go. You can use sensors to give them sight so they can adjust. But when you do that, you've added to the complexity and cost, a\nd slowed robot productivity. But the systems integrator helps evaluate all these parameters."

Integrators are not necessarily concerned with particular brand names. The integrator's job is to provide what in his opinion is the best equipment for the required applications. A successful integrator will often offer a broad range of proven robot and component suppliers.

Customers for the systems integrator range from the first-time robot user to the fully automated welding line user. Obviously, first-timers need more direction than the experienced robotic welding user. The systems integrator is usually very good at that, Jacobsen claims.

"The most common mistake made by people looking at robotics for the first time," says Jacobsen, "revolves around the job shop manufacturer who has multiple jobs he's thinking of automating. 'I have one job that's a real pain,' the customer may say. 'I think I'll automate that one.' Now," Jacobsen says, "you have a robot that has a welding problem. Putting a robot on it doesn't necessarily solve the problem."

PROGRAMMING THE ROBOT

The robot doesn't care what the welding power source is doing. But that's why you want the welder or someone who is very capable programming the robot, says Anderson.

As Dennis Quinn puts it, "When it comes to applying the robot to the weldment, we would much prefer to train an experienced welder to run a robot than to take a robot operator and make a welder out of him."

Armao says that most robot programmers are either shop welders that showed some promise and grew up through the ranks or people who went through a two-year engineering technology associates program, or something similar. "What we would like, ideally, is to have one person, maybe the shop's best welder, who has the capability to understand the robot and to learn and handle the programming."

FIXTURING FOR ROBOTIC WELDING

Probably the biggest problem or difficulty in robotic welding is fixturing. As Quinn points out, "Tooling for robots is different than tooling for hard automation or manual welding. In most applications, the robot is in a fixed position. It's like a man whose shoes are nailed to the floor and he has to reach around and try to make welds. You have a fixed position, so it is more difficult to get to certain joints than it would be manually." Frank Armao takes it a step further. "If you're using a robot to make 10 different assemblies, you've got 10 different fixtures. When you put that fixture back in the robot cell, you've got to get it right back in exactly the same spot as you took it out. The robot is stupid. You put the program in and the robot makes the weld and returns to the exact spot it was in originally. If the weld seam isn't there, that's tough, you're going to get a weld there anyway. So," he continues, "in order to put it in the same place every time, you need to make it efficient for small batch runs. You need quick- change tooling. There are several different pin types, such as expanding pins, that can be employed if you're not rotating the part or Ball Lock pins that are used on fixtures that have to be rotated. There are other means, too, of getting the tooling back in the same place. The trick is, when you change out the tooling that you put it back in the exact same place."

Quinn asserts, "The tooling designer should definitely know welding and how to apply it so he allows proper torch access to the joint. Allowing for proper weld wire angle to the joint and push or pull drag angles are critical factors."

But in the final analysis, a robot can not weld just any part that can be welded manually. Clamping requirements, access problems, or specific positioning requirements may make robotic welding impossible or impractical.

BENEFITS

LuK Inc. (Wooster, OH) is an automotive supplier, welding bump shells, impeller shells with the hub on, cover lug welding, and pilot welding. Prasanna Gurumurthy, facilities manager, reports they use robotic welding because their strategy is flexible manufacturing. "Our lines are flexible enough to manufacture anywhere from 225- to 310-mm torque converters. If you look at typically what's done in industry, each product has a dedicated machine or a dedicated line. But we design our machines and our lines to weld anything in the 225- to the 310-mm range."

When changing parts, all that is required is a programming change to the FANUC 4- and 5-axis robots. "All we need to do is go into the robot control and tell it the part number we're changing to. Then we manually change the weld fixtures."

Not only do sizes vary, but weld complexity varies, too. "On the impeller side, we're welding a tube, but on the cover we're also welding lugs and pilots on, and the robot has to go into hard-to- reach areas," Gurumurthy reports.

Another advantage of LuK's robotic setup is that new products can be introduced quickly into existing production. The process can be changed over quickly, resulting in less downtime. And in the high- production environment, Gurumurthy appreciates the accuracy provided by the robots, the weld repeatability combined with higher quality.

For Terry Lacer and IQL, robots opened the door to new business. One of IQL's suppliers told the firm it needed a saw, press brake, and shear to open different markets. "The robots are going to get you in the door," the supplier said, "but you need this other equipment." "At that time," Lacer states, "we were probably 90% welding shop and 90% one customer."

Lacer followed the advice. The firm started doing a lot of work as a second-tier supplier for UPS and FedEx on their material handling equipment. That work, in turn, opened the door to lawn and garden-equipment components.

"The robots got us started," Lacer states. "We had eight guys in the beginning. When we got the robots we jumped to maybe 20 to 25 people, and before the economy went down we were up to 75." Even now, though, IQL has approximately 60 people employed at its facility.

ALUMINUM ROBOTIC WELDING

If you are going to consider robots, you also need to consider alternate materials, particularly aluminum. Today, aluminum is used primarily in the auto industry. It's impact on the Tier Three and lower automotive suppliers is still negligible. But, rest assured, its importance will grow. And even now, there are job shops welding aluminum for industries other than automotive.

Lincoln Electric's Power Wave inverter power sources use ArcLink digital communications protocol, providing real-time process and production monitoring and access to internal data acquisition.

Dennis Quinn points out that five years ago Lincoln Electric would see approximately one aluminum job for every 20 projects for robotic welding evaluation. "Today," he says, "that number is probably one of every eight projects."

But welding aluminum is different from welding steel, bringing it's own set of difficulties. One of the problems, according to Armao, is that aluminum has really high thermal conductivity. "What happens with your typical aluminum weld is that when you strike an arc on the seam, the weld is cold. But as you proceed for more than just an inch or two, the metal warms up and by the time you get to the end of the seam, it's too hot. You end up with a big clump at the beginning of the weld because the part was cold and it didn't flatten out and fuse in well. On the other hand, you have too much penetration at the end of the seam. So controlling that type of thing is one of the issues you have with aluminum that you typically don't have with steel.

"The other thing you'll find is you get less tolerance with aluminum. In steel, you can successfully weld a larger joint gap than you can in aluminum. In steel you can stand a bit more wire mislocation with respect to the seam than in aluminum. In that respect welding aluminum is harder."

"It's harder to get a good-looking start and it's harder to finish off," says Quinn, "especially in a crater area with aluminum. If you don't fill in the crater properly in aluminum applications, there's a greater chance of getting a crater crack as well. It's very difficult to get heat input into the start of the weld, to get it to flatten properly. However, at the finish, because of the robot's ability to change procedures at the end of the weld, and with inverters, it's much easier to control the heat at the crater. We're able to get a good-looking crater fill in almost every case."

Still, the question arises, how does the smaller job shop or fab shop make the transition from steel to aluminum robotic welding. As it turns out, it's not all that difficult. As Panasonic's Nacey puts it, "The robots don't care what metal is being fed through the system, the welding equipment does. If you think you might need flexibility to weld aluminum in the future, you could buy a machine with both steel and aluminum welding capability. If you think about it up front, you might pay another $2000 to get future aluminum capability. Then when you need to go to aluminum, you could pay an additional $2000 and be into aluminum welding. In other words, if the average job-shop guy has an easy-to-do job using 4-mm material with reasonable production rates and expectations, he can upgrade an existing system for a relatively small price."

Remember Terry Lacer and the postal carts? Well, they were aluminum. He admits it did take some time to get going. "When we first started we had difficulty with power sources, with arcing, which is a big problem with aluminum. When we started, we had a lot of stop welds, welds sticking, wires sticking, so we were missing arc generation. We determined that part of the problem was in the power source, part in the feeders. ABICOR Binzel was instrumental in helping us get the correct wire feed system. We were using a push/ pull system, which was what Motoman offered at that time. It took several weeks of troubleshooting and running parts to get it defined, but once we got it going\, we processed 30,000 to 40,000 postal carts over the next six or seven years with the robots running two shifts a day."

Today, Lacer has no aluminum work, so he is working with steel. Now he has a lot of experience working with both materials. In pointing out the differences, Lacer states that obviously you use a different gas mixture. In addition, the wire in aluminum welding is much softer and more pliable. "If you get a bad arc, then the wire can bird-nest back into the feeder very easily. That's one of the reasons you go to a push/pull gun."

Another difference is maintenance. You have to clean your liners. "Since aluminum is softer, if there is dust or other foreign substances on the wire, the feed and liners become plugged, Lacer notes. If the wire's not moving freely through the system, you're going to get a bad arc, you're going to get a bird nest. With steel, you can load a roll of wire and you'll never have a bird nest. You might clean your liners once a week or so. With aluminum, we tried to clean them at least at the beginning of every shift."

NEW DEVELOPMENTS IN ROBOTIC WELDING

One of the problems with robotic welding of aluminum has been the wire feed systems available. FANUC robotics recently introduced its ServoTorch wire feed system, which according to Lincoln's Dennis Quinn is actually a seventh-axis (process axis) servomotor. It is a fully integrated, four-roll wire feeder controlled directly by the ARC Mate series robots. "That means," says Frank Armao, "we can do things with a wire in terms of accelerating and slowing it down and backing it up that we couldn't do before." The control between ServoTorch and the robot is enhanced with ArcLink(TM), the robotic arc-welding network. A co-development with Lincoln Electric, ArcLink provides high-speed control of the arc welding process. It also offers a common user interface through the robot teach pendant, allowing users to select different modes of welding including CV (constant voltage) and pulse welding control.

Dennis Quinn says the big thing on the aluminum side is that with the new power supplies and quicker communications, "We're able to go to lighter-gage aluminum than we ever have before with robots. One of the new modes, pulse-on-pulse, which is really pulse/spray transfer, has enabled us to overcome obstacles. Typically you have to be dead-on a joint, wire directly in the joint. With pulse-on- pulse, we're able to be out of the joint slightly and still make an acceptable weld compared to standard pulse or standard CV."

Chris Anderson believes the biggest thing is digitally controlled welders. "Most manufacturers are releasing products that are applying high-speed processor control to welding machines," he states. "It used to be a welding machine would give you a certain kind of arc characteristic. Even in a pulse machine you would get one particular style of pulse. But with digital welding technology, they can tune a single welder to do several different things. It usually means it can weld thinner materials with better short circuit arc capabilities, or it can do pulse welding-maybe three or four different kinds of pulse shapes or characteristics. The result is more application flexibility. You can do a wider variety of applications.

"As you add more programmability into the welder, ease of use comes into play, which is key," Anderson continues. "For example, you might just plug in 0.045'' (1 mm) wire. You want to pulse and you're using argon/CO2 gas, maybe a 90/10% mixture. The machine will then give you a preprogrammed condition for that pulse program. You don't need to know peak current and all the other parameters. It is done for you."

Motoman recently introduced a robot arm designed specifically for arc welding. "It takes the torch cable and runs it through the arm," says Anderson. Called the "Easy Arc" it features an internal cabling design that provides flexibility and also streamlines the robot profile, allowing access into confined spaces. It improves cable life by reducing wear against the arm, part, or fixture, and also reduces cycle time by minimizing the motion required for torch reorientation.

Panasonic Factory Automation recently introduced a push-pull wire feed system for aluminum MIG welding, which is called MIG Force(TM). During high-speed aluminum welding, 5 m/min in lap welds and 2 m/ min for fillet-lap welds, rapid wire-feed speed occurs at the start and end of every weld. With this system, wire feed speed is controlled at both the start and end of the welds and the arc waveform is synchronized with wire feed speed at both the start and end of welds and while welding.

One component of the system is the push-assist motor, which operates at constant torque that can be set to overcome nearly 100% of natural friction and feeding resistance in the wire delivery system. Reportedly, only 50 grams or less of back pressure is exerted on the wire package by a magnetic, constant torque system, thus requiring minimal pulling force by the planetary gear pull system.

Motoman's Easy Arc welding robot features internal cabling, which improves cable life by reducing wear against the arm, part, or fixture.

This month, Miller Electric Mfg. Co. (Appleton, WI) is introducing a new technology platform they are calling Axcess(TM). Randy Broadwater, the Axcess product manager, says that it puts the welding machine and a computer in the same box. "Basically, all the waveform controls and all the different processes are now software. You can e-mail, download into a Palm Pilot and upload into the welder. Now," he asserts, "you can look at a welding machine as a toolbox. It is full of tools that can be pulled from a robot controller and you can pick the right tool for the job. There's no compromise as far as the limitation of hardware. It's all software now."

It doesn't matter what kind of robot you are using. Broadwater says the controller just tells the power supply to turn on and off or to pull particular programs, depending on the control level already programmed inside the machine. "We're able to put this new technology on older robot systems to improve their productivity. If someone has a five-to 10-year old robot, it's a good way to increase productivity. We've got a technology we call AutoCal(TM) that will calibrate the analog command coming from the robot controller. Therefore, when the robot sends a signal out to give you certain wire feed speeds or voltage, it will give you exactly what the robot asked for, regardless of the robot's age or how off-scale it is."

In essence, the robot and the controller can "talk" to each other. Broadwater explains: "Older robots and most robots on the market today are analog robots, similar to our TV signal, and the technology we're using in Axcess is all digital. We have digital electronics running inside the machine, and we convert that to analog so our machine is compatible with existing robot inventories, as well as a bridge to full digital robots as manufacturers release them. We are one component in a welding cell, there are other components that have to talk with each other, and they are at different levels of the technological development scale. Axcess is capable of participating on that entire scale."

There are two versions of Axcess. There is the machine called Axcess, which is the semiautomatic, handheld machine with a wire feeder for manual, semiautomatic welding. The other is AutoAxcess(TM), which is designed with a completely integrated robot controller.

As the need for even more flexibility increases, it is expected that Axcess will provide it. Broadwater states, "You have a whole host of welding processes in arc transfer modes you can choose. In some applications you may want high deposition and in other applications you may have gaps that need to be filled. There are other applications where you may not be able to get perfect position and need to run it other than flat. You can pick and choose the right tool.

"Materials-aluminum, stainless, and mild steel-are programmed around the most common gas combinations used in the field. There is also the ability, using a standard Palm Pilot and our software, to change wave shapes and to set up every machine in the fleet to run identically."

Broadwater continues: "Axcess is a step in improving what is currently available. While you are welding a joint, if you are going from thick to thin or you get to a place where you have predictable gap, you can switch from one process to the next on the fly while the robot's welding to suit the condition you are trying to solve. Switching between pulse and spray, we have optional Regulated Metal Deposition (RMD(TM)) for gap filling and Accupulse(TM) for higher travel speeds and improved deposition rates. It also features AutoLine where it doesn't matter if you plug the machine in Tokyo and develop your process and methods there and then ship the machine to the US. It will accept any power available anywhere in the world. The machine will run off any power from 190 to 630 volts, AC or DC. It doesn't matter how much of a swing you have, it will give you the same continuous output."

If your shop's welding capacity has reached its limit, or if aluminum welding is looming in your future, or both, maybe it's time to seriously consider robotic welding.

WANT

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SME is sponsoring a two-day seminar on robotic welding. It will be held in Cleveland on September 9 and 10. Call Customer Service at 313-271-1500 for details and registration information.

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