Robotic Welding: Assessing Options
- April 28, 2019
Today’s robotic welding systems are easily integrated, but it’s choosing the right equipment that is the tricky part
Getting into the automation game isn’t as daunting as it was 10 or 20 years ago. Today’s workforce is far more tech savvy, but for job shops looking to automate welding processes, the consideration is twofold: a dwindling skilled workforce and the need for quality welds on a consistent, repeatable level.
In the early days of robotic welding technology, many companies rushed into such an investment and had a bad experience—either they were unable to dial-in the parameters or they just weren’t getting the end result they had expected. Unfortunately, that meant those robotic cells sat idle or were abandoned altogether. A lot has changed. The once complex operating systems have become more sophisticated with simpler front ends, making them easily integrated and user friendly. And, of course, the cost of the equipment has come down.
According to experts, one common mistake many companies make is how they go about choosing the right equipment. “It’s a very simple rule: crawl, walk, run,” says Kevin Summers, senior automation sales specialist and welding engineer for Miller Electric. “Software is easy to add, but the hardware is more difficult. If you know in the future that you’re going to have a bigger part that might require secondary positioning, for example, it doesn’t make sense to start out with a flat table system. You need to plan ahead and invest in a system that you can grow into. Where you want to go is just as important as where you’re starting.”
Summers adds that if future growth or increasing productivity are some of the key drivers, it makes sense to invest a little more and get a system that has a bigger capacity. “But always apply the 80/20 rule. You want a system that will handle 80 per cent of what comes through the door—the bread and butter—while understanding that there may be 20 per cent of big applications that will never sit on the robot.”
Nick McDonald, ABB’s business line manager, welding and cutting, robotics and applications advises to “take on the easier applications or the lower hanging fruit right off the bat. You want to start with a win.
“Too often we will walk through a plant that doesn’t have any automation or limited automation and we see applications that would be well suited for robotic welding, but they walk us past all of those and take use to their most difficult application. And that’s where they want to start,” says McDonald. “The idea is if they can do the most difficult process, they can do everything. Sometimes doing the hard job first can sour any future automation that would be successful. It doesn’t always make sense.”
When selecting equipment, it’s essential to include the right people who know the welding applications in the decision making process. “We met with a company recently that did exactly that,” says McDonald. “They brought in their engineering manager and plant manager, the two people that were going to be responsible for the equipment. And we got excellent feedback on the end product and how the product is welded.”
Compared to manual processes, the arc on time goes up by 85 to 90 per cent with semi-automated or automated robotic cells. The time it would take a welder to position him or herself, stopping the arc and turning it on again, or just positioning the part, pretty much gets eliminated. That said, a skilled welder is still required to set the parameters and make any needed adjustments on the fly.
“When we automate, some skilled welders that enjoy the process really get into the robot,” says McDonald. “They can do what they wouldn’t have been able to by hand or they may have spent five years developing a particular skill that they can then teach the robot to do with the right equipment. And you’re taking the best weld that can be done by hand and having the robot do it, repeatedly and consistently, while the operator can still make tiny adjustments. So really, you’re taking your highest quality weld on your welder’s best day and improving it.”
And because the robot is 100 per cent repeatable, you don’t need skilled workers to load or offload the parts. Once the welder programs the cell—inputting parameters such as the tip to work distance, work angle, torch angle, travel speed and wire feed speed—the robot will do exactly what it’s asked. “Once that’s done, that highly skilled worker can program another robot or take on other projects,” says Summers.
Growing with the flow
For small to medium job shops, flexibility and repeatability are essential, and shop floor space is at a premium. It’s important to consider the flow of the process and how the equipment will be used.
“Square footage of plants can be very expensive. We are always talking to customers about that when they’re looking at new machines and choosing the right one,” says Andrew Newman, Fronius’ robotic weld senior applications technician. “We have a welding process called CMT (Cold Metal Transfer) Twin welding system that can weld three times faster than a single weld or single wire welding process. Being able to weld faster can potentially eliminate three robots from a welding cell. And what you get is a reduced footprint and increased throughput.”
Newman says Fronius took its single wire CMT process and adapted it to the Twin system. This allows higher heat input on the front arc and lower heat on the back arc, which translates into faster welding speeds and increased control of the arc.
The advantage of twin-wire style welding solutions is the ability to improve productivity dramatically. For instance, Lincoln Electric has introduced a new patent pending twin wire GMAC welding solution for semi-automatic or robotic applications called HyperFill. According to the company, the technology increases the usable deposition rate by an average of 50 per cent when compared to traditional single wire GMAW and delivers excellent weld quality and puddle stability.
Many suppliers offer pre-engineered welding cells that are ready to be programmed right off the delivery truck. Lincoln Electric’s Fab-Pak FT is a pre-engineered robotic automation cell that features a dual zone system for welding small parts and is built as one piece for easy installation and portability.
Depending on production needs, these welding units increase in size and capabilities to offer secondary positioning or external axis if a part needs to be rotated or repositioned, for example. And they can be easily relocated depending where the needs are on the shop floor.
“You can get significant output for a very small footprint with these robot systems,” says Summers. “But again, depending on what your flow is, you may choose a ferris wheel style system that allows you to position the robot against a wall or in a corner in order to maximize space. Or you may choose a side-by-side configuration because you want to run different parts on different sides to be able to accommodate a higher mix of parts coming in.”
Most job shops deal with high mix, low volume orders. And with the software available on these units, once a part is programmed, it’s as easy as calling up the file and pressing start.
There are also software options to monitor your welding output. “You can set a threshold limit—minimum and maximum values—and if for some reason the gas supply runs out and the welding voltage is abnormal, the system can sense that and shut down so it doesn’t continue to make bad parts. You can choose within the software functions how you want to monitor the weld, such as a warning that it went outside of the process, or you can have it completely shut down until someone verifies or validates what’s been done,” says Summers.
To further help ease operation, there are a number of peripherals and add-on technologies. Fronius’ FlexTrack line offers an arc current control (ACC).
“This allows you to have an automatic torch height adjustment. It reads the current and will adjust the height of the torch if there are any variations in the parts geometry,” says Newman.
For ABB’s robotic welding systems, there are some essential tools that will help keep the process running smoothly day in and day out. “With the robot running constantly, you may not realize that the torch is in bad shape,” says McDonald. “So having a torch cleaning station is an absolute must.”
Another tool ABB recommends is its BullsEye—a tool centre point calibration system. If a torch is banged or bent, then everything about your program will be off. The BullsEye automatically corrects damaged or misaligned tools.
McDonald explains that it uses a laser beam to locate where the tip of the torch is and where the stick out should be. “The robot will take the torch and break this beam a number of times, on a number of different angles. Every time it breaks this beam, it records where the robot is and compares that to where it thinks it is. If they’re different, it will flag it and notify the operator that the torch is off by five millimeters, for example.
“This prevents you from having to reteach all your programs,” says McDonald. “If you have to reteach that torch point, it can take up to 10 minutes if you’re good or a half an hour if you’re not.”
And while manufacturers do their best to make all torches the same, they’re never exactly the same. “If I put a new torch on, I know it’s going to be off by a couple of millimeters. It would be a mistake to put a new one on and hit start. It’s not going to be the same as the last one, especially if it was four years old and banged around.”
ABB also offers thru-arc tracking called WeldGuide IV that measures inside a weave and determines where the centre of the joint is based on current and voltage. If you’re welding a long seam on a tank and it moves a little, this sensory guide will track it.
“And we also have tactile sensing where you can use the wire or the cup of the nozzle to determine where the actual part is and record its position. This can also be done with a non-contact laser, such as SmarTac Laser,” adds McDonald.
Knowing where you should start with robotic welding processes, where you want to be in the future, and choosing the right equipment for your operation is crucial. Summers says that you want to manage this new technology that you’re bringing into your shop in a way that pays off the investment and builds a history of success with employees and management.
McDonald agrees. “The right torch can make a difference in terms of success. For repeatability, a high accuracy robot is important. But having the right equipment and the right people is just as important, and this is coming from a robot guy.” SMT