The Perfect Seam

Pictured here is a laser weld on 0.048-in.-thick EGalv steel. As Amada's Daniel Belz notes, any galvanized material is difficult to weld due to the fumes, and it is prone to porosity, making it an ideal material to laser weld. Image courtesy of Amada America.

Laser welding was originally considered a process that would best be applied in OEMs, where the technology would be used in high-volume, low-mix applications.

However, job shops are finding that investing in laser welding can be effective for them, depending on their product and process mix. By considering your welding work load, your part mix, and the ability of your shop team to work together, you should be able to determine how this technology might benefit you.

Welding Work Load

Dan Belz, FLW product manager for Amada America, noted that if you do a lot of welding in your shop, laser welding should be considered a potential benefit for your operations.

“If between 40 and 80 per cent of the work you are doing is being touched by a welder, then you need to look at the laser welding prospect,” he said. “With the technology you can increase your speed, improve your quality, and eliminate other processes. That is where we are seeing companies finding savings.”

These benefits can be particularly noticeable with jobs done in stainless steel, which can be awkward to weld and requires a good finish on completion.

“We have one customer that had 80 per cent of their parts being touched by a welder,” said Belz. “They build big stainless steel sinks. Their old process was kind of archaic but it worked. They had it down to a science, and they had a lot of good welders. But they also realized that that pool of qualified welders was shrinking. Not everyone wants to weld on an assembly line. They had to consider how to combat that turnover.”

In the case that Belz described, each sink required about 100 in. of weld.

“Typically, the whole process was taking them, start to finish, about 42 minutes,” said Belz. “Now, using the laser welder, it takes them between 12 and 15 minutes. And technically, with the laser welder you can fixture the part, do a dry run of the program, and tweak it before welding. That might sound time-consuming, but in the end it saved about 30 minutes per part on one product, without having to be concerned with scrapping parts.”

Precise Requirements

One of the advantages of laser welding is the ability to construct your setup and do a test run of the welds before starting the actual process. Image courtesy of Amada America.

As intimated above, the heat conduction welding we are discussing here allows a very precise finish on delicate parts and parts that require a clean finish. The laser beam melts the two parts along a common joint. The molten material comes together to solidify and form the weld, which means that there is no concern about the mess that can be created by welding wire used in other forms of welding. Also, with the precise control of the power of the laser, it is possible to properly monitor and adapt to very thin materials.

Although you wouldn’t necessarily choose to replace a bend on a part with a weld, Matt Venuti, mechanical design engineer at TRUMPF, said that in some very special cases, laser welding creates an advantage in this regard because of its precision.

“When you are considering laser welding, you are either aiming to reduce the cost of the part or assembly, or you can keep the costs the same and improve its functionality,” said Venuti. “For instance, you can get an extremely flat and accurate part because you didn’t put a lot of heat into the material by using standard welding techniques.

“If you wanted to make a box with six sides and you wanted it to be as accurate as possible, it would make sense to use six flat pieces of metal and use a complex fixture to laser-weld every seam,” he continued. “That would give you the most accurate box imaginable, and it would be ideal if you were looking for something airtight or watertight with a nice finish. However, if you wanted to make something that was cost-effective and still fairly accurate, you would likely make it out of two parts, introduce some bends, and create a clamshell-like fixture. Then you would be welding half the number of seams.”

Belz noted a customer he worked with that had a high failure rate on finished parts because of warpage that was occurring during the welding process. The 16-gauge material being used benefitted from laser welding because the heat-affected zone was minimal.

“The complexities of parts are so variable,” said Belz. “Our team can often sit down to look at a seemingly simple part and have a 40-minute conversation about the variables we have to consider.”

Laser welding may offer opportunities to add value to a part as well. For instance, Grant Hagedorn, assistant training manager for TRUMPF, said that you can make a very strong structure out of lightweight material by honeycombing the inside of it with metal supports. This can be done with a laser welder because you can weld through the metal to create a weld. Again, the heat-affected area is small.

“That would be almost impossible with traditional welding,” said Hagedorn. “But using laser welding you don’t have to have the traditional joint a traditional weld would require.”

Full Shop Buy-in

Communication is critical in making the change to a laser welding process because it’s often not just a matter of switching from standard welding to a laser welding setup, as we’ve noted in the previous examples. Quite often some redesigns are necessary.

An example of a copper part that has been laser welded. Image courtesy of Amada America.

Belz offered an example of making a box out of 20 thou material.

“It was originally two L’s and a bottom piece,” he explained. “In laser welding, fitment and fixturing are critical, so you can’t use the same fixtures you used for another type of welding process. Because of this, your off-stream preparation has to be done really well to make it efficient. In this particular design, that bottom piece was constantly drifting because of the thickness of the material, so it was difficult to get a good weld on it.”

Belz’ team redesigned the part so that the bottom piece could be formed as a flange rather than a separate piece. With any sort of redesign Belz said, it’s important to have the whole team involved so that the blanking, press brake, and welding team all understand how they can work together to make part processing as efficient as possible.

“Our customers have seen this sort of cooperation growing in their shops,” said Belz. “What I always say is, you’ve got to think outside the box to figure out how you can improve the whole process leading up to welding so that the welding becomes a profit centre instead of a cost centre.”

As Hagedorn pointed out, with the tremendous accuracy that is possible with modern bending equipment, there are a lot of ways to simulate complex bends with offline programming, and the machines are accurate enough to hold tolerances that allow these shapes to be formed.

“If you can eliminate welding completely from the part, you are going to be more cost-efficient,” Hagedorn said. “Or, if it is not possible to eliminate welding, you can start looking at ways to reduce that welding. For instance, if you can bend longer flanges or bends and then weld shorter pieces, that can reduce the cost of the part. In one case, we were able to take a part that had 24 welds and we reduced that to six. The point is, the design that you have been manufacturing for 20 years may no longer apply or be the best fit for the technology available in 2017. You need to invest in rethinking your parts.”

As Belz noted, many design changes may be small tweaks rather than overhauls, but having the whole team work together to determine when an extra bend or one less bend might increase the efficiency of the whole production can make a big difference in overall productivity.

This redesign work may, of course, depend on customer buy-in as well. It may be important to communicate to them the additional value added by using this unique process.

Fixturing Challenges

Although laser welding saves production time in lots of other ways, the fixturing process involved can be a potential bottleneck.

Sample part completed with a laser welder. Images courtesy of Amada America.

“The fixturing costs can be quite substantial,” Hagedorn said. “And the setup time adds to the process. The laser welding itself is a very rapid process, but it’s everything else that adds to the cost because you have to clamp everything in place, run the program, and remove the finished part. That is where the bulk of the costs come from.”

Venuti suggested comparing welding time on the part with the lot size.

“If a typical lot size in a shop is three but it is making lot sizes of this particular part in the 10 to 20 range, then I would consider that a highly produced part,” Venuti explained. “And if that part spends about 90 per cent of its time being manually welded, then likely it is an ideal fit for laser welding. But you need to compare that time with what is required in fixturing as well to make a proper comparison.” It’s also important, of course, to consider the savings realized by not having to carry out any finishing processes such as grinding on the weld.

Your vendor will likely help you work through time studies to break this all down.

“We know that the welding process itself is going to be a lot faster using the laser,” said Belz. “With a small box, the total processing time might be 20 minutes, but the actual welding cycle, with tacking, may be four minutes. The true cycle time, however, will depend on how many parts you can fixture at once, how long it takes to put them in the fixtures, and how much time it takes to shuttle them in and out.”

Laser welding is a substantial capital investment, but approached the right way and with the support of an open-minded production team, it can create substantial benefits as well.

Editor Robert Colman can be reached at rcolman@canadianfabweld.com.

Amada Canada Ltd., 905-676-9610, www.amada.ca

TRUMPF Canada, 905-363-3529, www.us.trumpf.com

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