Combining inspection techniques to ensure quality tubing

GL Precision Tube runs tight-tolerance ERW product on all three of its tube mills up to 300 FPM. Images: Lincoln Brunner

Sometimes the drive to excel comes from within, and sometimes it comes from your customers. But for the truly ambitious, it comes both ways. tubing mill

That’s where GL Precision Tube in Aurora, Ill., found itself a few months ago when it got wind of a new tool from Xiris Automation that the tubemaker thought might strengthen its position in the market.

For the past year and a half, GL Precision Tube has been using Xiris’ WI-3000 laser profiling inspection system, which inspects for inconsistencies in the edge alignment and the weld bead of electric resistance welded (ERW) tubing rolling off its three mills. (The company plans to restart a fourth soon, according to General Manager Matt Kuhn.) That system also monitors the peak and the freeze line of the weld bead—both of which must be kept within strict tolerances, especially with the thinner wall thicknesses that have become the norm at GL.

Then, at the beginning of this year, the company chose to add another tool: Xiris’ latest technology, the HF-PreWeld system. The system uses Xiris’ XIR-1800, a high-dynamic-range, short-wave infrared thermal camera. This thermal scanning system tracks the temperature of the weld bead and strip edges but also variables like the weld gap on an ERW tube mill.

This latest system also gives GL Precision Tube a tool it had never had before—the ability to track in real time the V angle of the two strip edges being joined. And though GL was the first North American tube manufacturer to install the system, the company bought it for all of its mills at the same time, both because it felt it was an improvement on a competing system it had been using and because of the success it has seen with the WI-3000.

“If we believe that it helps, we want it to be on every mill,” Kuhn said. “We’re not going to shortchange ourselves and not give ourselves the tools that we need to make sure that if we sell it, it stays sold.”

GL manufactures round, square, rectangular, and specialty-shaped mechanical tubing from 5/8 to 3 in. OD in many different wall thicknesses and grades of steel.

The 75-person company, started by Kuhn’s father, Chuck, in 2007, focuses on tight-tolerance tubing that most companies either cannot or choose not to make because of the demanding specifications.

The greatest driver, of course, is weight reduction, which means more high-strength, low-alloy tubes with thinner walls that are 20% to 30% lighter than traditional carbon steel tubing of the same strength. Kuhn said that 12 years ago, if the company ran a batch of HSLA Grade 50 steel, it was a big deal.

“Now I’d say the most common grade we run is HSLA Grade 70,” Kuhn noted. “That’s more or less plain vanilla for us at this point.”

The Xiris systems monitoring GL’s tubing track multiple variables, including the peak and freeze line of the weld bead, the temperature of the bead and strip edges, and the V angle of the strip edges in the weld box.

Consuming about 3,000 tons of steel a month at mill speeds up to 300 FPM, the quality control demands on GL are high. But that rarified space is where the company has found its version of a comfort zone.

“Frankly, that’s where we’ve excelled,” Kuhn said. “That’s where we’ve been able to do a good job, and it’s what’s allowed us to continue to grow, virtually through word of mouth exclusively. We have a very good crew with some good experience, good knowledge.”

The company actually uses five inspection methods on its tube—the laser profiling system, thermal camera inspection, eddy current testing to detect weld flaws, metallurgical analysis of the weld, and regular in-process destructive tests. In fact, on all three of its mills, the company employs dedicated quality technicians whose only job is to do several destructive tests on sample tubes from every slit coil.

The results of the destructive tests are recorded in the company’s ERP system, in perpetuity, to provide 100% traceability on all products. A day’s worth of production on a part will include 50 to 60 destructive tests at minimum. Those tests include a wall-to-wall flattening of the tube with the weld at the 12 o’clock position, one at the 3 o’clock position, a reverse bend, flaring the tube, and piercing the weld. If the first article inspection (FAI) tube passes all of those tests, it can go to polishing and etching. Only after the tubing passes all the FAI and in-process inspections is it then packed and shipped.

All five major pieces are thorough and necessary, but they all have limitations. So, Kuhn and his team decided to invest in this latest thermal inspection tool so that through complementary inspection technologies, they can rest easy knowing that their tubing consistently meets the increasing quality demands of GL’s customers.

“They’re all a piece of the puzzle,” Kuhn said. “With the eddy current and the Xiris systems that we have, I feel like they cover each other’s limitations. In tandem, they give us a high level of confidence, in addition to our destructive testing.

“The customer base that we service, with their demanding applications and expectations, we needed to do everything we could to minimize the possibility of producing and shipping tubing with a bad weld.”

From a quality control standpoint, the goal of real-time feedback on that host of variables is to help tubemakers like GL create and maintain a stable operation, said Cornelius Sawatzky, sales manager for Xiris Automation in Burlington, Ont.

“If we run a stable process, we probably have a good product coming off the mill,” Sawatzky said. “We can set some limits around a nominal working range, and if it moves out of range, it can create an alarm. They can make a little adjustment and instantaneously, they’re back to their nominal position.

“Some of [GL’s] clientele is in the automotive sector, and overall in the automotive sector, the requirements … are very demanding. They’re not very appreciative of any nonconforming material. In the auto sector, it used to be a couple parts per million of nonconformance was kind of your run rate. Nowadays that sector [is] basically saying zero parts per million.”

To satisfy those specs, in addition to its testing tools and methods, the company has adopted what amounts to a companywide quality control culture: Every employee is expected to report a product flaw if they see one. It’s just one more way the company maintains its edge.

“I tell people, ‘Everybody is responsible for quality,’” Kuhn said. “People certainly have responsibilities that they’re keyed towards, but everyone has a responsibility for quality. If you’re walking to the bathroom and you see a tube that got hit by a forklift, the expectation is that you point it out to somebody. We’ve got a good crew. They care. It’s been pivotal for us, and we can’t do anything without a good crew.

“We treat them right. And I think it’s evidenced by the fact that they get their family members or friends jobs [here] because, hopefully, we’re a good place to work. And it ends up being reciprocal. We try to treat them right, and they in turn do what they can to help the company.”

The GL folks don’t pretend to offer the cheapest product on the market—they know they don’t. But with the monitoring and quality controls they’ve put in place, they do aim to provide the best overall value. As Kuhn likes to say, you can’t inspect quality into a part. However, having good inspection devices can and does help control the production process.

“They pay for themselves any number of times, and you never know for sure the problems you have avoided,” Kuhn said. “So, it’s hard to quantify exactly how much it is, but the issues that you don’t have because you have the systems we do, again, is a piece of the puzzle.

“With the market we service being largely automotive or vehicle-related … if they get a foot of tube or a piece of recut tube with a bad weld, they say, ‘OK, prove to me that everything else is good before I use it.’ The only way to test the weld after production is to destroy it, and at that point, after you have destroyed everything, there is nothing left to use. Therefore, the objective is to use all the tools that are available to help ensure weld integrity is never an issue.”

The Tube and Pipe Journal

See More by Lincoln Brunner

Lincoln Brunner is editor of The Tube and Pipe Journal. This is his second stint at TPJ, where he served as an editor for two years before helping launch thefabricator.com as FMA's first web content manager. After that very rewarding experience, he worked for 17 years as an international journalist and communications director in the nonprofit sector. He is a published author and has written extensively about all facets of the metal fabrication industry.