Setting up for tube inspection success

The 3D-printed fixtures offered by Mundo-Tech Inc.’s latest venture, Fixtur3D, allows shops to inspect bent tubes quickly and accurately with a modular fixture arrangement.

Some solutions are discovered, and some present themselves. And still others you build as you go, just because you have to. Variable And Attribute

At least that’s what happened at Mundo-Tech Inc. a few years ago when Vice President Chris Harbaugh and his team looked at the choke point in their production stream and asked themselves a simple question: “How can we check this part faster?”

The company, headquartered in Rogers, Ark., bends high-tolerance titanium tubes for a major aerospace defense contractor. For this particular customer, the company fabricates more than 300 different parts, many of them several feet long. The problem wasn’t precise bending, though. Production was bogging down because the inspection process took too long. And when each part has to be inspected with a laser device on a roving arm, the delays tend to stack up.

“I’m trying to streamline everything as best as possible in the shop,” said Harbaugh, whose father, George, founded the company. “After bend, we were having to do 100% inspection. It’s a lot to do—thousands of times. So, we had a lot of bottlenecks because we probably had three benders running and three different people trying to use the rover arm.”

However, instead of looking for a faster inspection system, the team focused on a faster production system. For a solution, they quickly landed on fixturing—specifically creating one on a 3D printer they already had. To test their idea, the team picked an especially tricky bent part that sometimes came up as bad after inspection, even if it was dead-on when measured with a protractor.

It was right then, Harbaugh recalled, that the group’s collective wheels started to turn, and they began asking more questions—the kinds of questions that get answered not by ideas, but with actual things that you can measure and touch:

“We actually ended up running that set of parts though there pretty quickly,” Harbaugh said. That quickness was the result of simply using the fixture to revamp Mundo-Tech’s production process in a simple yet profound way—placing fixtures for inspecting tubes at the bender. Tubes come off the bending machine and get inspected immediately as the next tube is being bent.

That one tweak in the flow has resulted in what Harbaugh estimated is “at minimum a 25% productivity improvement” in Mundo-Tech’s bending operations. That means time and material savings on each part.

“You’re reducing scrap because you’re not waiting until you get all the parts bent and then go off to inspection,” Harbaugh said. “Five are wrong, then you go back and set up the machine again to make five more. So, we’re making sure that the full part quantity we’re making is good before it leaves the bend area.”

And as for trimming, once the tolerances and witness lines are marked on the fixture, operators can quickly scribe bent tubes, trim them, and then place them back into the fixtures for inspection.

(From left) Brothers Joseph Harbaugh (director of sales), Chris Harbaugh (vice president), and Mundo Harbaugh (president) run Mundo-Tech Inc. and Fixtur3D.

“So, instead of waiting for quality to come by and inspect all the parts, these gauges are allowing the operators to keep quality on the floor, keep quality in each phase,” Harbaugh said. “They’re go/no-go gauges. That’s really part of the key. They’re going to fit or they’re not going to fit.”

The new fixtures and the new production process they’ve birthed made so much sense for Mundo-Tech that the company quickly printed new fixtures for all 300 aircraft parts it fabricates for its aerospace customers.

It worked so well that Mundo-Tech created a brand-new business, Fixtur3D, about a year ago to take advantage of the success it had experienced in-house.

That expansion into all those parts, a large portion of which are longer than the 12-in. limit on the 3D printers, meant creating a way to use two or more fixtures in tandem to secure the longer pieces in its part catalogue, many of which are 2 to 3 ft. long.

Arranging fixtures together necessitated a different mode of mounting them. The team at Mundo-Tech and Fixture3D landed on a standard pegboard onto which plastic or metal fixtures of virtually any shape, configuration, and number could be fastened. With that system, the sizes and types of parts that could be accommodated multiplied exponentially.

“We start off with a loaner,” Harbaugh explained. “We send the pegboard out—right now, we have four different customers that we sent the pegboard to—and as they need a new fixture, we’ll design it and prove it out here on our pegboard, which is identical. So, when they get it, they know it’s going to fit 100%.”

One such customer is Trane Technologies in Tyler, Texas. The facility fabricates copper tubing for cooling systems, creating the subassemblies for chiller units on their way to the assembly line.

Trane approached Fixtur3D at last year’s FABTECH show looking for a way to simplify the fixtures it uses in its brazing operation for the copper tubing.

Specifically, Trane wanted smaller fixtures that could help it save space compared to the space demanded by the 2,000 to 3,000 aluminum fixtures it currently uses. In addition, it wanted to reduce the number of injuries workers have suffered moving those aluminum plates throughout the plant.

The company also wanted fixtures that allow air to flow through them (for cooling) and affix to an articulating table that could rotate to facilitate 100% downflow brazes, thereby maximizing both gravity and the capillary action of the silver alloy brazing material.

Fixtur3D prints its fixtures from standard PLA material but also metal, such as 316 stainless.

Fixtur3D delivered a stainless steel modular fixture that withstood drop tests onto concrete from heights of 20 ft. and experienced minimal heat transfer, even when subjected to brazing torch temperatures exceeding 2,000 degrees F. That’s critically important to protect the seals inside many of the valves that are part of the subassemblies being mounted in the fixtures.

“They didn’t shatter, didn’t break, so they’re going to be a really robust product for us moving forward,” said an impressed P.J. Zaccagnino, unit manager for fabrication at the Tyler facility. “We’re not easy on any of our fixtures. Our tooling here, we’re constantly fixing and rebuilding it. So, it was cool to see that.

“The other wonderful thing is the lack of heat transfer in the actual fixtures. We did the probe on the fixture right next to the column that we basically had been lighting on fire for almost a minute. It was only 280 degrees.”

Because Trane has been working with Fixtur3D for less than a year, Zaccagnino said his company is still in the research and development phase of figuring out how best to use the fixtures. However, he and his team like the possibilities and what they’ve seen so far, especially the potential floor space savings inside the plant.

“It’s a lot easier and much better storage for our fixtures,” Zaccagnino said of Fixtur3D’s modular system. “We’re able to reduce that floor space just by our inventory. And, we haven’t dived completely into it, but we’re looking at how we can make some universal fixtures, which then also would cut down on the number of fixtures required.

“A lot of the cool part is, our minds are just going wild with all of the ideas of what we can do,” he said. “It’s been hard to kind of narrow it down, what we want to tackle first, just because there are so many creative ways with the 3D printing that you can come up with a solution.”

Fixtur3D seems to look forward to the challenge of branching out as widely as its customers want to—with legacy aircraft or automotive parts, for example.

“I think there’s a great space, with our background of engineering in tubing over 30-something years,” Harbaugh said. “[What] we’re able to do is take some of that legacy data or even samples and reverse-engineer that to deliver 3D models of the tubes and then the appropriate fixtures. That can technically be printed on demand if we have the right database for fixtures for legacy aircraft.”

The pegboard mounting offered by Mundo-Tech and Fixtur3D accommodates multiple sizes and configurations for pieces up to 3 ft. long or even more.

The Tube & Pipe Journal

See More by Lincoln Brunner

Lincoln Brunner is editor of The Tube & 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.