Tube and pipe bending trends

Photo courtesy of Lang Maschinenbau GmbH & Co. KG, Michelstadt, Germany.

To many who have only a little experience in bending tube, the process can be mystifying at best. It often is referred to as a black art, as though it were part science and part voodoo. While bending tube isn't necessarily a mysterious process, it is more challenging than ever before. This puts bender manufacturers in an interesting position, devoting more and more time to dispelling the myths and the mysteries of tube bending while at the same time making it easier to make complex bends successfully.

Despite the difficulties, real or imagined, many bender manufacturers report that tube bending is a hot ticket these days, as growing numbers of fabricators add tube bending to the services they offer.

"Approximately 30 percent of our customers are buying a bender for the first time," said David Wilczynski, vice president of sales and engineering for Pines Manufacturing Inc. Many fabricators who used to specialize in fabricating plate used to purchase bent tube, but many such shops these days are expanding their operations to include tube bending as well.

This is due, in part, to OEM vendor consolidation. Although it's not necessarily a new trend, many large manufacturers are eager to purchase entire assemblies rather than individual components. This trend results in more business going to the fabrication shops that provide the largest variety of processes, so companies that formerly were not involved in bending tube must embrace it or risk losing the business.

For other fabricators, it can be a matter of cutting their reliance on their suppliers. "Many fabricators are sick and tired of relying on other companies' quality and delivery schedules," Wilczynski said.

According to Joe Seibel, president of J&S Machine Inc., lean manufacturing is reinforcing this trend. As large fabrication shops get leaner and leaner, they tend to turn down small jobs that then go to small fabricators that have branched out to add tube bending to the services they provide.

It's an interesting coincidence that more fabricators are venturing into the tube bending industry, while many manufactured components are getting smaller, tube radii are getting tighter, and tube walls are getting thinner. In other words, fabricators with little or no experience are getting started at a time when bending knowledge is more critical than ever before.

Leading the way in increasingly complex tube assemblies is the automotive industry.

"Automotive exhaust systems usually are among the last items to be designed, so little room is left for them," said Fred Burke, president of Lang USA Inc. Consequently, exhaust system designs must have tight radii. Adding to the bending difficulty is the use of thin-wall materials. Automotive component designers are using thinner-wall material than before to reduce automobiles' weight and thereby reduce fuel consumption.

"Exhaust components used to be 1 millimeter thick," said Sabine Neff, general manager for Lang Maschinenbau GmbH & Co. KG. "Now they're thinner, typically 0.8 millimeter thick," she said. Tighter bending radii and thinner walls make successful tube bending more difficult. Lang benders address these concerns by providing a transport boost system that produces boost in the pressure die area. Additional boost reduces wall thinning, decreasing the likelihood that the tube will be damaged in the bending process. Control system accuracy—tightly synchronizing the bending action, pressure die, and transport boost—also helps in successful bending, added Neff.

Although the applications are becoming more complex, programming and operating a bender aren't necessarily becoming more difficult. According to Lang, the controls are becoming easier to use; more fabricators are using electric benders, which tend to be more accurate than hydraulic benders; and the software is always improving.

"We used to have two software designers. Now we have five," Neff said.

David McClew, vice president of sales and marketing for Addison- Mckee, agrees that exhaust tube is getting thinner, and added that tube's role in exhaust systems is expanding.

"More manifolds are made from tubing these days," McClew said. In the past manifolds were more likely to be cast. "Bent tube heats up faster than a casting, so the catalytic converter reacts more quickly," he said.

Exhaust system tubing diameters might get smaller in the future, as vehicle manufacturers use smaller-diameter, and therefore more restrictive, tubing that helps catalytic converters burn more pollutants, according to Barry Kelly, regional sales manager of Eagle Precision Technologies Ltd.

The trend toward smaller components with tighter bends isn't confined to the automotive industry. J&S's Seibel observes that this is part of a general trend in which many manufactured items are becoming smaller and lighter, forcing many fabricators, not just those that make automotive parts, to pack more components into smaller spaces. He also cites replacing traditional steel with stainless steel or metals such as INCONEL® alloys as part of the trend toward thinner-wall components. Such materials are stronger than steel, so their use allows engineers to reduce components' wall thickness without sacrificing strength.

Decreasing the wall thickness also allows manufacturers to reduce material use, thereby combating rising material costs.

Fab Shops and Military Posts

Pines Manufacturing does quite a bit of government business, and it sells many benders that support aircraft repair facilities.

"Our benders have to bend to the tight tolerances required for aircraft," said Pines' Wilczynski.

Although every military branch employs civilians to do some of the work, many times Army or Marine Corps servicemen perform aircraft repairs, so they have to rely on themselves to bend tricky materials such as titanium to aircraft-quality standards. In many cases, they have had minimal training in bending tube.

Eaton Leonard Tooling Inc. is angling for a contract to provide all the bend tooling necessary for the CV-22 Osprey's hydraulic lines, according to Paul Howard, president. In addition to the tooling, the company intends to provide instructions and organization for servicemen in a hurry. All the tooling is stored in a single toolbox, and every box section is labeled with the corresponding die part number and instructions for bend pressures and other relevant settings.

Many bending facilities, either military repair depots or civilian fabrication shops, produce a variety of parts in short runs.

"These companies look for versatility and quick setups," said Audi Lazdinis, sales manager of MiiC America Inc.

For quick changeovers, Eaton Leonard Tooling manufactures reach-adjusted tooling. This tooling is manufactured so that various die combinations share crucial dimensions. After the operator sets up the machine for one tubing size, changing to another size is mainly just a matter of changing the tooling and little is required in adjustments, according to Howard.

Quick tooling changeover isn't the end of it. Ease of programming also helps. MiiC America Inc. emphasizes programming simplicity. "The operator enters bend data using X-Y-Z coordinates and the bender converts this information to bend data," Lazdinis said.

Training plays a crucial role in bending shops today. Vocational programs have been dwindling for decades, and it's increasingly difficult to find trained or experienced employees.

"Factory help is harder to find today than ever before," said Eaton Leonard Tooling's Howard. Many bender manufacturers offer training to their customers.

MiiC America also holds seminars to provide its customers with training in bending and troubleshooting. AddisonMckee provides Bending 101, a course that introduces equipment operators to dies, setups, and other general concepts. It also has a controls class that uses simulated controls that are identical to bender controls and allows operators to create and modify bending programs.

Kelly of Eagle Precision mentioned another important trend—increased use of mandrels. In days past fabricators did quite a bit of empty bending. These days, according to Kelly, nearly everything is bent with a mandrel inside the tube, which is a result of the trend toward lighter material and tighter radii.

Kelly cited two main advantages of using a mandrel: The tube doesn't flatten as it is bent, so exhaust systems have better flow characteristics; and the tube has a better aesthetic appearance, which is good for furniture applications.

Automation and Integration: Today and Tomorrow

The need for automation divides tube fabricators into two camps: Those that need advanced levels of automation for high-volume production, and those that rely on manually loaded machines.

"Some customers need heavy levels of automation, and other customers need less automation and get by with standard hydraulic benders," said Lonnie McGrew, AddisonMckee's vice president of engineering.

"For instance, a 20-foot stick of tube might yield 10 components manufactured on an automated line that does bending and cutting, or a four-tube manifold is manufactured from a single stick in an automated line that uses single-piece flow," said McGrew. "On the other hand, a two-bend application doesn't necessarily need automation," he said.

The need for automation in the automotive industry is especially significant because the pressure to reduce cost is tremendous.

"A fully automated workcell saves man-hours, and this goes straight to bottom-line savings," said MiiC's Lazdinis. He sees strong potential for automation in other industries that don't have the high volumes of parts associated with the automotive industry. Even medium-volume applications benefit from automation, in Lazdinis' view.

George Winton, president of Winton Machine Co., observed that U.S. labor costs are relatively expensive, so manufacturers who want to keep tube bending work in the U.S. must automate. One crucial aspect to automation is management's mindset, according to Winton. If management is comfortable with the status quo, the company is unlikely to automate; if the company is run by movers and shakers, it is likely to automate.

Winton observed that while the bending principles have remained consistent over the decades, the equipment has changed. It is now common to see several operations performed on one machine or transfer lines that transport the tube from machine to machine.

Bender manufacturers have focused on complex bends, compound tooling, and bending short sections, Winton said, and more recently have integrated cutting with bending.

"End formers don't lend themselves to integration as well as tube benders," Winton said. Specialized workcells that perform several processes do exist, though. MiiC's Lazdinis cited automotive workcells that perform bending, end forming, and welding.

"One example is a workcell that makes brake line assemblies that include both rubber hose and steel tubing," Lazdinis said.

Mike Bollheimer, tube bending market segment manager at Wayne Trail Technologies Inc., sees many of the same trends in the seat back fabrication industry. Customers want shorter lead-times on equipment and are looking for machines that not only bend tubes, but can perform a variety of additional functions.

"Manufacturers want complete tubular components processed on one flexible machine," Bollheimer said. "Customers with high-volume programs do not want to load a bender, then load a hole-punching machine, and so on."

Flexible bending equipment loads and singulates a tube; finds and positions the weld seam; executes a bend configuration; end-forms the tube; and utilizes a robot to load a press that has dies that flatten, punch holes, or apply dimples to tubular components.

Bollheimer said customers are driven by the big automakers to have flexible equipment on their floor to eliminate future capital equipment costs. Automakers want to eliminate funding for dedicated equipment.

Winton said he sees more potential for end forming operations integrated with other tube fabrication processes.

"We have some ideas," Winton said. "You'll see things changing soon."

Capabilities such as autoloading and seam finding are on the increase, but it's also important to integrate a bender into the shop structure—not on the shop floor, but in terms of information technology.

"It's increasingly important to integrate tube bender operations into a computer network," Seibel said.

A Look to Tomorrow

The manufacturing trends of the past few years are likely to continue, so tube fabricators can expect to see bending become more complex and challenging. Material price volatility is likely to moderate, but prices aren't expected to fall significantly, so the need for cost reduction and weight savings in manufactured components, especially automotive and aerospace, will continue.

Meanwhile the dwindling of vocational programs over the past few decades and impending large-scale retirements mean that fabricators face a growing shortage of trained and experienced workers.

The state of technology today only hints at what we're likely to see in the near future. Tube and pipe fabricators will rely more on technology—advanced software and equipment automation and integration—as they try to satisfy increasingly complex manufacturing requirements with a work force that has less training and experience than the previous generation of fabricators.