An employee places pre-bent tubes in a hydroforming press which will fill the tubes with water, forcing them to conform to the shape of the mold.

Manufacturers often use 3D measurement data to verify features on complex parts, ensuring that the finished component meets standards to exacting degrees. At American Hydroformers Inc. (AHI) in Fort Wayne, Indiana, engineers did just that, but they got even more value out of the system on the early end of their manufacturing processes, before more precise forming operations took place.

The shop produces safety-critical components for automotive frames and other structural parts. Employees fit bent tubes into complex dies, fill the steel or aluminum tubes with water, and dial up the pressure until the steel conforms to the shape of the die, creating the net-shape part. This tube hydroforming technique, growing in popularity with automakers for decades, handles complex materials and creates lighter, more consistent parts than stamping and welding.

General Manager Mark Blasi says with orders increasing at AHI, the process bottleneck wasn’t coming from the hydroforming process, it was coming from CNC tube bending.

“Tooling wears on those, mandrel walls wear out,” Blasi says. “You have to have the same shape to within a millimeter or so, because if you don’t, the part doesn’t fit the die. You’d have parts that were coming out of the die where you didn’t want, so as the die closes, it would skive the part a little bit. You’d end up with pinches in the die as well as parts that wouldn’t pass final quality control.”

Until about a year ago, AHI employees used mechanical gages to check tube accuracy before placing parts into the hydroforming die. The gages required employees to place bent tubes into a nest, and the part would only fit properly if the tube’s dimensions were in spec. In practice, Blasi says, it was too subjective. Depending on how people put the tubes in the fixtures, one person could get it to pass while another would consider it a failed part.

An engineer uses a Faro ScanArm for contact and non-contact measurement of a complex 3D part.

To solve the in-process part-checking problem and to validate prototypes for other AHI work, Blasi chose to invest in a Faro Edge ScanArm HD, a portable 3D measurement system with attachable laser scanner for both tactile probing and non-contact 3D scanning, that can quickly generate 3D models of bent tubes, allowing engineers to compare those scans to CAD master files to check for deviations.

Repeatable tube processing

“With the mechanical gages, you’d set the part in and you’d have certain clearances in certain areas,” Blasi says. The company needed more consistent results, he adds.

The Faro ScanArm, on the other hand, is fully repeatable. As tooling wears on the pipe bender, deviations in pipe shape show up more quickly, allowing employees to address problems before tubes fail during hydroforming.

“It shows us exactly where we are. One of our engineers is really good at that, and he can solve bent-tube issues in 10 or 15 minutes. That used to take us hours and we were never really sure we’d identified the problems,” Blasi notes.

“If I took the same part and put it in the gage five times, I could come up with five different outcomes.” - Mark Blasi, general manager American Hydroformers Inc.

The company considered coordinate measurement machines (CMMs) to create repeatable test processes for the tubes, but the Faro ScanArm offered more features – such as the portability to check CNC machining equipment at AHI’s sister companies and blue laser technology to scan reflective surfaces and complex geometries without targets or sprays. Tooling and process engineer Todd Champany says that while the Faro ScanArm is portable, it usually remains in the company’s metrology shop, checking tube dimensions.

“We have the option of bringing it to any part of our company to check anything. We can measure fixtures. We can measure machines,” Champany says. “We have taken it offsite to have our parts measured. We do that occasionally.”

Blasi adds that one part AHI forms needed 25 features laser-cut into its surface. So engineers brought the ScanArm to the laser-cutting shop to verify hole locations and add precision to the processes.

Hydroforming growth

Solving production bottlenecks was vital for AHI because of the growing popularity of hydroforming technology. Hydroforming is especially good at processing high-strength, low-alloy steel (HSLA), material favored for its ability to work-harden during a crash.

“If you’re in an automobile crash, as the car starts to deform, the steels harden and take energy away from the crash event. That’s energy that doesn’t reach the occupants,” Blasi explains. “Auto designers love this stuff in frame areas where it benefits crash performance, but they want complex shapes. That’s the challenge.”

Steel tube is processed with a CNC tube bender at American Hydroformers Inc. Out-of-spec tube bends caused problems for the shop, requiring inspection systems to identify problems early.

The main alternative to hydroforming structural components is to stamp an upper and a lower part then weld them together, a highly repeatable processes, Blasi says. With hydroforming, however, parts can be smaller and lighter yet stronger, because there are no welding materials or heat-affected zones surrounding the welds where material properties might change.

Developed for steel – Ford’s F-150 pickup has used hydroformed steel frame rails for more than a decade. General Motors developed hydroforming techniques to create steel frame rails for the Chevrolet Corvette more than a decade ago and adapted that process for aluminum with the 2013 Corvette Stingray. The 2016 Cadillac CT6 uses hydroformed aluminum components throughout its lightweight structure.

“It’s definitely a technology that supports lightweighting and multi-material construction, so we expect to see a lot more of it in the future,” Blasi says. “That’s why it’s so important for us to have the best processes in place for quality and productivity, and Faro enables that for us.”

American Hydroformers Inc. (AHI)

www.americanhydroformers.com

Faro Technologies Inc.

www.faro.com

IMTS 2016 Booth #E-5825

About the author: Robert Schoenberger is the editor of TMV and can be reached at 216.393.0271 or rschoenberger@gie.net.