Showing the potential that the tubular hydroforming process provides, Schuler North America is expanding its Hydroforming Production Center by 10,000 sq. ft. to make room for a new 5,000-ton hydroforming press, bending cell and automation technology. Construction is well underway and the new technology should be up and running in 2025.
Schuler North America, headquartered in Canton, Mich., provides press systems, spare parts and a portfolio of lifecycle services. The production center is unique, however, in that it provides full-service tubular hydroforming production. The center also develops new dies for customers, helps them integrate the dies into their tubular hydroforming operations and provides part design input to make it possible for parts to be tubular hydroformed.
Currently, the production center hosts 3,500-ton and 8,500-ton tubular hydroforming presses with the latter being the largest hydroforming press in the United States. The new press, currently being manufactured in Brazil by Schuler Group subsidiary Prensas Schuler, will provide greater flexibility in moving jobs between all three presses.
Auto assist
The production center’s customer base is primarily in the automotive industry. Tubular hydroforming is a successful technology for lightweighting vehicles.
“Typically, the automotive customer wants to take weight out for cost savings,” says Chris McMahon, sales manager, hydroforming, Schuler North America. “This is very simple to do with tubular hydroforming.”
He notes that tubular hydroforming in the past was used to produce a variety of other parts – from refrigerator handles to bike frames. However, the roll-forming process has evolved and is now used for many of those profiles. But, for automotive and off highway vehicles, tubular hydroforming – and the full-service tubular hydroforming production center – is a perfect fit.
“We do tool [die] builds for automotive OEMs – whether it’s for a Schuler press or not – where we provide the tool and provide input on the part design to determine what would make the part a candidate for tubular hydroforming,” McMahon adds. “We do the build and the buy-off and then help them integrate that into their operations.”
Finding an answer
McMahon provides the example of a customer that had an assembly for an off-highway vehicle that had nine unique components that required some stampings and straight tubes that were welded together.
“We worked with them over a couple years,” he says, “and were able to incorporate their assembled part into one hydroformed tube, which ultimately gave them a less costly part. It was a more consistent part, too, because all that stamping and welding puts a lot of heat into the process and that heat caused inconsistencies from part to part. The customer arrived at a stronger finished assembly using the tubular hydroformed part.
“We have a great team of experts that know the press inside out,” McMahon adds. “It’s not just the equipment but the knowledge. They know how to do the FEA analysis, which is the simulation, to help customers understand how a part can be tubular hydroformed. They can help determine before any metal is cut if the part makes sense. Not just ‘is it possible to be hydroformed,’ but ‘does it make sense.’ We can also do the prototyping and obviously the tool build.”
The production facility also does some secondary operations, such as laser cutting and finishing.
“When tubular hydroforming the part, we have to seal the ends, so we may have to roll them and so we like to laser cut those ends off to get the finished part,” McMahon says. “We can pierce holes and features into the die, but there’s a limitation on how many holes we can pierce so we also do some laser cutting. Sometimes, customers want the holes laser cut anyway because it is easier for them to make an engineering change. Adding or deleting a hole is a lot easier to do in a laser program than it is in a die. We also added bending capability for tubes to be able to use them in the hydroforming process.”
The process details
The tubular hydroforming process involves loading a tube into a die and using water pressure to shape the tube. Most of the water used to form the parts can be recycled, too.
“Basically, we take a straight tube, load it into a die, use the hydraulic press to close the die, hold the tonnage and then use axial cylinders to seal the ends of the tubes to apply the pressure for hydroforming,” McMahon says. “We use a hydraulic intensifier so it builds pressure anywhere from 1,000 to 4,000 bar, so 10,000 to 39,000 psi, to form the shape. The die is closer to a mold than a stamping die, but it is a die.”
Typical tubes that are hydroformed have a 2-mm to 3-mm wall thickness, depending on the customer application or the end use for the part. McMahon notes that the team has worked on parts with wall thicknesses of 16 mm, although that is an extreme example.
Typical materials used include mild steel, stainless steel and aluminum. “We are also very competent in high-strength steel and dual-phase steels, which are important for lightweighting and maintaining strength,” he adds.
Gives the advantage
The advantages of tubular hydroforming include eliminating secondary operations and providing consistent results. “Because the die is more of a mold than a stamping die, the process is very repeatable, very consistent,” McMahon says. “A good comparison would be specific to structural part production. With stamping, you can stamp two profiles and weld them together. With hydroforming, you can take a tube and form it and more or less get the same end result. It often requires fewer operations and is more repeatable, which is less costly than stamping and welding a part.”
Another advantage of tubular hydroforming is that it also workhardens the steel.
“We have some parts where we start with a particular grade of steel and then after the tubular hydroforming process, it is stronger than when it started,” McMahon says. “We start with a lesser KSI steel and bring it up to a higher KSI level and the finished part is ultimately a stronger tube.”
As an example, a customer needed to produce some frame components that had a very specific tolerance.
“Through the workhardening and the strengthening, we were able to change the shape,” McMahon says. “We took a round tube and put a square section in the middle so that gave the customer a stronger part as well as an area where they could weld parts to it.”
Still another advantage of tubular hydroforming is forming parts that have different wall thicknesses using the same die.
“We currently make a 4-mm-thick part and a 6-mm-thick part in the same die,” McMahon says. “We just change the seal cone in a matter of minutes. We’re able to make two different parts with different wall thicknesses using the same die. That is not possible with stamping where you’d have to change everything and shim everything up. We’re able to do that with tubular hydroforming with little adjustment.”
As for challenges with tubular hydroforming, the biggest one is determining if the end product lends itself to tubular design. It must have the right profile for it to be a fit. The part may not meet the criteria or the tool investment might be too high. But overall, tubular hydroforming offers many advantages and produces high-quality parts for use in automotive and other industries.
Hydroforming Production Center
