Forum for Hydroforming

There has been a tremendous proliferation of hydroformed parts over the past decade, but particularly in the last six or seven years. Growth is still accelerating in North American and overseas markets. Probably 90 percent of the applications are automotive components.
Advantages of the process include weight savings, simplification of complex assemblies, superior crash worthiness, and the eliminating of superfluous parts and joints—all of which means lower costs and higher value vehicles. One of the largest shortcomings, however, is that the experience base with hydroforming is still quite limited and component applications must be conquered one at a time.

That is certainly happening anyway as more engine cradles, side rails, A-pillars, windshield headers, roll bars, exhaust components, axle supports and engine manifolds are added to the list, but the process could be speeded up and more predictably stabilized.

“Hydroforming is still a relatively young technology,” Tim Werding, president and CEO of Schuler Hydroforming, Inc., told us recently. “And it is still in transition from an art to a science.

Hydroforming is being used to make more automotive components, like this A-pillar frame for the BWM 3 Series convertible.

“We have been metal stamping for nearly 150 years so we have a tremendous knowledge base and also very dependable material specifications that accurately communicate the mechanical requirements. We need to get to that same level with specifications for hydroforming.” There is, of course, a fair amount of secrecy among hydroformers so the knowledge base is growing, but tends to advance in isolated pockets. Hydroformers don’t necessarily throw open their doors to competitors or potential competitors. That’s not about to happen anytime soon.

So Schuler constructed a state of the art hydroforming prototyping center in Canton, Mich., two years ago to ease and speed the process of applying hydroforming technology primarily to automotive applications. Schuler’s home base is Goppingen, Germany where it produces a full line of metal forming equipment and turn key production systems and is also well established in the hydroforming sphere.

The original mission of providing “hydroforming solutions” from the Canton facility evolved and now Schuler also provides actual production parts to a few OEMs. It is not particularly pushing that capability, but does provide that service when it can eliminate some crimp in the supply chain for a valued customer. As Werding explained, “Part of the reason we built the Canton facility was to have a place where people could see first hand how the process works, what equipment is involved and how the whole process fits together. The design process, the prototype process and the manufacturing process from start to finish.”

The Canton facility was conceived as a prototype center only, equipped to provide component development support, process design and optimization, aid with die design and manufacturing, prototyping, production line planning, installation and start-up, training and service. But it turns out some customers wanted even more. In some cases, they wanted Schuler to actually produce parts in pilot or in low volume production as either a Tier 2 or Tier 3 suppliers in situations where perhaps there was a capacity or timing problem.

“This was a delicate situation at the outset because to some extent we became somewhat of a competitor to our customers,” tells Werding. “But we convinced all of our customers that everyone was going to get something out of Schuler producing parts and dealing with the exact same practical day to day problems that they all have.

Schuler not only sells hydroforming equipment like the bending press (above) but manufactures parts for Tier 2 and Tier 3 suppliers as well as providing prototyping (below), component development support, process design and optimization, aid with die design and manufacturing, prototyping, production line planning, installation and start-up, training and service.

“Now that we are running our own presses, producing our own parts and meeting real schedules, I have to say that our viewpoint has changed. We have a much deeper appreciation for what our customers go through.”

The number one problem seems to boil down to the lack of a reliable hydroforming specific specification for incoming tubing.

Compared to conventional metal forming processes, the dramatic morphing of material in the hydroforming process causes the forces to act in directions that established specifications do not take into account.

“Some users look at tensile strength, or yield strength, or the spread between the two. Others say, no, look at the microstructure. Everyone has their own little recipe, but no one is really happy with the results because none of this is standardized,” explains Werding. “Everything is running fine and then you get a batch of tubing that meets a specification but yet the scrap rates soar. Hydroformers tell the mills they don’t know how to make tubing. Mills tell us maybe we don’t know how to form it. Of course the finger pointing really solves nothing. The problem may go away for awhile, but it will probably come back and you never know when.”

One year ago Schuler called on the hydroforming community to participate in a group called the HydroForum. Its mission is to be a “technology forum for interactive communication among hydroforming users in North America. The goal is to lead member companies toward superior competitiveness and profitability in their hydroforming divisions.”

The group currently meets twice each year and has developed a matrix of problem areas and topics for open discussion. Some 55 participants representing all major North American hydroformers are onboard. At its most recent meeting, tubing vendors were also asked to participate and did.

Though Schuler was instrumental in forming the group, it would be perfectly willing to relinquish its organizing role to some other hydroformer if that made sense. It is in somewhat of an unusual position since it makes the presses, but it does also make actual production parts. Whether Schuler continues in its organizational role or not, it will continue to participate in HydroForum.

According to Werding, developing a new test and specification for the inspection of incoming tubing has highest priority.

“In the end, my opinion is that we ultimately need an ASTM (American Society for Testing and Materials) specification for hydroforming tubes. I don’t know if we’ll get there, but I think one is needed. It would benefit the tube makers as well. Everyone wins.” What would the spec call for? “My inclination is that it will be some kind of burst test where you can establish the elongation at burst. We are actively exploring this. If we find a predictable correlation of that with scrap rate, then we are a step ahead,” says Werding. Europe is in no better shape for hydroforming material specifications than North America, perhaps worse. “In Europe things are even a lot more secretive than in the United States,” says Werding.. “Here we are at least getting people sitting together discussing it. They all say, yes, we have a problem. Let’s tackle it and we have made a beginning. In Europe, no, no, it’s all fine. No problem, basically. Well, that’s just not the case.”

If the correlation is between elongation and scrap rate does show correlation, what happens next? “If we have some good data,” says Werding, “then we have to convince the tube makers to take this tube burst test as some kind of a standard.

“If we all insist upon it, then we have some leverage and it will simplify everyone’s life including theirs. They will be seeing more hydroforming in the future, not less. But with a trustworthy specification, we can all proceed on a much smoother professional basis.”