Press brake proxies
- Created: 2017-05-05
Two similar yet different bending technologies give press brakes a run for their money
by Kip Hanson, senior editor
Panel benders and folding systems are great machines for processing large parts that would be awkward to handle on a press brake. There’s no need for multiple workers to wrangle heavy sheets into position; no need for sheet lifters or expensive automation. On a panel bender or folding machine, one operator can manage even the largest of sheets with ease.
But these machines are also more limited than press brakes in terms of material thickness and flange height, and both are – at first glance – more expensive than their die bending counterparts. To those who’ve built a business on press brakes and have a team of operators trained in their use, why bother with what many consider a niche, relatively unknown machine tool technology?
David Prokop, vice president at MetalForming Inc., has one good reason: Give a panel bender or folder the right part and either machine will blow the throughput doors off a press brake.
“That’s not to say press brakes don't have their place in the average shop, because they do,” he says. “Small parts that are easy to manipulate are good candidates for a press brake, as are super long parts used in windmill structures or tall storage racks, for example, or parts with weld nuts and inserts close to the bend line. But anytime you reach a size where the operator struggles with part handling, it’s a good indication you need to look at a different bending technology.”
What’s in a name?
Let’s start with some terminology. According to Bill Bossard, president of Salvagnini America Inc., the panel bender was invented in 1976 by the company’s founder, Italian engineer Dr. Guido Salvagnini.
The machine uses a blade that makes contact with the workpiece and then interpolates an arc equal to the desired bend radius. Salvagnini’s method is more accurate and less marring to materials than the wiping motion used on some panel benders and when performing horizontal bending on a press brake.
Folding machine, on the other hand, use a folding beam to fold the workpiece around a tool mounted on the machine’s clamping beam, a technology that should be familiar to anyone who has operated a manual bending brake, or who practices origami. Compared to panel bending and even press brakes, folding is the veteran on the sheet metal block.
Machine builder Schechtl, for example, represented in North America by MetalForming, has been building folding equipment for the architectural industry for more than 100 years, although Prokop is quick to point out that the company’s current versions use computerized graphical controls. To service the industrial market, MetalForming represents the Schröder folder, which offers automatic tool change systems and is capable of extreme automation.
As mentioned, both technologies share some common ground:
- The sheet is held flat in either case, similar to a shear or turret punch, so there’s no need to grab half a dozen helpers when bending a section of aircraft wing or a garage door panel.
- The tooling for panel benders and folders is far more universal than tooling used on press brakes; the user is able to do more shapes with fewer tools. This also makes it more expensive, although the total investment is arguably less than tooling up a press brake.
- When bending mild steel, panel benders and folders are more limited compared to press brakes in terms of material thickness and flange height. Panel benders are limited to sheet thickness of around 0.12 in. (3 mm) and flange heights of 10 in. or so. Folders can handle roughly twice that, in thickness and flange height alike.
- As a rule, automation is simpler and therefore more common on folders and panel benders, although that balance is beginning to shift as robots and automatic tool changers become increasingly prevalent on press brakes.
- Automated or not, both machines are considered “single piece flow” technologies, and, properly tooled, are less batch-oriented than most press brakes.
MetalForming offers both panel bending equipment and folding systems, but most of its customers lean toward the latter.
“The perfect part for a panel bender is made of light-gauge material, shallow and symmetrical around its center, and it’s often high volume,” Prokop says. “Think panels, doors, pans, trays or shelving. Folding machines, however, can handle thicker materials and taller flange heights, making them more suitable for job shops and general purpose manufacturing where a variety of work must be done.”
Salvagnini panel benders use an interpolated motion to accurately bend steel sheets up to 3 mm thick, and aluminum up to 4 mm.
Agree to agree
Despite their differences, Prokop and Salvagnini’s Bossard agree that press brakes are a necessary part of the production floor. But both suggest fab shop owners and management are doing themselves a disservice by not looking at panel benders and folders.
“A press brake by definition is a universal tool,” Bossard says. “There's nothing that needs to be formed that can’t be formed on a press brake. But let's not confuse the degree of accuracy, repeatability and ease of setup that comes with panel benders and folding systems because press brakes simply don’t measure up in these areas.”
Bill Kennedy is another member of the folding machine fan club. The vice president of RAS Systems LLC says the reason why so many press brakes are in service is simple: Most shops don't know there are alternative solutions available with the potential to dramatically increase throughput. “When there’s a bottleneck in the bending department, they say, ‘Hey, let's buy another brake.’ They don’t stop to investigate the alternatives.”
Kennedy notes that in Europe, the situation is reversed. Because the technology has been around much longer overseas, a shop might start out with a few folders and then add a press brake for thicker materials or relatively small blank applications.
In the United States, it’s just the opposite – unless the shop specializes in architectural work, they typically buy the press brake first and maybe get a folder or panel bender if a specific application warrants it. In either case, it’s important to recognize that all of these machine tools are complementary to one other and shouldn’t be considered as competitive.
Like his colleagues at MetalForming, Kennedy offers both types of machines, but he’s fairly relaxed over the terminology.
“When panel benders first emerged, they were machines designed for a particular type of work: fairly consistent dimensioned panels,” he explains. “Today they’re computer controlled, often but not always automated to the fullest capability, and offer a lot more flexibility than their predecessors. Some use a wiping action while others clamp and fold, but to me they’re all CNC folding machines.”
“The other advantage panel benders have over press brakes is their ability to form complex geometries more easily,” says Tom Bailey, TruBend product manager at Trumpf Inc. “Things like large radius bending, offset bends, hemming, folding and flattening – these special bending operations require specialized tooling on a press brake. And as soon as you start talking about specialized tooling, you're talking about longer setup times and potentially multiple setups. With a panel bender you generally have fewer tool changes and can achieve a much wider variety of bending operations in a single setup using the standard toolset that comes with the machine.”
Another advantage is simplified automation, which according to Bailey is “old hat” on a folder or panel bender. There’s no need for a robot capable of replicating the touchy-feely, very human motion required to support the workpiece as it moves through its bend arc like there is on an automated press brake.
One might think easier automation would equate to a lower price tag, but sadly for would-be panel bender owners, this isn’t the case. Bailey says take the starting price for a high quality press brake and roughly double it by adding automation, then tack on another 50 percent or so for an automated panel bender or folding system.
That might seem like a big difference, but considering that a “pretty fast” hydraulic press brake takes around six to eight seconds for every bend compared to a panel bender’s ability to produce one bend per second (depending on the distance is has to travel), it is five or six times faster than a press brake, at least on a per bend basis.
And what about the learning curve? Everyone interviewed for this article agrees that press brakes are more difficult to set up and operate, making panel benders and folders attractive to anyone struggling to find experienced operators.
Yet Bailey offers one final bit of advice to those in the market for a new machine. “You definitely have to rethink bending. If you're used to press brakes and decide to venture into panel bending or folding territory, it's a great way to expand your capabilities as an OEM or contract manufacturer, but you can't look at it as being a fancy, automated press brake. It's definitely different in terms of how you achieve your required throughput, how you tool the machine and how you program it. You need to look at it as a completely new process.”