Above: The Vario’s system makes it easy and fast to change V openings. Allowing a single operator to be productive on a large-size press brake.

Bending abrasion resistant steel delivers cost savings with the right tooling

May 2022 - Abrasion resistant (AR) steel plate is harder and tougher than high-strength structural plate and lasts four times longer. Tough yet formable, AR has primarily made its mark in mining and construction equipment. Growing demand to lightweight parts for mobile machinery-related applications has fabricators embracing the high-carbon alloy over more traditional choices such as other high-strength steels and aluminum.

“With fuel prices going up, if a truck is even 1 to 2 tons lighter, that helps a fleet operator save money and improve vehicle efficiency,” says Julio Alcacer, international sales manager for Rolleri USA.

“With ongoing logistics problems, this niche has grown aggressively in North America over the last two years.”

Headquartered in Vigolzone, Italy, Rolleri has designed and built precision press brake tooling since 1987. The company has 17 branches worldwide and has built its business on mastering the science behind bending challenging materials.

AR steels are created with alloys such as manganese, nickel, silicon or molybdenum and tempered to increase hardness. Such hardness makes the material attractive for lightweighting applications but can also create problems when it comes to bending parts. AR steels must be bent on a larger surface to avoid cracking. The process also dictates the use of upper tooling with a larger radius.

The Rolleri Vario is a patented adjustable press brake die system that eliminates setup time when changing V openings.

Know-how

“We can help fabricators eliminate press brake dead time and poor quality parts,” says Alcacer. “We learned to bend and form AR steel grades 10 years ago when Brazil experienced a boom in mineral commodities. A loading and hauling fleet that weighs less can carry a bigger payload. That means higher profitability. Bending AR steel isn’t just about strength. You don’t just buy a big machine. You need the right tooling and specialized knowledge about how the material will react under pressure.”

Ultimate tensile strength (UTS) refers to the maximum stress that AR steel can withstand while being stretched and pulled. “The higher the UTS, the more pressure you need to bend the part,” Alcacer explains. “A fabricator needs to know the chemical and mechanical properties of the steel and how to calculate blanks using press brake specifications. Tooling setup also has to be correct. Otherwise you run the risk of cracking the material.”

The Vario is easy to move, yet provides enough resistance to withstand 100 tons of pressure per foot.

To eliminate scrap and help manufacturers achieve precision parts from AR steels, Rolleri developed the adjustable Vario. A patented system of variable V slots, the tooling uses a V-shaped die opening to support the strength-to-weight ratio for each piece of steel to be formed. The Vario’s ribbed design allows the V die to be built with laminar steel versus solid plate. Lighter tooling is easier to move, yet provides enough resistance to withstand 100 tons per linear foot.

“An operator needs to make sure the die has enough resistance to withstand the force the brake will apply,” says Alcacer. “The die should allow the part to have a 15- to 20-degree springback. While there is no unique rule for bending AR steels, the die opening has to be at least 10 times the material’s thickness. The harder the steel, the larger the V die opening an operator needs.”

With the Vario, operators can bend abrasion resistant steels without cracking the material.

Strength multiplier

Punch radius and material thickness ratio are also not unique parameters. Typically the ratio should start at five times the material’s thickness but can go up as high as 12 to 14 times the material’s thickness. While a number of factors contribute to material springback, a tool with acute angles that will allow deep bends [those that can open to 90 degrees] is the best option. Unlike mild or stainless steel, bending AR steel with or against the grain is also critical. Not changing the punch radius to suit the material could cause damage to the part.

“Before an operator starts cutting, they need to make sure they know how they will bend the part and what direction the grain goes,” says Alcacer. “Once those factors are determined, the operator can choose the right tooling and program the press brake accordingly.”

Rolleri designed and developed the Vario based on intelligence it gained from its first concept—a massive shim channel die. “It had a couple of problems,” recalls Alcacer. “It could take up to four hours to change tooling on a 20-ft. to 24-ft.-long press brake. There was also considerable transportation and material costs. The Vario eliminates those issues.”

Alcacer sees demand for AR steel continuing to grow in the foreseeable future. “Rolleri has 30 years of bending experience,” Alcacer says. “We know what fabricators will encounter. Every day is a new challenge.” FFJ