Press Brakes

Land of the giants

By Lynn Stanley

Above: Ursviken’s Optima 2,750-ton, 40-ft.-long press brake reduces setup time for a major crane arm manufacturer with its integrated large offset punch adapter and quick-change slip-on nose radius punches.

The right technology features make the difference when bending heavy plate

July/August 2014 - When it comes to bending heavy plate, machine size matters—but knowing what to base a purchase decision on sometimes eludes manufacturers entering the rarefied world of these stately giants. 

“Most customers tend to be preoccupied with weight, length and price,” says Marten Weidgraaf, general manager for Ursviken Inc. “Little attention or thought is given to efficient tool setup and technology features that can improve setup and processing times.”

Press brakes, particularly larger models, share similar cycle times. Considerable time is spent loading and repositioning plate, checking bend angles and removing the work piece once a part is formed. “The critical elements are not how fast the high-speed approach or forming speed is, or how fast the press beam can cycle up, but how efficiently material can be manipulated in or out of the press brake so the operator can move to the next bend or work piece,” Weidgraaf explains. Understanding press brake features and how they differ from one brand to another can shed light on ways companies can make the most money from the machine they invest in. 

“It can be the difference between having equipment that ends up being a workhorse versus one that can serve as an effective, reliable racehorse for years to come,” he adds.


Problems solved

Studying the domain of the large press brake has helped Ursviken understand the equipment’s unique dynamics and has allowed the company to make inroads in the areas of automation, improved part accuracy and cycle times. This makes for operations that are both nimble and environmentally friendly. The 129-year-old company, with locations in Elgin, Illinois, and Ursviken, Sweden, designs and produces custom press brakes and specialty hydraulic presses for heavy plate forming. Sizes range from 100 to 12,000 tons. “We’re not a commodity press brake builder,” Weidgraaf explains. “We don’t run assembly lines. Instead, we have chosen to focus on engineering and innovation to help customers solve problems.”

Weidgraaf will tell you there aren’t a lot of companies manufacturing large press brakes 640 tons and up. “It’s a strange industry,” he adds. “Take the laser market for example. The technology is faster, saves energy and is advancing fairly quickly. Most fabricators that own a laser will buy a new one in as little as five years to keep pace with improvements. With press brakes the opposite is true. Once purchased, a press brake will most likely sit on a shop floor for 15 to 20 years. Tooling also is rarely changed out. Typically it is as old as or older than the press brake.”

To help guide customers in the market for a large press brake, Weidgraaf says he looks at key parameters like part drawings, tooling, material gauging and handling, and ram stroke requirements. “Everything that matters when it comes to providing an efficient process and application,” he adds. Correctly specifying a press brake also means looking at technology features that can contribute to enhancing efficiency.  “Large radius upper tools and changeover of upper and lower tools can take 30 to 40 minutes on a 1,000-ton, 24-ft. press brake,” Weidgraaf notes. “So it’s important to look at system designs that can improve efficiency in these areas.”


Faster, easier setup times

The first to design and produce a CNC variable die tool, Ursviken’s bottom variable die system and rotary upper tool rack can reduce setup time to less than five minutes. The operator simply selects the correct die opening from the CNC control system and the tool repositions itself to the new opening. For applications that require single vee dies, such as complex parts forming or short return flanges, Ursviken has integrated pneumatic lifting rails into its crowning table to allow dies to roll out of the machine into storage cassettes on a rail system located next to the press brake. Upper hydraulic tool clamping is built with integrated rollers along the length of the machine so that tools can be stored and loaded from the rack whether the operator needs one section or the total length of the tooling.

Customers also are looking for the best bend the first time, says Weidgraaf. To achieve that in a large press brake, correct tooling, gauging and angle measurement are key. “Plate that is 1 in. thick, 24 in. wide and 24 ft. long can cost up to severalURSVIKEN2 thousand dollars, so the bend has to be right,” he says. “The material’s higher tensile strength means a greater degree of springback. Without a means to check the bend angle in real time, part quality could be affected and processing will take longer, adding minutes to production time.” 

Part accuracy

A CNC-controlled crowning system is one way to maintain part accuracy over the full bending length, even outside side frames in larger press brakes. FlexiCrown is a mechanical wedge system divided into segments along its length so that a position system, with feedback, has the capability to arrange segments independently of each other. “We join the system’s wedges so they can be placed with a high degree of precision that is not influenced by negative forces like springback,” Weidgraaf explains. “FlexiCrown also has been designed to form an FEM calculated curve initiated by software that matches machine deflection in every bending process, yet gives the operator the flexibility to measure different areas and if necessary, modify crowning every 24 in.”  

A noncontact optical or laser angle measuring system can be integrated with FlexiCrown to automatically check angles along the table after the bend but prior to the beams returning to top dead center. “The operator is then able to move to the next bend or reposition the crowning station to repeat a bend cycle,” says Weidgraaf. “This technology also gives the operator forming quality and efficiency suited to long bends, bump bending and bending high tensile strength material.”



Bending parts to support manufacturing products like construction machinery, cranes, poles, pipe and tube requires a large press brake. But when the bending process is automated—a feat few suppliers have achieved—part quality and production efficiencies are enhanced.

One major manufacturer of mobile crane arms needed a fully automated press brake cell to produce a range of telescopic profiles. Plate material is fed from an automated material handling system and automatically loaded into different size press brakes 640 to 1,000 tons. Parts are run individually, not in batches. This arrangement allows the assembly line to receive required parts in order and eliminate the need for buffer storage. 

Offline programming initiates setup, plate positioning and bending. “During forming, all bends are checked for springback and compensated while the part is being held under pressure,” says Weidgraaf. “Most profiles specify different radii within the same part, requiring automatic repositioning of the variable lower die tool and punch radius indexing to the required size. Once the profile is completed, the part is automatically removed and the press brake readied for the next part. The company’s highly accurate bending results can only be obtained with an integrated mechanical angle measuring system or noncontact optical system due to one-off production and direct in-line feeding to an automated welding system.”

Each telescopic crane arm contains four sections with forming, moving from the smallest to the largest part. Although the crane arms are made in different sizes, material qualities and plate thicknesses, an FMS controller ensures the right products are correctly formed on demand, making the operation virtually automatic. “They need just one operator to monitor the machine,” says Weidgraaf. 

For jobs that require a larger vee opening, Ursviken developed a plate support and swing/sheet follower function that allows the press brake beam and swing to accurately synchronize each other while speed and position are maintained. 

Ursviken is also engineering new bending systems to handle forming challenges in the offshore and utility market. “Most of today’s pipe with a heavy wall thickness is processed on a plate roll,” says Weidgraaf. “A certain amount of prebending must be completed on both sides of the plate prior to roll forming to ensure the pipe is perfectly round.” For one manufacturer, prebending produced a flat that remained on the leading and trailing edges of the plate. Operators were required to machine or cut away these sections, creating additional labor and scrap. Ursviken’s new bending process virtually eliminated the flat reducing it one to two times depending on material thickness. 

“We’ve created a niche for ourselves in large press brake design and production as well as automation, but whether it’s a small press brake or a mammoth machine, the principles are the same—giving customers the features they need to be successful with higher throughput,” Weidgraaf says. FFJ



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