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Sheet Metal

Making three into one

By Russ Olexa

February 2009- Just like every business, the German company Bedrunka+Hirth Gerätebau GmbH, Bräunlingen, Germany, must make its products faster, better and less expensively to compete in the European market.

To do this, it purchased a piece of equipment that’s not only permitted the company to process its parts faster, it’s allowed its components to be redesigned with fewer parts for easier production and elimination of downstream processes, lowering costs.

Bedrunka+Hirth’s product catalog shows 200 pages of various types of shop-storage equipment and work tables. The company makes a large variety of standard metal workshop tables, some having wood tops with drawers and others with movable stands for storing milling machine tools. The company also produces storage cabinets with sheet metal parts that accessorize all these products.

Many standard work tables can be modified with different drawer sizes, a back-frame sheet metal magnetic panel and other accessories to make a customized product.

Therefore, all additional parts must be readily available for production and assembly when an order is received. To do this, Bedrunka+Hirth adopted lean manufacturing processes and has no product inventory. Each is made on a just-in-time basis. Because it offers many variations on its primary product lines, the company must have manufacturing flexibility for its products.

Along with workshop furniture that represents 80 percent of its product turnover sold throughout Europe, Bedrunka+Hirth acts as a job shop, producing electronic and electrical cabinets for European and U.S. customers.

Production problems
Drawers for its products make up a major portion of the 1- and 2-mm-thick mild steel the company cuts and bends on a daily basis, with 80 employees working three shifts in a 5,000-sq.-m facility.

Originally, three parts were individually bent on press brakes and then welded together to form a drawer. This entailed a laser-cut or punched steel panel called a bottom wrapper (drawer bottom) that was then bent. Then, laser-cut or punched sheet steel front and back panels were added to this wrapper and welded together. This could take four to five minutes per drawer. Also, there were different drawer sizes in length, width and especially depth. Often, a tool cart would have four drawers. The top two drawers would be identical, but the two bottom drawers would be larger, with progressively greater depths. Therefore, it was imperative to build these products as efficiently as possible, and Bedrunka+Hirth knew using a press brake wasn’t the answer.

New folding technology
To begin the search for greater productivity, Jürgen Zimmermann, production manager, began looking at other methods of bending sheet metal. He discussed the production problems with companies that made automated folding units that used both up and down bending, with the metal sheet staying flat on the machine’s base.

One such company was RAS, Sindelfingen, Germany, which did a study for Bedrunka+Hirth showing how shorter cycle times could be obtained with RAS equipment.

When Bedrunka+Hirth received the RAS analysis, "We found that compared to our current production levels, the RAS Multibend Center could offer us greater productivity," says Zimmermann.

Then the company compared the RAS production study with what other suppliers of automated folders offered and found that RAS’ indicated cycle times were lower. Then RAS had to prove it.

"Bedrunka+Hirth looked at all of this information and found that the RAS Multibend Center could do more functions with its standard tooling compared to the other companies’ machines that had to use additional tools to bend similar features," says Willy Stahl, RAS president. "In fact, there were some parts that the other suppliers couldn’t bend on their folding equipment, even if they used special tooling. Taking the study into consideration, along with the capabilities of the RAS equipment, [Bedrunka+Hirth] finally decided to purchase our equipment."

Zimmermann says a 40-second cycle time was achieved using the RAS Multibend Center to fold a single panel that was cut and ready for bending into a drawer, compared with a five-minute cycle time for bending and welding the same drawer using three sheet metal parts.

"When Bedrunka+Hirth’s production problems were originally analyzed, our designers didn’t think of making the drawer from one piece of sheet metal that originally took three," says Zimmermann. "Our initial thought was to make our parts as productively as possible. However, seeing the features and capabilities of the RAS machine, we started to think about a redesign of our products by integrating multiple parts into one. We then realized the many other benefits of the RAS Multibend Center."

The lower cycle time for the drawer was achieved because the company could now automatically bend a complete drawer with the RAS Multibend Center folding machine. It no longer welded the pieces together. Instead, it used locking tabs that went through slots to secure the folded pieces of the drawer together. By using just one sheet metal panel for the drawer, it eliminated the need to design and plan for three panels to form a drawer, along with the labor and logistics to bring these panels together and place them into jigs for downstream welding. Production control needed to be concerned with only one panel for the drawer instead of three. The redesign eliminated the time for cutting or punching the two extra panels, along with the welding labor, mounting jigs and welding equipment.

New flexibility
In addition to a product redesign, Zimmermann says the RAS equipment offered greater flexibility for redesigning old and new products. "We’re now much closer to our market needs. The machine works on just one shift, but the result of its productivity is that we’ve replaced two press brakes manned by five contract people who are no longer needed."

He also says the machine has increased quality because of its precision bends, and "it’s much easier to keep up with the quality levels that have been established for our products."

"We could more easily form [Bedrunka+Hirth’s] parts, and they also counted on the service offered by us with our short distance from their factory," says Stahl. "They realized that what we promised during the sales process was fulfilled with our equipment."

Along with the RAS Multibend Center, Zimmermann wanted a way to have flexibility for different drawers and the capability to work unmanned. When Bedrunka+Hirth began looking into an automation bending system, it was also thinking about automating part loading. It asked RAS for advice on automatic material loading. A robot solution was offered because it was the most flexible tool available. RAS integrated a Kuka robot material handling system with its equipment, which can pick panels from four stations, allowing four drawers to be produced.

Although the company’s Amada CO2 laser and two Amada turret punches work three shifts, because of the RAS system’s speed, they’re only producing enough material for it to work just one shift. In fact, the company even added another Amada punch to increase production.

Bedrunka+Hirth is reorganizing its production needs, says Zimmermann. He feels that once the company has all of its products redesigned to use the flexibility and capabilities of the RAS Multibend Center, it’ll be able to increase its use.

Currently, the company has most of the drawer shapes redesigned and is still working on other parts. For downstream operations, Bedrunka+Hirth ordered a welding robot and other equipment to increase production. Then, Zimmermann wants to integrate a second material handling robot to move the bent drawers from the RAS system. The company will need the second robot to keep up with production and to introduce flexibility. Once installed, the RAS system will work two shifts.

Bedrunka+Hirth produces all of its products in-house. Its product processes include welding, spot welding, powder coating and final assembly.

The RAS Multibend Center has two models. The 79.22-2 has an 85-in. folding length, and the 79.26-2 has a 100-in. folding length. Both machines can handle up to 14-gauge mild steel, but with upgrades, they can handle 12-gauge mild steel.

The robotically controlled tool system is the heart of the bender. The upper beam tooling is segmented, which allows for any tool length and extra-deep boxes up to 8 in. tall. Open or closed hems and radii can be automatically produced in sequence without a tool change. Two complete sets of upper beam tools are available right and left of the center tool.

The servo-mechanic-driven upper beam clamps the blank to the lower beam. Then, the folding beam moves to the programmed angle and automatically folds radii, tabs, hems, offsets and closed profiles without any special tools.

The machine’s CNC control automatically calculates the fastest tool change strategy, even a tool change within a program cycle. Separate servo-motors for the left and right tool change grippers, along with reduced tool weights, allow rapid tool change times. A tool change is often completed before the next part is positioned to the bend line. For tapered parts, tool setup can be different on the left and right sides of the machine.

To quickly complete projects, multitasking is often required. For Bedrunka+Hirth and its combination equipment, it wouldn’t have it any other way. FFJ

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Sources

  • Bedrunka+Hirth Gerätebau GmbH
    Bräunlingen, Germany
    phone: +490/771-92-0135
    www.bedrunka-hirth.de

  • RAS Systems LLC
    Peachtree City, Ga.
    phone: 770/487-7300
    fax: 770/487-1007
    www.ras-systems.com
    e-mail: info@ras-systems.us

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