BSC Bau-System-Center Entwicklungs- und Vertriebsgesellschaft mbH & Co. KG, based in Eisenhttenstadt, Germany, is the world’s only industrial manufacturer of customized building structures made from specially bent, large-area steel box panels. The company currently employs about 20 people. It supplies readymade, precision-fit elements in a wide variety of shapes and sizes, currently available in lengths of up to six meters (19.68 ft.).

The company was launched by Wolfgang Langer, who had the idea to industrialize the building trade with the aid of prefabricated steel box panels, and BSC searched for an integrated automation solution for its production.

Its challenge was to find a way to bend its starting material: metal plates up to six meters (19.68 ft.) long that weigh as much as 480 kg (1058.2 lbs.). BSC Bau-System- Center, was able to implement the system with a team of two robots provided by Kuka Robotics.

“Steel box panel technology can be used to industrialize the building trade. I had the idea back in 1989,” BSC Managing Director Wolfgang Langer said. “This system concept offers a great degree of planning flexibility and thus customer-specific solutions can be implemented.”

However, the technology requires careful, detailed preparation, before its advantages –time savings, improved quality and safety, and reduced environmental impact – can be realized.

Accurate to within a tenth of a millimeter
Langer had to wait 16 years, however, from the conception of his idea to a production system for the steel box panels. The reason is that it was simply not possible to bend such large, heavy panels either manually or automatically.

Kuka KR 500 robots were designated to carry out the material handling tasks at the start of the process, at the press brake. Two KR 500 robots work together to handle the material.

“The robots, with their payload capacity of 500 kg (1,102.3 lbs.) combined with their teamwork skills, provided the breakthrough,” Langer said. “Without cooperating robots, this production line would not exist. Another important factor was the ability to integrate the robot controllers into the overall system program.”

The use of cooperating robots is based on the RoboTeam technology from Augsburg-based Kuka Roboter GmbH. The process ensures exact synchronization and geometrical coordination of all path motions and operations within the team. The high process accuracy results from the highprecision synchronization and the real-time exchange of all the data required for the cooperation.

Each robot in the RoboTeam has its own standard controller. The KR 500 robots communicate with one another via a high-speed local Ethernet network and coordinate their actions. One robot is the team leader. Parallel to the RoboTeam, Kuka developed a new programming philosophy. Here, it is not the motion of the individual robots that is programmed, but that of the work piece.

Unique worldwide
The resulting production line is unique worldwide. It processes metal plates with maximum dimensions of 6,570 mm by 2,000 mm (21.55 ft. by 6.56 ft.) and a thickness of 5 millimeters (0.196 in.).

The production line is in operation around the clock, six days a week. Only 20 days a year are planned for maintenance and servicing. High availability is thus essential. The offline programming of the KR 500 robots also makes a major contribution, as the process is uncoupled from the manufacturing process, meaning that the robots can continue bending while programming is being carried out.

“One precondition for the production of the box panels is an angular and dimensional accuracy of up to one tenth of a millimeter relative to the entire work piece. Furthermore, we require a cycle time of 8.5 minutes in order to be able to process the planned annual quantity of approximately 400,000 m2 (4.3 million sq. ft.) of metal plate. The robots must also be very flexible, due to the varying lengths and widths of the finished steel box panels, which can measure from 2,800 mm to 6,000 mm (9.18 ft. to 19.68 ft.) and from 1,080 mm to 1,500 mm (3.54 ft. to 4.92 ft.) respectively.”

The flexibility of the KR 500s is also demonstrated by the fact that they can be operated independently of other machines in the system, so they can be exploited for such things as contract work.

Versatile grippers
Once a gantry crane has loaded a coil onto the coil lift truck of the line, the automatic process begins. This truck, which runs on a track, transfers the hot steel strip, weighing as much as 30 tons and 5 mm (0.196 in.) thick, to the uncoiler. The strip then is processed by a straightening unit, before a laser system cuts holes, corner indentations for the folds, apertures for supply lines and other order-specific apertures into the plate.

The plate is then carried by a roller conveyor to the two sixaxis KR 500s. It is first positioned against a stop and then pushed into a defined position by pneumatic cylinders. The process is monitored by sensors. If the dimensions of the plates change, BSC enters the new values into the computer.

The robots generally grip all plates centrally. In the case of very wide workpieces, however, the operators can also program an eccentric pickup position. Employees trained at Kuka College benefit here from the familiar Windows interface of the Kuka Control Panel.

Traversing along a common linear unit, the two KR 500s pick up the plate with their suction cup grippers which are 2,600 millimeters long and 1,000 millimeters wide. The end effectors developed for this application are each fitted with six different suction cup modules. Depending on the specific task, the system operator specifies via the controller which gripper modules are to be activated.

Complex, counterdirectional motions
It takes two robots to handle the plates, which can be up to six meters (19.68 ft.) long and weigh up to 480 kg (1,058.21 lbs.). Otherwise, the plates would sag. Additionally they would be too heavy for a single robot. Wolfgang Langer points to the KR 500s as they rotate a plate in order to hold it in a defined position against the back gauges of the press brake. “Just take a look at these complex, counter-directional motions. They clearly show that cooperating robots were the only possible solution for this application.”

The plates are bent on all four sides, with each side being bent twice at an angle of 90 degrees. They are guided by the KR 500s during these process steps. Their motions correspond to the downward motion of the beam in the press brake. In other words, when the beam reaches its lowest position, the robots are also at the end point of their motion paths.

The KR 500s bend first the long sides and then the short sides of the plate. After each bend, they set the plate down on a turntable which rotates it through 90 or 180 degrees.

The sit-down and pickup position on the turntable is programmed. Once the bending process has been completed, the Kuka robots set the steel box panel down on a support. From here, the workpieces are carried away on a roller conveyor to be welded.

With the new automated system in place the company has increased production, improved safety & quality and decreased costs.

For additional information, contact Kuka Robotics Corp.,(www.kukarobotics.com) or 866-873-5852.