After hitting upon the idea of industrializing the building trade with the aid of prefabricated steel box panels, BSC began to search for an integrated automation solution for their production. The task was to prefabricate precision-fit elements in a large variety of shapes, sizes and widths. The difficulty until now was the question of how to bend the starting material: metal plates up to six meters long, five millimeters thick, and weighing up to 480 kilograms.

Implementation / Solution
 
BSC was finally able to implement the system with a team of two cooperating KUKA KR 500 robots, which carry out the handling tasks at the press brake. The decisive factor was the capability of the robots to work together as a team and the ability to integrate the robot controllers into the overall system program.

The plate, cut to size in a laser cutting unit, is carried by a roller conveyor to the two six-axis KR 500s. There it is pushed into a defined position by pneumatic cylinders. 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. Traversing along a common linear unit, the two KR 500s pick up the plate with their suction cup grippers. It takes two robots to handle the large plates. Otherwise, the plates would sag. Apart from that, they would be too heavy for a single robot.

The KR 500s rotate the plate, with complex counter-directional motions, in order to hold it in a defined position against the back gauges of the press brake.

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. Their motions correspond to the downward motion of the beam in the press brake. When the beam reaches its lowest position, the robots are also at the end point of their motion paths. After each bend, they set the plate down on a turntable which rotates it through 90 or 180 degrees. The setdown and pickup position on the turntable is programmed. Once the bending process has been completed, the robots set the steel box panel down on a support.

System components / Scope of supply

- Two KUKA KR 500 heavy-duty robots with a payload capacity of 500 kg each
- PC-based KUKA robot controllers, including control panel with familiar Windows interface
- RoboTeam technology
- Two suction cup grippers, each 2,600 millimeters long and 1,000 millimeters wide, and each fitted with six different suction cup modules that can be activated according to the specific task
- Linear unit
- Robot programming
- Start-up

Results / Success
 
High-precision synchronization

The use of cooperating robots is based on the RoboTeam technology from KUKA. The process ensures exact synchronization and geometrical coordination of all path motions and operations within the team. The high process accuracy results from the high-precision 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 workpiece.

Accurate to within a tenth of a millimeter

One precondition for the production of the box panels is an angular and dimensional accuracy of the bent parts of up to one tenth of a millimeter relative to the entire workpiece.

Short cycle time

As the robots achieve a cycle time of just 8.5 minutes, it is possible to process the planned annual quantity of approximately 400,000 square meters of metal plate.