KUKA robots work alongside RAS Multibend-Center in state-of-the-art production line

Multibend-Center is the name of the bending centre from RAS Reinhardt Maschinenbau GmbH for flexible sheet-metal working. In a state-of-the-art production line, two KUKA robots load and unload this unique bending system. The robots, with their "integrated intelligence", communicate with the cell control computer and the CNC program of the machine, thus enabling full automation of operations, from the high-bay warehouse and the bending process to the unloading of finished parts onto a pallet.

RAS Reinhardt Maschinenbau GmbH was founded in 1939. It is a medium-sized family-owned company with a workforce of 210 and sales of 25 million euro in 2005. The core competencies are in the fields of cutting, bending and forming. In addition to the headquarters in Sindelfingen and a component production plant in Wildberg-Effringen, RAS operates a sales and servicing subsidiary in USA and works with agents in 30 countries around the world.

With the new high-tech robotic system, RAS is responding early to meet market demands for greater automation in bending processes.

In the RAS bending center, the metal sheet is bent using a scratch-free process in which the sheet remains lying on the work surface and is moved by manipulators in the machine. It is loaded with blanks by one KUKA robot, and a second KUKA robot unloads the finished bent parts. Neither are taught, working instead with their "integrated intelligence". "For the user, this means: simple operator control and time savings, as programming is dispensed with," explains RAS Managing Director Willy Stahl. The system is networked directly with the customer's high-bay warehouse. The pallet for the finished parts has a matrix code, which requests the stamped sheets from the warehouse.

The first KUKA robot, a KR 150-2, picks up the blanks from one of the stacks of sheets on the shelf pallet, turns them over and feeds them to the RAS Multibend-Center.

Following the bending process, the second robot unloads the boxes and panels and stacks them on the waiting finished parts pallet. The robots communicate with the CNC machine and the central computer via the RAS cell control computer. Sounds like high-tech? It is.

Ordering of materials via barcode

The sheets to be processed come directly from the high-bay warehouse. The order of sheets for the empty pallet is compiled there by the warehouse management system. The pallet, meanwhile, has been placed on a conveyor belt by a forklift truck and moves past a scanner. The scanner reads the 3D matrix code on the pallet. In this way, the system knows what product belongs on this pallet. The information is fed into the cell computer. It includes the article number, quantity and current pallet size.

The cell computer forwards these data to the high-bay warehouse, which is controlled by a warehouse management program. The sheet metal blanks are taken from this storage facility. As soon as the pallet is dispatched from the warehouse, the cell computer receives information about the height of the stack of material to be processed.

The first KUKA robot is now responsible for loading the machine with the metal sheet to be bent.

The KUKA robot "knows" how many sheets it has in its gripper

The KUKA robot takes the sheet to be processed from one of the stacks. It can access up to four different stacks in different positions and even of different heights. The robot reaches out for the blank and peels it off the stack using a suction device to separate it from the remaining blanks.

It then weighs the blank, to confirm once again that it has only picked up one blank. Before the sheet enters the Multibend-Center, the robot rotates it to ensure that the sharp stamped edges end up on the inside of the bent part and the paint finish on the correct side.

For this purpose, the KUKA robot rotates its entire wrist so the blank now lies on top of it as if on a table. In order to prevent damage to the suction cups on the gripper, the suction cups are retracted while grippers pull the blank into the bending center.

By the time the processed sheet has made its way through the Multi-bend-Center, the pallet for the finished parts has reached the position by the unloading robot.

"The scanner was deliberately placed upstream," explains Wolfgang Kutschker, Head of Development at RAS. "This gives us an advance buffer for individual orders. In other words, while the second KUKA robot is loading one pallet, the cell control computer is already forwarding information for subsequent orders to the warehouse management system."

Two possible routes for the finished bent part

When the bent parts leave the Multibend-Center, they can go one of two ways. The first possibility is that they land on a buffer table that has been integrated into the system for urgent orders. This is the exception, however. Generally, the CNC program instructs the robot to stack the parts on the pallet that has just sent its order via the computer to the high-bay warehouse and is now waiting to be loaded accordingly.

The second KUKA robot is informed by the bending program how it should best stack the parts in the box, since they fit differently according to their shape and size. For certain stacking patterns, it even has to turn them over. For this reason, the system also has a turnover station. The robot places the bent sheet in this station and changes its grip before picking it back up again.

Once it has loaded a pallet, the KUKA robot receives the next order and starts stacking again.

"We are very proud of having achieved this system concept in such a short time," says Managing Director Willy Stahl. In total, the project only took about four months to implement. "Our customer can integrate it smoothly into his production operations." The system requires very little maintenance.

"This was also a reason for turning to KUKA robots. They are renowned for their reliability," adds the Managing Director. "Furthermore, it is very important, during the implementation phase, to be working together with partners located near by. In this way, it is possible to sit down together at any phase of the project and consider and discuss solutions to problems. This has already worked very well with KUKA in the past." And not just nationally. RAS USA has also already installed a KR 140 comp in a Multibend-Center - the result of international cooperation between KUKA Roboter and RAS Sindelfingen.