Bending of tubes
Starting point / Task definition

Since it is not possible to manufacture tube/hose/tube combinations in a single program cycle on conventional tube bending machines, Rosenberger AG was looking for a more flexible bending system which would at the same time provide outstanding precision, process reliability, and ease of operation.
Implementation / Solution
Bending of tubes
Bending of tubes

Created to meet these requirements is the TWISTER, a bending system incorporating a KUKA KR 16 robot – a patent application has been submitted for this system. Here, the robot functions as a fully-automatic CNC tube bending machine, which guides, depending on the specific task, from two to six bending heads designed for tubes with diameters from 20 to 60 millimeters. By executing the motions of a bending machine in the X, Y and Z axes, the robot uses up to three bending planes per head to create various bends, elongations and twists. The robot picks up the components using part-specific pneumatic finger grippers, which are developed for each individual application, and can be exchanged. The KR 16 fetches the tube itself, moves through the X, Y and Z coordinates under servo control, and thus with high precision, operates the bending heads and, if desired, also links the bending operation to other processes.

The first TWISTER was sold to an automotive components supplier. In this pilot project, the robot is used to form a tube/hose/tube combination with brazed-on fastening elements. The KR 16 grips the part at defined points. It then moves one of the outer ends of the tube to the right-hand bending head, which is used in this step to create six different bends. After each bend the robot turns the part as specified by its programming. It then turns its gripper around and holds the other end of the component against the right-hand bending head, which makes four more bends. As soon as this process is complete, the KR 16 swivels the part to the left-hand bending head, which bends the middle section of the tube by 180 degrees. In traditional production systems, additional manual intervention would be necessary here, since conventional machines can only make bends in a sequence corresponding to the direction of advance of the tube.

System components / Scope of supply

  • KUKA KR 16 robot
  • PC-based KUKA robot controller, including control panel with familiar Windows interface
  • Part-specific pneumatic finger grippers
  • Robot programming
  • Start-up
Results / Success

  • Guaranteed process reliability

    The positioning accuracy of the robot is to within a few hundredths of a millimeter. In addition to this very high repeatability, a primary advantage of the KR 16 is its flexibility, since unlike a tube bending machine it can let go of the components and then grip them again. This help guarantee process reliability, and is true for handling as well as for right-hand and left-hand bends. 

  • High cost-effectiveness

    Compared to conventional tube bending machines, with TWISTER the user can choose the number and position of the bending heads freely, and can use an extremely wide range of bending heads. This flexibility makes it possible to change over production quickly, even when manufacturing difficult parts, and automatic production is possible for even the smallest batch sizes – providing a lasting boost to productivity and cost-effectiveness. By installing multiple bending heads, the customer can also reduce his setting-up times. This is because when a sequence has been programmed and bending heads for various components have been fitted, all the user has to do is call up the appropriate program. When the program is switched, the KR 16 quickly exchanges its gripper if necessary. Although the capital investment for a TWISTER is slightly higher than for a standard bending machine, on the other hand the ability to dispense with manual operations provides large potential savings and thus a much shorter payback period. Moreover, it may be possible for TWISTER to perform tasks which would otherwise require a number of conventional machines.

  • Ease of operation

    To make operation easier, Rosenberger paid particular attention to development of the software. This benefits the set-up personnel, who can program the sequence via a programmable logic controller, visualized by means of a PC with Windows user interface, just as easily as if it were a “normal” tube bending machine.

  • Higher quality

    The uninterrupted nature of the robotic processes means that manual bending or finish-bending operations are also unnecessary. Previously, the parts had to be bent before they could be joined. In this case, each of the tube/hose/tube combinations had be picked up again by the operator and aligned. Since these potential sources of errors have now been eliminated, today Rosenberger achieves higher quality.
Number of report
R 249
Metal products
Other machining operations
Low payloads (5-16 kg)
KR C (Robot Controller)
Rosenberger Aktiengesellschaft, Gütenbach, Germany

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