|Starting point / Task definition|
|Borbet, a manufacturer of alloy wheels for cars and trucks, was looking for an automated solution for machining and painting that would be suitable not only with regard to variations in handling of the wheels during machine loading and unloading, but also for the interaction with the materials flow systems. Compared to the gantry robot which had been used up to that point, the new solution had to be more flexible, faster, and more cost-effective.|
|Implementation / Solution|
The company decided in favor of six-axis jointed-arm robots from KUKA, which are also notable for their short cycle times and high repeatability. First the wheel blanks are brought on a roller conveyor to the robot, where the type of wheel is detected by a camera. The KR 125 places the wheel on a turntable, where it is clamped and rotated, and then moves it to a cleaning station and a machining center. Here the robot uses its double gripper to carry out fine adjustment to ensure that the screw apertures can be drilled properly. The robot removes the finished wheel from the machine using the empty half of its gripper and loads the new wheel with a short swivel motion of its end-effector, thus eliminating wait times. The KR 125 wheel places the wheel, which is now ready for painting, on a roller conveyor. For truck wheels the cycle time is longer, and for this reason the robot only needs a single-element gripper. After pre-treatment, the center of mass and rotational position of the wheels are determined by cameras. The robot needs these data for tolerance compensation. An additional KR 125 uses a double gripper to position two car or truck wheels at a time flat on a floor conveyor, synchronized with the conveyor speed. In the following robotic cell, a KR 15 places balls in the apertures for the wheel screws, thus ensuring that they are not coated in the powder coating booth. In the next cell, a KR 125 transfers two wheels at a time to another conveyor leading through the baking furnace. It does this by inserting its three-jaw gripper into the central aperture of the wheels. This does not damage the powder coating. The transfer means that the spindles of the powder conveyor can simply be vacuumed clean afterwards. Before the KR 125 transfers the wheels to the second conveyor, it allows the central aperture to be cleaned completely of powder at a vacuum and brushing station. Before the next gripping operation the robot also cleans its gripper at a brushing station.
|Handling and machining of various wheels|
|System components / Scope of supply|
- Seven KUKA KR 125 robots and one KUKA KR 15 robot
- Eight PC-based KUKA robot controllers, including control panel with
- Single, double, and three-jaw grippers specially developed for this application
- Conveyor systems
- Image processing
- Robot programming
Supplied by KUKA system partner Boll GmbH, Elsenfeld in Lower Franconia, Germany.
|Results / Success|
- High cost-effectiveness
As linking elements, the robots make a decisive contribution to the cost-effectiveness of the wheel production. Without robots, many of the tasks could only be carried out with more expensive equipment, or with wage-intensive manual handling.
- Flexible adaptation
The flexibility of the robotic cells makes it possible to adapt them quickly to changing production conditions, even outside of their current broad spectrum of tasks.
- Faster than gantry robots
Thanks to their flexibility, six-axis jointed-arm robots are ultimately faster than gantry robots, which when carrying out the same tasks may even have to set the parts down periodically. Furthermore, jointed-arm robots achieve shorter cycle times when a number of operations are integrated in a single cell.
- High availability
In order to ensure high availability of the robots, KUKA system partner Boll installed a hotline and provided training to the user’s employees, one of whom attended two additional programming courses at KUKA College in Augsburg. In addition, support for the image processing systems of the robotic cells is provided via teleservicing. This enables Boll to help the user when, for example, a new wheel model is being introduced into the manufacturing process. Plans also exist to integrate the robots into the teleservicing in the future.
- An improved working environment
The working environment has been improved in areas where robots have replaced manual operations. This applies primarily to the handling of the heavy truck wheels, which had formerly led to health-related downtimes and thus additional costs.