Handling of front and rear axles and car doors

This case history about BMW comes courtesy of KUKA Robotics Corp. It has been selected and edited by the MHM editorial staff for clarity, content and style.

Starting point / Task definition
For its Regensburg plant, BMW was looking to implement automation solutions for the handling of complete front and rear axles for the 1 Series and 3 Series, as well as for the handling of doors for these series.

Implementation / Solution
For the handling of the front and rear axles, BMW chose three KUKA robots: one KR 500 and two KR 360s. The KR 500 takes the assembled front axles from the assembly system and sets them down on assembly aggregate carriers (known as MATs). The KR 500’s combination gripper is suitable for each model-specific axle of the 1 Series and 3 Series. Furthermore, this complex gripper fulfils BMW’s requirement that the parts of the axle which can still move during the handling process are held in place in the specified position. This enables the robot to precisely position all of the screw-on components on the MAT.

The two KR 360 heavy-duty robots handle the rear axles. The first KR 360 picks up the axles from the assembly system and places them in a magazine on combination workpiece carriers. The second KR 360 unloads the magazine and sets the axles down on the MAT. As with the front axle, the precise set-down position required for this operation is determined by a Perceptron measuring system. In order to place the KR 360s in the optimal position for their assigned tasks, they are mounted on bases which are one and a half meters high. Thanks to their special grippers, they can handle all of the vehicle axles processed at the Regensburg plant. Because the robot controllers move the grippers as the seventh robot axis, the KR 360s are additionally able to hold the car axles by their wheel hubs regardless of the wheel spacing.

For the handling of the car doors, four KR 150 robots, working in pairs and equipped with 400 mm arm extensions, have replaced the same number of lift stations and their associated transfer machinery. In each robot pair, one KR 150 is assigned to the front doors, and one to the rear doors. The robots’ sequence begins when an electric overhead conveyor vehicle stops in the station with an empty hanger. The KR 150 concerned moves its gripper with a swivel motion into the load-bearing unit, lifts it out of the electric overhead conveyor vehicle, and moves it down a level, ready for loading. Two operators stationed there load doors for the corresponding vehicle body onto both sides of the hanger. After this, the robot moves the load-bearing unit back to the upper level, and returns it to the electric overhead conveyor. The high repeatability of the robots makes it possible to avoid damage to the doors and the electric overhead conveyor. And, because the robots can be programmed freely, the system has a high level of flexibility. Moreover, KUKA was able to satisfy BMW’s desire for reliable grippers of simple design.

System components / Scope of supply
- One KUKA KR 500 heavy-duty robot with a payload of 500 kg
- Two KUKA KR 360 heavy-duty robots with a payload of 360 kg each
- Four KUKA KR 150 robots with a payload of 150 kg each
- PC-based KUKA robot controllers, including control panel with familiar Windows interface
- Grippers
- Robot programming
- Commissioning

Results / Success

High flexibility
The three heavy-duty robots provide an axis handling solution with a very high degree of flexibility with regard to changing product requirements. BMW is equally flexible in terms of the KUKA robots’ installation sites, which can largely be freely chosen, thanks to the robots’ large working area.

Increased availability
Removing the lift stations, which no longer corresponded to the state of the art, and replacing them with KUKA robots resulted in an increase in availability. Furthermore, it was also possible to use these high-performance, standardized robots to optimize the process.

Integrated emergency strategy
BMW also benefits from an integrated emergency strategy. If a fault should occur in a KR 150, the second pair of robots takes over the tasks of the first pair in addition to its own. In this event, the user temporarily increases the output of the operational pair of robots to 100%, thus adapting them to the cycle of the electric overhead conveyor.

Short commissioning time
Another advantage of the robots is their short commissioning time. This is due, for example, to standardized interfaces between the higher-level controllers and the robot controllers, as well as the use of service-proven software modules.

MHMonline.com welcomes relevant, exclusive case histories that explain in specific detail the business benefits that new software and material-handling equipment has provided to specific users. Send submissions to Clyde Witt([email protected]), MHM Editor-in-Cheif. All submissions will be edited for clarity, content and style.

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