Kuka robot in multi-stage washing application
It is no longer possible to imagine automotive production without robots. At the BMW Group plant in Dingolfing, a Kuka robot operates in an environment in which other industrial robots are simply unable to work. The robot, of type KR 120 R2100 nano F exclusive, is installed in a washing cell where it is exposed to cleaning fluids with chemical additives, high temperatures and high cleaning pressures.
Industrial robots are characterized particularly by precision, short cycle times and high flexibility. The KR Quantec nano F exclusive, the washing expert from Augsburg-based automation specialist Kuka, offers an additional advantage: it is specially designed for the extreme conditions in cleaning systems. Cleaning fluids, high air humidity and chemical additives are no problem for it. “This robot was selected due to its robustness and flexibility,” says Robert Heimerl, responsible for sales and project management in the field of automation at Schnupp GmbH & Co. Hydraulik KG, stating the primary reasons for integration of this robot in a washing cell. The robot guides the components, which are destined for installation in the roof assembly of the body for various vehicle models, to the nozzle holders where they are cleaned to remove forming agents and dirt particles that may be present from the production process. Schnupp GmbH, with headquarters in the Lower Bavarian town of Bogen, specializes in systems and mechanical engineering and equips its customers from the manufacturing industries and automotive manufacturers with complete solutions, for example in the fields of automation and hydraulics.
Cleaning in five work steps
Heimerl and his team were familiar with the automated linking of a production process. The process in question involves the forming and finishing of steel components of various sizes. WK Systemtechnik GmbH & Co. KG was tasked with the design and implementation of the washing cell which, according to Heimerl, is centered on a new washing system. “The challenging part of the implementation was integrating the robotic washing cell into the robot linking. Due to the spatial constraints, it was not possible to install a continuous-flow cleaning system,” says Herbert Winter, CEO of WK Systemtechnik, whose company based in the Lower Bavarian town of Spiegelau specializes in industrial robotic cleaning systems for automated in-line cleaning processes.
In a first step, the KR Quantec nano F exclusive uses a special multiple gripper to pick up the component from the infeed unit. In a second step, the hollow cavity of the component is cleaned. For this, the robot feeds the component to the internal cleaning operation with millimeter precision. Following the first cleaning stage, the component is moved onward to the cleaning nozzles. Here, external cleaning is carried out. This is followed by neutralization of the interior of the component by rinsing with deionized water. In the final step, the robot, having held the component stably in the specified position throughout the washing process, sets it down on the outfeed transfer unit. There, before being removed from the washing cell, it is also rinsed on the outside.
The challenge for the Kuka robot
The environment in which the Kuka robot performs its task is not normally suitable for industrial robots, as the robot is exposed to large quantities of water with 3% alkaline cleaning agents added. Furthermore, temperatures in the washing cell can exceed 60° Celsius, resulting in considerable water vapor. Special protective measures have been taken to ensure that the Kuka robot is not damaged by these external influences. It features complete encapsulation of the mechanical system and pressurization of the robot interior. The cable set is routed internally throughout the robot. Moreover, the protective surface is resistant to alkalis, acids, heat and corrosion. That is why, unlike most other Kuka robots, this robot is not painted orange. Together with its fixtures, it meets the requirements of protection rating IP69.
A further argument in favor of the Kuka robot is its high degree of flexibility and fast cycle times. The entire washing operation can be performed in 45 seconds and components of different sizes can be processed. “The required cycle times and the different geometries of the components were only possible with this special robot variant. Due to the confined installation space, the freedom of motion of a conventional robot with a protective suit would not have been sufficient,” explains Winter.
Heimerl too is satisfied with the system, not least because it even met the customer’s requirement for component handling under a water spray. Since commissioning in the summer of 2015, the system has proved its worth. Follow-up inquiries have meanwhile been received for the automation of further cleaning processes with a robotic cleaning system.