TechTuesday: Fortsetzung

Posted By on 2015-02-10


Want to know more about the Gestamp plant in Bielefeld? How did the team solve all of those challenges described last week?

KUKA’s project management responsibilities included careful planning of design, production and installation as well as highly detailed and close coordination of schedules and deadlines with all partners. Project management also involved mandatory testing of components and fixtures for all subassemblies and add-on parts in master cells at KUKA in Augsburg.

Acceptance tests and process evaluations were conducted together with Gestamp. These tests ensured that all components met high quality standards prior to delivery. At about the same time, the installation of standard cells (as yet without fixtures) began at the Bielefeld plant. The interconnections and the main line, which includes geometry-determining stations (GEO line), were also set up during this time. KUKA used several of its own proven standard solutions and products in the field of robotic, automation and welding technology. This was a clear advantage allowing for much faster implementation of the newly designed system.

The various subassemblies are then joined and processed with the correct dimensions on a highly automated GEO line with nine processing stations. Several compact buffers are integrated between subassembly production and the GEO line as well as within the GEO line itself. Among other things, these buffers ensure that the loading. process is sufficiently independent of the system cycle in accordance with material flow simulations, which are used as a basis for calculating the optimal output in advance. KUKA performed studies and simulations for other aspects such as the layout, component clamping concepts, welding process, workflow time analyses (MTM, methodstime management), ergonomics, accessibility and cycle times. KUKA had thus completed all tasks and found reliable solutions.

The specialists at Gestamp are experts at manufacturing high-quality chassis components and have many years of process expertise. Together with KUKA, they discussed and evaluated all tasks and solutions that affected components and processing. They then agreed on goals that would provide the framework for the detailed designs that would follow.

During this reengineering phase, all peripheral criteria, process requirements and production steps were virtually tested, validated and optimized. For example, this involved studying the motion sequences of the individual robots in order to prevent collisions and to ensure that the planned reach and accessibility satisfied the challenging process requirements. Using these RobCad simulations, the robot-assisted arc welding tasks were programmed offline prior to commissioning. These tasks could then be much more easily integrated into the KUKA KR C4 robot controller and adjusted to actual requirements on site, significantly reducing the start-up time.

Linearportale

To compensate for space restrictions in material transfer, three linear gantries measuring up to 75 meters in length are installed high above the production cells. Twelve carriages, several of which are equipped with rotary units, move along these gantries. In addition, a complex logic had to be followed. For example, the 13 different assemblies for side members and cross members had to be transferred at the right time by only four carriages to compact storage stations. In addition, the entire ladder frame was rotated by 180 degrees in several GEO stations to provide further buffer capacity in these stations. This presented another highly complex challenge with respect to space restrictions and workflows. If faults occur in downstream areas and a frame is ready for the next station, it is rotated sideways. This frees up space in the station so that another frame can be moved in and processed.

With KUKA’s assembly solution, two gantries move the side and cross members to a temporary buffer station that supplies the GEO line with the subassemblies. All side member subassemblies, including reinforcement parts, are then built in one station on the GEO line. In a further loading station, the welded side members and the seven cross members are loaded with a multi-gripper and pre-positioned. These actions ensure that the positions of all frame subassemblies in the first GEO station can be very precisely coordinated for welding. The success of this project was a testament to this KUKA joining concept: only a short time after the system was installed, the frames were manufactured within VW’s strict tolerances. A clear advantage over manual production.

The two GEO stations for add-on parts are a project-specific highlight in the sophisticated Amarok GEO line. In these stations, 34 parts of varying size and complexity must be inserted in a geometrically correct fashion and welded. To start with, an operator loads all the parts into undocked robot grippers. The tight space requirements and legal safety standards were successfully met thanks to new KUKA SafeRobot technology. In each of the two GEO stations, a 500 kg heavyduty robot uses a large multiple gripper to move several of the components to the fixture, which weighs up to four tons. The ladder frame is then inserted via a third gantry and the first welding tasks are completed. This is followed by a further highlight of Amarok production: a heavy and highly complex geo multi-gripper is picked up by the handling robot. This gripper must be moved to two different positions in an extremely confined space. While the components are being welded, the gripper stays firmly secured to the fixture until the add-on parts that it holds are joined with the proper dimensions. Next, four welding robots and a four-ton KUKA turnover positioner ensure that even seams in hard-to-reach welding positions can be welded with optimal quality.

After the GEO line, a range of feeding and fetching tasks are performed in the finishing area by a 500 kg robot mounted on a KUKA linear axis. This robot has to move the 230 kg ladder frame between the buffer, punching, gauging and visual inspection stations before it is handed over to a power & free conveyor system. It only takes a few minutes to finish joining and processing a frame before it is coated in a cathodic dip painting (CDP) system.

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