KUKA Robots Grind and Polish Lids for Pressure Cookers and Cooking Pots for WMF

In an ultramodern, future-oriented system from SHL Automatisierungstechnik AG,WMF AG has turned to KUKA robot technology for grinding and polishing processes. The synchronized KUKA KR 60 robots give the inner surfaces of lids for pressure cookers and cooking pots a matte finish, while polishing the outer surfaces to a shine. The system provides the company with a state-of-the-art facility for surface finishing of the aforementioned products

WMF AG (Württemberg Metal-goods Factory), with its headquarters in Geislingen an der Steige, Germany, was founded in 1853 and sees itself as a provider of branded products which must be able to meet the most rigorous of demands in terms of design, quality and ergonomic functionality. The company currently has a workforce of around 3,500, with some 2000 at the headquarters in Geislingen alone.

Additional plants are located in Hayingen and China. WMF AG supplies an extensive range of products, with the principal focus on table- and kitchenware,for both commercial and domestic use. Products are sold in WMF’s own retail outlets, specialty stores,epartment stores, furnishing houses and selected mailorder companies. Outside Germany, WMF has a network of distributors in Europe, USA and Japan.Of late, KUKA robots have been taking a shine to pot lids – literally – grinding and polishing them in WMF’s new ultramodern system.Until now, the manufacture of cooking pots and pans has been dominated by turntable systems. As these have meanwhile become very maintenanceintensive,however, the company has now embarked upon a modernization course for the manufacture of lids.

The system concept from SHL Automatisierungstechnik AG is based on four robotic cells. The first consists of a handling robot with a camera system and a grinding unit for the inner surface finish of the lid.In three further cells, each consisting of a handling robot, a grinding unit and two twin-shaft polishing machines, the outer surfaces are polished to a shine. The KUKA robots are each fitted with an external axis in order to be able to carry out the finishing work on the inner surfaces of the lids with a greater rotational speed.

“To manufacture these parts on the conventional turntable systems, we used to have to carry out two separate operations for the inner and outer surface finishing processes, each with a total of eight clamping fixtures. The new system allows production that is significantly more cost-effective,” says Helmut Kamitz, Head of Production at WMF AG.

The decisive advantage of the new robotic system compared with a turntable is that each robot can perform precisely specified motions at the individual brushing and polishing discs, derived from the specific shape of the individual lid, and can thus achieve an optimal surface finish in the shortest possible time. Since all settings are saved in the program, reproducibility is assured.Polished side up The pot lids roll into the system on a conveyor belt. The position and orientation of each lid are detected by an integrated camera system and passed on to the KR 60. The robot then lifts the lid off the conveyor using a vacuum gripper and guides it to a so-called “Scotch belt”. In a very short time, this roughened belt endows the interior of the unprepossessing raw product with the matte finish typical of the inside of lids.

“We call this the ‘solar finish’,” explains Helmut Kamitz. Once the lid has received this finish, the first KUKA robot passes it directly to one of its three colleagues, in turn, which now polishes the outer surface. The first KUKA robot has the fastest cycle time. “Since it only has one task to perform,”explains Gerd Lehr, Director at SHL Automatisierungstechnik AG, it is three times as fast as its synchronized colleagues. It can thus always provide a new product to the KUKA robot that has just completed the outer surface finishing process.

The polishing paste is supplied directly from a central tank to the individual units where it is then precisely dosed and carefully applied to the polishing disc and to the product via a dispensing gun.The robots now process the lids with the special polishing discs until they achieve the gleaming high-quality WMF finish. The company places great value on the high quality of its products. The requirements are specified in a quality standards description.