Increasing effectiveness through fully automatic car painting

For many years, painting machines and manual painters shaped the picture in the serial painting of car bodies. For external surfaces, the painting machines were used; internal surfaces such as door entrances were the domain of the manual painters.

To coat the body with the three paint coats primer, base coat and clear coat at separate coating stations each, up to 30 atomizers in the external area and approximately 15 atomizers for the manual painters were often necessary. In manual painting and in the second application of metallic paint, the paint was atomized with air atomizers, which showed a low efficiency, compared with the electrostatic atomization in the external area.

Driven by the desire for more flexibility and effectiveness, the introduction of robots instead of the painting machines and the automation of the interior painting with robots began in the 90s.

The increase in flexibility with increasingly more frequent model changes and modified vehicle design could only be achieved with robots. It is the task of the robots to guide the atomizer at a constant distance and at right angles to the body surface (approximately 200 mm) during the painting. For this, the painting paths and the different brushes of the painting are determined in specific programmes at 3D models of the bodies to be coated. These data are transmitted to the robot controller. This way, the motion processes during the painting are almost completely defined. The teaching of the robot is only necessary at difficult places and for fine tuning.

Higher effectiveness resulted from two factors — on the one hand from the reduction of the number of atomizers by approximately 30-40 percent compared to the painting machines, on the other hand from the improvement of the transfer efficiency. For the latter, high-speed rotating atomizers are used for interior painting as well as for the second coat of metallic paint.

The fully-automatic painting with robots is both interesting for new paint shops — so-called greenfield plants and for the replacement of painting machines of former years (brownfield plants). While in the case of greenfield plants, the capital expenditure may be of great importance among other things and may be significant for the design of the painting installation, the integration of the robots into the spray booth already available there and the expenditure combined with that are decisive for brownfield plants.

Robot Generation

As a leading system vendor for car paint shops, Dürr has been producing painting robots that were developed especially for this task since 1997. Far more than 3000 Dürr robots are being used worldwide today. In 2005, Dürr launched the first robots of the new EcoRP robot generation, particularly aiming at the replacement of older painting machines in the exterior painting of bodies. The company introduced further members of the family of the new EcoRP robot generation in 2007, on the occasion of the in-house exhibition ‘Open House’ organised every two years.

These painting robots for the exterior and interior painting, handling robots for door and hood opening and clean wall travelling rails can be used in spray booths adjusted to the respective requirements and allow to perform any painting job in car body and add-on parts painting.

The consistently realised modular design allows using the painting robot with various adaptors as a free-standing unit or on travelling rails. The travelling rails may be installed in an elevated position or close to the floor in the booth. The handling robots for the hood opening are based on the painting robot; here the atomizer is replaced by a handling tool. At the Scara robots used to open the door, identical drive units are used.