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Case Studies Of Industrial Robots

Robots in action can be found everywhere. Robot Manufacturers give examples of robot applications in different industries.

Dürr Systems, Germany - IFR-Partner

Electrostatics Redefined - a New Atomizer Generation for More Performance with Less Complexity

One does not have to think far back, when the world of the application technology in the car body painting was still two-part. It was common to use air atomizers for the interior painting and the second base coat application on exteriors, for all other exterior surfaces high-speed atomizers with electrostatic charge. The disadvantages of this split: high paint overspray losses from the air application, various systems and processes in one line, lacking flexibility. Since this time, a lot has changed. Almost all OEMs carry out the second base coat application with the effective electrostatic application. This process, called bell/bell process in trade language, has become state of the art by now. Now the question arose whether the electrostatic application technology can also be used for interior painting. The answer: basically yes, but with two conditions that have to be met. Firstly: the atomizer must be compact, in order to guarantee a reachability of all surfaces to be coated and secondly: the spray fan width must be adjustable in a wide area. Ideally, this atomizer should not only be usable for interior painting, but also for exteriors.

So far the targets. The Dürr product developers converted these targets into reality with a high priority. The high flexibility of the fan pattern variation is achieved already with the HD and HX types of the EcoBell2 by means of a bell disk shaping air system that has two shaping airs independent of each other. The compact atomizer is a far more challenging demand, however, particularly in the application of waterborne paints. An exterior charge with the electrode ring in the previous form is not usable because of its size and for a direct charge of the paint material, a voltage block is necessary. This fact recently led to the development and the use of various systems. Here, the variant diversity ranges from canister technology via docking systems, systems on pig basis, to the voltage block with the aid of dosing cylinders which are installed on the robot arm. On closer inspection of the different systems one discovers, however, that no system meets the requirements made to the waterborne paint application equally well. They are for instance either restricted in their efficiency, not really suitable for interior painting because of their size or too complex and this way too expensive.  Only the exterior charge offers a high efficiency with low complexity. To make this principle usable for interior painting was the starting point for the development of a new atomizer generation, the EcoBell3.

A new atomizer generation - for Dürr this is not simply another version of the EcoBell2, but a completely new atomizer. Of course, its efficiency surpasses that of its predecessor by far. Its new features which are to be presented at a later time will not only lead to minimum color change losses and short color change times, but will offer new process-specific options. The most important (aspect), however, is: the EcoBell3 is equally suitable for interior and for exterior painting. This was achieved by a very compact electrode ring. This way, this atomizer represents the ideal synthesis between high performance and process flexibility on the one hand and lowest complexity on the other hand.

 

An absolute novelty: the interior painting with a high-speed atomizer and exterior charge. Possible with the EcoBell3, the new atomizer generation by Dürr

Exterior application with the EcoBell3: high performance, low complexity

What does the use of the EcoBell3 now actually mean for the customer in the practice?  In one of the first projects with this atomizer for a sports car manufacturer, the intended capacity of the installation demonstrates this, the interior inside and exterior painting is combined summarized in one zone. The advantage resulting from that is considerable: a significant reduction in installation length and the number of robots and thus a reduction of invest and operating costs. If a distribution of the interior and exterior painting scopes to several zones is necessary, and this is certainly the normal case in a paint shop, the workloads can be distributed to all robots if the EcoBell3 is used in such a way that an optimum workload will result. Besides, the degrade functionality is possible here. This means that the other active robots can take over the painting scope if one robot should fail. A function that eliminates the need for so-called backup zones with manual application superfluous Also, installation length and operating costs are reduced significantly here.  Small cause, great effect.

The future requires flexible manufacturing concepts more than ever. In the field of paint application it is now absolutely feasible to divide up the previous, little flexible concept of a painting line into individual zones and to arrange these in parallel. This so-called "box concept" offers interesting possibilities: only two robots are required to completely paint the vehicle. Completely in this context means with primer, base coat and clear coat, exterior and interior. What is already possible today from process-specific view by the introduction of 3wet painting processes that manage without intermediate drying can now also be realized with the EcoBell3 from view of the application technology. The effect in this case: a clear reduction of the color change losses. And since the transportation between the individual paint applications is eliminated, this means that the part of the process time increases in relation to the entire cycle time. Speaking of cycle time: in a painting line it is determined by the biggest vehicle. Not so with a box concept. Here, an individual cycle time adapted to the vehicle size and the process can be operated in every box. This way, the capacity of the entire system can be increased which leads to reduced unit costs. At last, an increasingly important advantage of this concept in the present time should not remain unmentioned, the flexibility with regard to the system capacity. For instance, the capacity of an installation can be increased in stages according to this concept by the installation of additional boxes. Also, it is possible to react to workload problems by turning off individual boxes.

 

The EcoBell3 provides interesting, highly-flexible layout possibilities, e.g. the box concept. Complete painting with only two robots possible, individual cycle time depending on vehicle size, process and painting scope, flexible adaptation to capacity requirements by turning individual boxes on/off.

 

But now back to reality: an important area of application for the EcoBell3 will become the bumper and plastic add-on parts painting. From the application viewpoint, the bumper unites the exterior and interior painting in one component. Large surfaces must be covered just the same as detailed areas with a partially very complex geometry which can only be achieved with plastic parts for reasons of production. The painting process is complicated by the fact that the individual parts are usually positioned close to each other on the product carrier and into the bargain, the cycle times and time on part are very limited. What does all that mean for the application? A compact, efficient atomizer with a high flexibility concerning the spray pattern configuration with the possibility of continuous painting without interruption. The EcoBell3 fulfills these conditions without any ifs and buts.

Bumper painting with the EcoBell3. Here the high flexibility is proved: wide pattern for large surfaces, narrow cylindrical pattern for detailed surfaces. Tight areas require a compact atomizer.

 

Let us have a short look on the "painting robot" overall system. This consists of the robot itself and the integrated application technology. Integrated is to be understood literally here. No additional valve and application cabinets are required. Together with the new linear paint color changer, the EcoLCC and the compact dosing pump, the robot has a very slim arm. Ideal for applications with a reduced accessibility. As already described in detail, the application technology is designed for all painting jobs. A high transfer efficiency and minimum color change losses are the important features of this simple and compact overall system.

 

The overall system for the electrostatic application of waterborne paints by Dürr. Simple and compact. The features: EcoBell3, integration of the entire paint application in the robot, slim robot arm with linear color change system of EcoLCC and dosing pump for minimum color change losses and color change times.

 

The examples of this contribution show with great clarity which importance the atomizer has for the painting process. The EcoBell3 offers many advantages and possibilities, last but not least it makes a clear contribution to the efficiency in the handling of energy and resources. This is by the way also this year's motto for the Dürr Open House event that took place in March 2010.

 

Literature:

Schumacher, Hans: Redesign in the application technology - more performance with less complexity. Automotive Circle International, Bad Nauheim, 16-17 November 2009 Automotive Circle International, Bad Nauheim, 16.-17. November 2009

Svejda, Pavel: One atomizer for all cases - short painting lines due to new application concept. Journal für Oberflächentechnik / Journal for surface technology, JOT 9, 2009

 

Author:

Dr.-Ing. Pavel SvejdaDürr Logo
Dürr Systems GmbH
Carl-Benz-Straße 34
74321 Bietigheim-Bissingen

Phone:  + 49 (0)7142 78 2290
Fax:      + 49 (0)7142 78 2107
E-mail: pavel.svejda@durr.com
Internet: www.durr.com