The increased usage of new materials in automotive production brings with it a particular challenge in terms of dryer design. This was the reason behind the construction of what is undoubtedly one of the world's longest CDP-dryers (CDP = cathodic dip-painting) at the BMW plant in Dingolfing.
240 meters per line
SAR was commissioned to deliver the control system for the 2-line dryer - with each line measuring 240 meters in length, including the A-sluices. Measurement technology and control engineering are two areas that pose particular challenges when it comes to constructing a dryer of these proportions.
One dryer for all models
Not only was it necessary to consider the fact that the various materials used for the vehicle bodies exhibit different heating and thermal behaviour, it was also important to observe the individual specifications given for each vehicle model.
For these purposes, the dryer is divided up into different process zones, through which the exceptionally lengthy (approximately 215 meters long, in fact) support chain conveyors pass when travelling along the drying tunnel. This allows for a relatively slow and gentle heating-curve. Following the drying process are 80-metre-long cooling zones whose incrementally decreasing temperatures cool down the vehicle bodies gradually.
Scope of delivery from controller to conveyor system
SAR supplied the controls for the process technology used by the two parallel lines of this innovative CDP-dryer, as well as those for the technical building services (TBS). The delivery also included the entire control technology for the conveyor system beginning from the feed lines of the CDP area, the internal conveyor system through the dryer and the cooling zones, as well as the external conveyor system used by the empting storage section and the return tracks back to the pre-existing production areas.
The control system was built using a total of 7 SIMATIC S7-400 with CPU416F-3 PN/DP. Zenon was used for the visualisation software.
Assembly of the new dryer began during the summer of 2013, with production operations starting in December of the same year. The system has been running for about a year with great success.
The CDP dryer provides an excellent means of overcoming the heating and thermal behaviour-related challenges posed by the new composite materials that are finding increasing application in automotive manufacturing.
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Connection empting storage - dryer
One of the many switchboards used by the dryer, with the clean gas pipeline in the background