RFU630 UHF interrogators from SICK
have been installed at the Mercedes-Benz plant in Rastatt for trouble-free and reliable identification of car bodies of the Mercedes B Class model.
The KTL-Trockner 2 is the cathodic dip painting drier at the Mercedes-Benz plant. In an environment, which is extremely unfavourable for RFID systems, the RFU630 UHF interrogators (write/read units) from SICK have proved their mettle in automotive body identification.
For process-reliable handling of the car bodies, it is essential to detect reliably behind the drier whether the item at hand is a car body of the new B Class that is already undergoing preparation for production. In the event of ‘no reads’, the conveyor system stops and the result may be a reject. If reading errors take place, there is risk of confusion, resulting in the feeding of incorrect car bodies, the danger of collisions during car body handling, or misdirection of the car body.
Process segment surface makes maximum demands on RFID
When selecting the right RFID solution, the most difficult to read ‘i point’ defines the performance requirements for the interrogators. At Mercedes-Benz in Rastatt, this identification point is located at the conveyor system behind the KTL-Trockner 2. After pre-treatment, through degreasing, rinsing, and phosphating in enormous spraying facilities and cathodic dip painting, the car bodies are dried in kilns at temperatures of about 180°C, following which, they are made available in any order on a skid conveyor section in three lines for the next processing stages.
The area behind the drier including walls, ceilings and floors to the conveyor system and numerous car bodies, is pure metal, causing stress to many RFID systems as the high-frequency reflections from the facility can substantially impair data transmission between the transponders and the interrogators.
RFID system from SICK
SICK’s RFU630 UHF interrogators have proven their worth on 24 identification points in the surface where the environment makes the highest demands on availability and reading reliability. The RFU630 interrogators are integrated at the plant into PROFIBUS-DP via external CDF600 fieldbus modules.
Another aspect also favouring the RFU630 interrogator is easy parameterization and operation with the aid of the SOPAS programming software. In case a device has to be replaced, parameter cloning by means of SD micro card minimises the time and expense required.
In order to achieve maximum reading reliability in the metal environment behind the KTL-Trockner 2, the maintenance technicians at Mercedes-Benz and the application specialists from SICK have implemented an ‘identification point-specific’ parameterization of the interrogators. In each case, the reading range was reduced to the actual distance to the transponder (0.4m to 1.2m). Both the output performance and the receiver sensitivity were optimised in this way.
Reading takes place when the car body stops briefly, helping to achieve largely constant environmental, and transmission and reflection conditions. For reliable reading and writing, functions were shifted into the device and, for diagnostic reasons, implemented partly on the jointly developed function block.
SICK’s RFU630 interrogators have been able to deliver a confirmed reading reliability of more than 99.98% in car body identification.