RFID Identification of Injector Nozzles

Sonplas uses Turck's BL ident RFID system and uprox+ sensors in an assembly plant for injector nozzles

Special machine builders Sonplas developed and built two machines for assembling high-precision injector nozzles. To meet customer requirements in terms of precision and repetition accuracy, the individual nozzles and their components must be identified accurately in the process. For this Sonplas uses Turck's BL ident RFID system and uprox+ proximity switches which detect aluminum workpiece carriers on the conveyor belt.

  • Turck RFID read/write heads and uprox+ proximity switches are fitted at each individual station

  • The tag is fitted directly in the aluminum workpiece carrier

  • Sonplas had to meet high customer requirements in terms of precision and repetition accuracy  

  • The reader reads the tag on the workpiece carrier in order to identify the individual components

  • The data of the read/write heads reaches the database using Turck's BL67 gateway with RFID modules

At the end of 2012 Sonplas won the order to design and build two machines for assembling injector nozzles. The machine firstly measures the force of the spring at a station and then presses the spring seat according to the measuring results. The spring is then placed on the needle and another machine checks the height of the spring at a defined counter force. The height must be measured with a tolerance less than 1 micrometer, since the strength and the seat of the spring later influence the injection action of the injector nozzle in the engine.

Assembly process requires traceability
The complex coordination of measurements and assembly processes requires the relevant measuring data to be tracked and assigned uniquely. “Each component is tracked, not only the injector nozzle in its entirety, but also each individual part itself,” says project manager Manuel Lehner. In order to assign the components to a nozzle, they move on the workpiece carrier of the nozzle. The workpiece carrier specially optimized for the plant provides a separate place for each required injector component. RFID readers read the tags that are fitted on each individual workpiece carrier.

For the assembly machines Sonplas looked for an RFID system that can be mounted compactly in the machine. “The problem was not so much the large read/write distances involved but the fact that the tag had to be fitted directly on the aluminum of the workpiece carrier,” Lehner describes. The ideal tag could be found in the extensive portfolio of the Turck RFID system: Turck's TW-Q25L12,5-M-B128 tag – not much larger than a thumb nail – meets all the requirements. Eleven TN-M18-H1147 read/write heads in an M18 threaded barrel are fitted in each of the two machines in order to identify the workpiece carriers.

Long switching distance on aluminum
Sonplas looked for inductive sensors as initiators in order to detect the material carriers on the belt and to check the correct position of the workpiece carriers for the tags to be read. This required a compact switch with a long switching distance on aluminum. Only an uprox+ sensor from Turck was ultimately able to meet this set of requirements. Other proximity switches do not manage to guarantee such a large switching on aluminum with the same level of reliability. The four millimeter switching distance of the NI4U-EG08-AP6X used is considerable for a sensor in the M8 housing – and is the same for all metals.

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