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Automation Technologies 4/2015

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Automation Technologies 4/2015


SENSORS AND MEASUREMENT RFID system and sensors offer considerable advantages in an assembly plant for injector nozzles Achim Weber 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 RFID system and proximity switches which detect aluminum workpiece carriers on the conveyor belt. Achim Weber is a sales specialist at Turck, Mülheim, Germany Injector nozzles for injection systems basically consist of a nozzle tip, the needle with a spring seat, a spring, sleeve and a type of cover that encloses the entire unit. Mounting them is a complex process since components of each individual injector nozzle are all separate parts. This makes each injector unique. The needle or spring of one nozzle cannot simply be refitted on another nozzle without a loss in quality. Many nozzle components, from the spring seat to the spring, right through to the individual ground needle, have to be measured precisely and matched with each other. The assembly of these unique nozzle products is fully automated on the conveyor belt. This type of assembly is made possible by special machine builders such as Sonplas GmbH from Straubing. The company specializes in assembly and testing equipment for car parts suppliers. Based in Lower Bavaria they have made a name for themselves in the sector, with machines that assemble or test supplied parts through which fuel later flows in the vehicle. Many international car parts suppliers appreciate this expertise with almost 200 employees with this know-how. About Company name: Hans Turck GmbH & Co. KG Headquarters: Mülheim an der Ruhr, Germany Turnover: € 470 m (2014) Group Employees: 3 500 (2014) Products: sensor, fieldbus, connection and interface technology, human-machine interfaces (HMI), RFID systems for factory and process automation RFID read/write heads and uprox+ proximity switches are fitted at each individual station of the assembly line; the tag is fitted directly in the aluminum workpiece carrier

SENSORS AND MEASUREMENT At the end of 2012 Sonplas won the order to design and build two machines for assembling injector nozzles. “The special feature of these machines was the fact that measuring was carried out in front of each assembly station and then the workpiece machined according to this measurement,” Sonplas sales manager Hermann Pankofer explains. 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 was ultimately able to meet this set of requirements. Other proximity switches do Sonplas had to meet high requirements in terms of precision and repetition accuracy for the assembly of injector nozzles not manage to guarantee such a large switching on aluminum with the same level of reliability. The 4 mm switching distance of the NI4U-EG08-AP6X used is considerable for a sensor in the M8 housing – and is the same for all metals. Sonplas fitted 56 sensors in each of the two assembly machines. They The fact that the Turck sensor detects aluminum so well was a major benefit for us. This saved us having to implement any labor-intensive alternative solutions. Manuel Lehner, Sonplas detect the workpiece carrier on the conveyor belt, control stop and positioning operations, are used for detecting jams and initiate read/write operations. Communication via Profibus The test data at the individual measuring stations is linked with the ID number on the tag via the RFID read/write heads and stored in a database. The data reaches the database of the machine via Profibus using Turck‘s BL67 gateway. “The challenge with this machine was to maintain a tolerance below one micrometer while coordinating the high-precision measurements and the equally precise assembly operations. This also had to be repeatable in a continuously running production plant. Everything is coordinated here, each cog interlocking with another one,” project manager Lehner sums up the particular requirements of the assembly plant and adds: “Here we must be able to rely on each component installed – and naturally on each sensor – one hundred percent.” AUTOMATION TECHNOLOGIES 4/2015


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