.jpg">One of the world’s largest merchandisers of tea manufactures, fills and packages selected tea blends from all over the globe. In a move to enhance their product, the company decided to abandon the use of foil packaging for tea cartons and changeover to other materials to seal in the flavor. Such a change made it necessary to rethink the control concept for the existing packaging and transport system.The operation is large for such processes, spanning some 250 feet and functioning as a link between 20 automatic filling machines and the final packaging station. Before the tea specialties, such as rose hip, peppermint, and chamomile teas, are transported to the final packaging station by the conveyor line, it is necessary to seal the cartons using a carton sealer.While the filling system is operating, cartons are folded and glued in carton aligning stations. The finished cartons are then transported to the filling machines via a clever carton logic system resembling a shunting yard. The various tea specialties are sorted into the arriving packages at the filling machines.Multiple light barriers, valves and motors help control this fully automatic process.CONTROL SYSTEMA PC controls the carton sealer utilizing the standardized IEC 1131-3 programming language. This type of program is based on high-level languages and permits the user program to be represented in a manner familiar to any PLC programmer, for example – as a standardized instruction list, ladder diagram or function block. The final packaging station is also controlled by INTERBUS.INTERBUS smart terminal I/O modules pickup the signals from the jam light barriers as well as the contactors which are also decentralized and used for activating the conveyor belt motors.In addition to the INTERBUS I/O modules, a large-sized text display system is also integrated into the bus topology via an integrated INTERBUS interface.INTERBUS CMD (Configuration, Maintenance and Diagnostics) software clearly displays INTERBUS system information. In order to guarantee packaging quality in the case of a conveyor jam, for example, it must be possible to switch-off inpidual belts within a specific time, working back from the location of the malfunction. Switch-off is done through CMD, and the conveyor restarts automatically and runs normally following correction of the malfunction.PREVIOUS SOLUTIONThe old, conventional contactor control system was initially replaced by a PLC in order to achieve the required level of flexibility.

Tea cartons reach the final packaging station, which is also controlled by INTERBUS.

RESULTS/BENEFITS SUMMARYFor reasons of time, the usually complex and cost-intensive parallel cabling was replaced by a modern automation system based on INTERBUS, greatly reducing the amount of cabling required, as well as the related labor and material costs. INTERBUS also made possible the separate, time-saving testing of each prefabricated, decentralized subdistribution boards.INTERBUS support of the decentralized contactor scheme also saved considerable implementation time, one of the principal reasons for this company’s decision to adopt INTERBUS as its networking standard.