Contrinex photoelectrics are a ‘sweet’ solution for detection in packaging

During confectionery packaging operations, conveyor lines deliver preformed cardboard cartons to packing stations. At each station, a pick-and-place packing robot packs layers of bagged candy in cartons. Once filled, cartons are conveyed to case-sealing stations. A highly reliable retro-reflex photoelectric sensor, mounted beside the line, senses each carton as it arrives at the packing station, halting the conveyor and initiating the packing sequence once it is correctly positioned.


In the confectionery manufacturing industry, secondary packaging is usually required when preparing multiple product packs for wholesale distribution. In high-volume production, manufacturers pack sealed bags of candy in cardboard cartons, which are in turn stacked for shrink- wrapping and palletisation.

Preformed cartons arrive at the packing station in a continuous stream. Once the leading carton reaches its designated position, the conveyor halts and the packing sequence commences. A pick-and-place robot lifts successive layers of bags and lowers them into the carton. Once the predetermined number of bags has been packed, the carton is conveyed to a sealing station.

If a carton stops in the wrong position, or if no carton is present, the packing sequence must be inhibited to prevent damage occurring. A non-contact sensor system is needed to detect the position of the leading carton as it arrives at the packing station, halting the conveyor and initiating the packing sequence once. It must be reliable and require minimal maintenance.


Miniature retro-reflex photoelectric sensors from the Contrinex C23 range are ideal for this application. Used in conjunction with a 41mm-diameter reflector, these sensors have an operating range of up to 4500mm – more than adequate for the task. A single sensor is mounted beside the carton conveyor, immediately before the packing station, with the reflector positioned on the opposite side. As the leading carton breaks the light beam, the sensor detects its presence and halts the conveyor in the correct position for packing.

Mounted in 20mm x 30mm x 10mm miniature plastic housings, C23 photoelectric sensors  are available with industry-standard PNP or NPN 3-wire or 4-wire output. Connection to the customer’s control system is via a PVC-sheathed cable with the choice of an integral M12 connector or a hermetically sealed entry. A second output provides a stability alarm in the event of reduced sensitivity, flagging the need for preventative maintenance before any performance degradation occurs.

A custom-designed range of multi-position mounting brackets allows systems engineers to locate sensors optimally in almost any situation. The C23 range detects slow- or fast-moving targets reliably. Remote selection of switching frequency is possible via IO-Link, a standardised point-to-point serial connection protocol, available as standard at no extra cost for PNP versions.

Contrinex sensors are available from PLUS Automation.

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