Small but powerful photosensors help wrap chocolate

In factories producing fast-moving consumer goods, automated packaging operations are the norm. Confectionery products are no exception; in high-volume production, manufacturers pack sealed bags of candy in cardboard cartons, which are in turn stacked for shrink- wrapping and palletisation.

Packed cartons arrive for shrink-wrapping in uniform stacks. A wrapping machine encloses each stack in a tube of heavy-duty heat-shrink film; the stack then passes through an infrared oven, where the film shrinks, forming a sealed pack of cartons. After heat-shrinking, packs are conveyed to the consolidation area for palletisation.

Factory operators need to monitor production throughput for each packaging line. Manual counting methods are impractical and expensive. A highly reliable non-contact sensor system is needed to detect the presence of each pack as it leaves the shrink-wrapping area and to update the item count held on a plant-wide control system. Long-distance operation is desirable, as not all packaging lines are easily accessible markings as cartons leave the printer-applicator, rejecting any defective cartons.

The miniature through-beam photoelectric sensors from the Contrinex C23PA range are ideal for this application. These dual-unit sensors, available with an optional alignment aid, have a maximum sensing range of 30m. Each sensor comprises a separate transmitter and receiver, each mounted in a 20mm x 30mm x 10mm miniature plastic housing; connection to the control system is via a PVC-sheathed cable with the choice of an integral M12 connector or a hermetically sealed entry.

Immediately after each oven, a sensor is mounted with the transmitter and receiver on opposite sides of the conveyor. Depending on the space available around the oven, either unit may be located some distance away from the track. The integral alignment aid ensures rapid, accurate set-up, even at extremes of operating range, while the choice of mounting brackets allow optimal sensor positioning in almost any situation.

As each carton breaks the light beam, the sensor detects its presence and signals the control system to increment the item count. Industry-standard PNP or NPN 3-wire or 4-wire outputs support direct interfacing with modern industrial controls. A second output provides a stability alarm in the event of reduced sensitivity, flagging the need for preventative maintenance before any performance degradation occurs.

The C23 range detects 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.

A sensing range up to 30m, for these Through-beam sensors is adjustable via a teach button or via IO-Link, accommodating a wide range of machine geometries. Sensitivity parameters are stored on the sensor’s inbuilt memory and may be retrieved or updated remotely via IO-Link, eliminating the need for manual adjustment and so unplanned sanitisation is avoided.

Mounting the sensors is simple and low cost, thanks to a custom-designed range of multi-position metal mounting brackets and protective sleeves.

Contrinex sensors and more information are available from PLUS Automation.

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