Photoelectric sensors make packaging ‘easy-cheesy’

When a manufacturer of individually packaged cheese portions, operating a high volume production facility, needed a method of reliably detecting the presence of each cheese portion as it leaves the buffering area, and triggering the packaging station, it turned to Contrinex.

The production process cuts cheese portions to size and sends them along a conveyor to the packaging station. Prior to packaging, a buffering station regulates the flow of the cheese portions to give a predetermined spacing to suit the packaging machine’s throughput, which depends on the dimension of the cheese portion being produced.

To synchronise the packaging operation with the buffering, a sensor is required that will reliably detect each cheese portion, irrespective of its size, colour or texture, whilst ignoring the conveyor it is travelling on.

The hygiene standards of the facility require a ‘food-grade’ certified sensor that can withstand the aggressive cleaning agents used during the frequent washdown routines. The sensor must be adjustable remotely, removing the need for manual adjustment, as this would necessitate cleaning and sanitisation, plus as is typical for food packaging, maximising throughput is a priority.

The Ecolab-certified, background-suppression diffuse photoelectric sensors from Contrinex’s C23PA product family provided an ideal solution. The small cubic sensor is mounted using its low-cost stainless steel mounting accessories, high above the product conveyor because of its 300mm sensing range. It is placed immediately after the buffering station and triggers the packing operation when it detects the presence of the cheese portion passing underneath.

In addition to the standard PNP, normally-open output and M8 connector, the IO-Link communication protocol for sensors is utilised for configuration between production runs. Rather than using IO-Link, the optional second switched output is used for the preventative maintenance ‘stability alarm’. This output is switched on if the sensor detects reduced performance, for example, due to the lens being contaminated, which flags the need for preventative maintenance well before detection is degraded, and so before the machine starts misbehaving.

As well as offering configuration over IO-Link, the sensors offer a choice of one- or two-step teach procedures which simplifies the initial set-up. The teach operation allows the process engineers to teach the target object and the conveyor belt, each time a new portion size is introduced. Once taught, sensitivity parameters are stored on the sensor’s inbuilt memory and may be retrieved or updated remotely via IO-Link, eliminating the need for future manual adjustment.

The small (20 x 30 x 10mm) but robust sensors are rated to IP67 and are approved by Ecolab for being able to resist cleaning with harsh food-grade cleaning chemicals. They also benefit from a choice of low-cost stainless-steel mounting accessories and protection bracketry, which have helped the reliability of these sensors in the application to be excellent.