Posted to News on 18th Oct 2024, 13:30
Background-suppression photoelectrics know when the box is only half-full
In a secondary packaging operation, bags of products like confectionery are often 'shingled', a process of layering them into a cardboard shipping box in alternating overlapped layers. Photoelectric sensors with background-suppression from Contrinex have provided a reliable means of checking the correct quantity of bags in each box.
In the application, a multi-axis pick-and-place packing robot picks and lifts a row of bags and layers them into a shipping carton. The sealed bags of sweets are gusseted and have triangular profiles. The robot alternates the orientation of the layers so that they overlap each other, optimising space utilisation within the carton. Once the predetermined number of layers has been packed, the carton is conveyed to the sealing station before palletisation and dispatch.
Occasionally, an incorrectly formed layer occurs, where a bag might be missing from a row, or damaged or misaligned. A reliable sensor that requires minimal maintenance is needed to detect the height of the top layer of bags, ensuring defective cartons are not despatched.
Contrinex's C23 family of photoelectric sensors is small but powerful. They offer a wide range of sensing technologies in a choice of stainless-steel or plastic housings. The plastic versions' robustness and affordability make them popular for conveyor and packaging applications.
The sensor provides a long sensing distance for such a small background suppression sensor, which enables it to be mounted centrally above the conveyor. As each carton passes below on its way to the sealing station, the sensor detects the top surface of the packed bags. If the top layer's height falls outside preset limits, the sensor triggers a reject mechanism that diverts the carton to a holding area for investigation.
The sensor's 15 mm to 250mm operating range accommodates various carton sizes without repositioning it. In applications requiring sensor adjustment, versions are available that provide simple electrical adjustment via an onboard potentiometer, teach via setting buttons, or remote adjustment via IO-Link. IO-Link is a standardised point-to-point serial connection protocol provided at no extra cost on the PNP versions.
The sensor was mounted using one of the C23 family's custom-designed multi-position mounting brackets. Because the application is a secondary packaging line, where the confectionary has already been packaged into bags, the lower-priced plastic version of the sensor was suitable and is still ECOLAB-approved.
The customer chose a sensor with a 2m PVC-sheathed cable, but integral M8 connector versions are also offered. All C23 sensors offer a Stability Alarm function within the suite of IO-Link-accessed tools. This feature flags, in the event of reduced sensitivity, the need for preventative maintenance of the sensor, for example, cleaning the lens or realigning the sensor, before any performance degradation occurs. The Stability Alarm is also available as a switched second output pin or wire, giving access to this powerful feature without needing IO-Link.
The C23PA photoelectric sensor family offers the widest range of sensing technologies, including the unique UV-light-based transparent-object detection.
