Sensors for packaging

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Wet environments, harsh conditions, limited space, everything needs to happen very quickly. We're talking about packaging and filling systems. Efficiency, reliability and cost effectiveness have top priority here. A true challenge for the sensors and their manufacturers. Leuze electronic is well positioned, as this article shows using selected case studies and sensor solutions.

Packaging machines can fill, close, wrap, shape or even print. An enormous range of applications, whereby sensors from Leuze electronic are used throughout. There is a nearly endless variety of packaging and packaging materials – whether foil, cardboard, glass, paper or metal, high-gloss or structured, opaque or transparent. The detection of transparent media particularly is one of the supreme disciplines in sensor technology. 

With the 3B, 55 and 18B series, Leuze electronic offers an entire line of sensors specifically for this purpose. With robust housing, small dimensions, short response time, high switching frequency and a tracking function for extending the cleaning interval (50x), the 18B series holds a prominent position here. Thanks to these features, even highly trans-parent containers can be reliably detected in liquid filling systems. Foils are very common for primary and secondary packaging and pose no problems for these sensors, regardless of whether fast-moving, small, thin or transparent objects need to be detected. Due to the high safety classes, they can also be used in extreme environmental conditions.

For filling systems, very special requirements need to be taken into account that are particularly demanding on the used sensors. Essential here are smooth, fault-free processes as well as ensuring the quality – all in the hygienically challenging wet areas of the system. To monitor the filling of containers, so-called water sensors of the 55 series are used, such as the LS 55, a compact, stainless steel, throughbeam photoelectric sensor in WASH-DOWN design for wet areas with degree of protection IP 67 / IP 69K. It is used wherever containers (glass, PET, transparent or colored) are filled with liquid, whereby even opaque containers with plastic labels are transilluminated.

Industrial cheese production and packaging is one of the most demanding areas of application for sensors (title figure). "This is due, on the one hand, to the damp, often even wet environment with very high salt content and, on the other hand, to the frequent cleaning and disinfection intervals required to keep the production systems germ-free," explains Manfred Hinrichsen, the director operational and electrical engineering at the DMK plant in Nordhackstedt. The PRK 55 retro-reflective photoelectric sensors and HRTR 55 light scanners of the 55 series were designed specifically for such requirements.

The sensors have a housing made of V4A (AISI 316L) high-quality stainless steel. In addition, the glass-free lens covers and the operational controls are absolutely leak- and gap-free. The lenses and operational controls consist of non-diffusive and chemically-resistant materials. This means that the functional capability and impermeability of systems is ensured even after several years, and bacterial carry-overs are prevented. Wheels of cheese that are packaged in foils are reliably detected by these sensors.

Standard sensors are quickly pushed to their limits in packaging applications in the food industry and in systems for transporting food baskets. Because of the openings in bas-kets for fruit, vegetables or baked goods, standard sensors constantly generate unusable signal sequences. It is precisely here, however, that a clear switching signal would have obvious benefits for automation. The RK 46C VarOS sensor solves this problem. Unlike normal sensors that detect selectively, it detects objects over a band area of 60 mm.

In the light-band, the object sensor can detect objects with various sizes and shapes as well as surfaces with openings. In the past, multiple sensors and considerable installation work were necessary for this purpose. Adjustable sensitivity levels and automatic sensitivity readjustment (ALC) support high system availability in the event of soiling and changing environmental conditions – even stretch-wrapped or shrink-wrapped objects are reliably detected.

Cubic sensors, so as those already described, are not always an advantage. There are applications in which cylindrical series ("cylindrical sensors") prove to be the better choice and, above all, simplify mounting considerably. Furthermore, the cylindrical 328 series, for example, offers greater mechanical strength than a standard product made of high-quality plastic thanks to its metal sleeve. 

Available as operating principles here are throughbeam photoelectric sensors and retro-reflective photoelectric sensor – as well as light scanners with sensitivity adjustment by means of a teach button. With their different operating ranges of up to 15 m (throughbeam photoelectric sensors), 6 m (retro-reflective photoelectric sensors) and 1 m (light scanners) and due to their compact design, they are ideally suited for a wide range of applications where object detection is important, be it in materials handling or packaging technology.

Device model FT328, in particular, is predestined as a label sensor. Much more expensive solutions with cameras are frequently used that also require complicated adjustments by the operator. The FT 328 label sensor reliably detects paper and plastic labels on glossy containers, and adjustments are performed easily and quickly using a teach button.

Before labels are attached, they are supplied by dispensers – at a very high pace with conveyor speeds of up to 120 m/min with high positioning accuracies. This requires highly precise switching processes. Forked sensors with extremely short reaction times control, for example, the position of self-adhesive labels directly on the dispensing edge.

Regardless of the shape and material and regardless of whether matt or glossy surfaces – forked sensors enable precise and fast detection – even at high web speeds – and the reliable detection of a wide range of material combinations and surfaces.

Leuze electronic offers a variety of designs and operating principles – from ultrasonics to light. The IGSU 14D is an ultrasonic forked sensor suitable for universal use as its large mouth width allows it to also be used for booklets and fan-fold flyers. One special advantage is its easyTeach function by means of which it is immediately available for reading labels - practically at the touch of a button. The properties of the labels play no role, because "clear on clear", i.e., transparent labels on transparent base material, is reliably detected. The IGSU 14D SD device model, on the other hand, is a so-called splice sensor with integrated paper tear monitoring – predestined for the detection of splices on paper or plastic webs.

With the help of contrast scanners, marks and cut marks are precisely positioned in wrap-around labeling machines. Arbitrary colors and, in some cases, very small print marks, place high demands on the used contrast scanners. With a response time of 33 microseconds, interchangeable lenses and other features, such as its 2-button teach function, the KRT 21 scores especially strong here and can reliably detect any contrast marks. The simple adjustment to the mark and the background facilitates uncomplicated commissioning, even in blister and thermoforming machines as well as in foil packaging machines.

One aspect that comes into play in filling systems, among other places, is, in addition to the reading of codes and inspection of labels, combined process monitoring. "Inspection systems in beverage filling systems are often highly customized solutions that are implemented between the individual process steps," explains Bernhard Voigt, managing director of Voigt Technology e.K.

The range of inspection systems in the field of beverage filling systems ranges from the inspection of empties and full case checks to bottle contour detections, fill-level monitoring, the inspection of caps for incorrect mounting, and label inspections to rejection systems.One of his projects was the equipping of filling lines in the traditional sparkling wine winery Herres, located in Trier, with inspection systems for detecting and checking printed 2D Data Matrix codes on sparkling wine boxes. The LSIS 462i smart camera device versions from Leuze electronic are true all-rounders and combine functions for quality control (measurement function) and code reading in one device.

At Herres, great importance is placed on the advantage for maintenance: "For code reading, we use the LSIS 462i all-round version because we already successfully use smart cameras of the LSIS 400i series in other applications, such as for image processing with-in the scope of cap monitoring. This allows us to limit spare-parts inventory to one fully equipped device model that we can use everywhere if necessary."

Particularly with inspection machines, sensors from Leuze electronic can fully exploit their advantage in speed and precision, as high repeatability and switching frequency are essential for reliable function for the triggering of the camera systems. With laser and red-light optics, one can find exactly the right sensor for every trigger. Special sensors with explosion protection certifications enable use in explosive atmospheres, e.g., for the packaging of hair sprays or alcoholic beverages.

In addition to application-optimised sensors, the manufacturer from Owen also offers complete solutions, such as the LSC 200 3D measurement station. This is a complete system consisting of sensors and an evaluation unit. Depending on the task, a wide range of sensors can be connected and evaluated. When measuring dimensions, for example, the width measurement can be performed with a light section sensor or a scanner. The length measurement can also optionally be performed with incremental transmitters.

LSC 200 stations with CML 700i light curtains contain an integrated web visualisation system. With this, the measurement values can be directly displayed and adjustment values set by means of a standard browser. Furthermore, the user data can be made available to the user via a defined interface (e.g., PROFIBUS, TCP/IP).

As can be seen, there are a number of solutions for very specific tasks in highly automated packaging systems. Thanks to their decades of experience, the "sensor people" at Leuze electronic in Owen are familiar with many possibilities for designing packaging and logistic processes more reliably, more efficiently and more safely. In this regard, the sensor manufacturer's product line shows very few gaps. In many cases, it is simply a matter of receiving sound advice. The Service department at Leuze electronic can provide help here.