February 2020

56 n SENSORS February 2020 www.drivesncontrols.com Beer bottles come under laser scrutiny A fter they have been emptied, beer bottles that have reached customers from filling lines or breweries, usually take the same route back. The recyclable glass bottles can be refilled, typically 40 to 50 times. The bottles arrive back at breweries in their thousands to be checked, washed and refilled. To ensure that further machine processes – such as the removal of caps and labels, as well as washing and refilling – proceed smoothly, it is necessary to inspect the crates as they arrive. Completeness of the bottle is a crucial factor, but ensuring that it is the correct type of bottle in the right crate is also important. The wide variety of bottles in circulation presents a challenge for bottlers and breweries. Often, the glass is trimmed with a brewery’s logo, or the bottles are specially shaped for a particular manufacturer. It is estimated that more than a third of the bottles delivered to breweries arrive in the wrong crates. The crates are often inspected manually, a process which is exhausting, subject to error, and costly in terms of human inspection hours. As the crates move along a conveyor, they demand a lot of concentration from the inspectors. If they become tired, the wrong bottles can slip through, or some crates might be incomplete. A more efficient inspection method, which is claimed to be absolutely reliable, is to use non-contact laser scanners. The Slovak company Tipteh has developed an inspection system that relies on laser line triangulation sensors for fast, automated inspection, and is already being used to inspect received beer bottle crates. The scanners are located above the crates as they move along a conveyor belt at speeds of up to 850mm/s. There are five scanners, each one measuring a single row of bottles in the crates. Compared to systems that use conventional image-processing technologies, the laser scanners monitor not only the presence of a bottle, but also its height. The bottle heights are used to determine whether the correct type of bottle is in the crate. The height must not deviate by more than 3mm from a target value for each type of bottle. A PLC receives the result of the evaluation as an "OK" or "not OK" signal, allowing any faulty crates to be removed from the production line. The measured results can also be shown on a display built into the controller. For its inline inspection system, Tipteh is using five scanControl 2900-50 laser scanners from Micro-Epsilon, which have built-in controllers. The sensors are based on a laser triangulation principle that provides 2D profile detection. They emit a laser beam that is widened to form a laser line that hits the bottles. The laser light is reflected and projected onto a sensitive receiving matrix in the sensor. As well as distance information (z-axis), the controller can also calculate positions along the laser line (x-axis). These measured values are then output in a 2D co-ordinate system fixed with respect to the sensor. If the scanned objects or the sensor are moving, it is possible to obtain 3D measurement values. The sensors can perform up to 2,000 profiles per second and are suitable for both static and dynamic processes. The challenges of the bottle-inspection task lie mainly in the varying reflective properties of the bottles. These can differ due to different glass colours (usually green and brown hues). In addition, the bottles may arrive with or without caps and this is recognised by the scanner using pre-stored algorithms. As they are being transported along the conveyor, the bottles vibrate and shake. The laser scanners overcome this by capturing all of the points across the line simultaneously. They can be positioned a long way away from the bottles and can detect 1,280 measuring points per profile. The measured values can be evaluated on the production line. Raw data is fed using the GigE Vision protocol into image-processing software for evaluation. The data can be stored for subsequent statistical analysis and process optimisation. n A Slovakian company has developed a technology that uses laser scanners to measure the presence and height of beer bottles in moving crates. It can check whether all of the bottles are present and that the crates contain the right type of bottle. Tipteh’s technology can check that returned crates of beer bottles contain the correct bottles as they move along a conveyor The five laser scanners each check one row of bottles in a crate