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Automation Technologies 5/2014

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Automation Technologies 5/2014

Machine Vision Variable

Machine Vision Variable object sensors detect irregular objects Dieter Eßlinger The detection of objects with changing shapes and dimensions, optical detection with selective light beams becomes a challenge. Retro-reflective photoelectric sensors with light-band detect everything safely and reliably and carry out this task. This technology has numerous advantages in many applications, especially in packaging systems and intralogistics. Author: Dieter Eßlinger, product marketing manager, Leuze electronic GmbH + Co. KG, Owen, Germany If objects have inclined or curved shapes or surfaces with cutouts and holes, irregular edges or variable heights, optical detection with selective light beams becomes a challenge. In practice, such cases are varied and occur in nearly all industries. While different object heights and container formats can be handled relatively easily as long they are known, it is a much more difficult task with heterogeneous objects. Typical examples from practical experience include damaged pallets – where boards may be missing – or stacked products with overhanging or protruding elements. To all of the non-cubic objects that are transported on the conveyor systems used in intralogistics or in packaging systems, whether machine components or shrink-wrapped pallets with variable external shape, presence monitoring and positioning applications with standard sensors are difficult and complex. This also applies for objects with interrupted surfaces, especially when they are of varying size and

Machine Vision next page with irregularly distributed openings. Light scanners and photoelectric sensors, which are otherwise the sensors of choice, must then be arranged in a complex manner and often used in combination in order to detect the front edges of the objects that are to be identified. The innovative light-band of the RK 46C VarOS sensors brings this to an end. Sensors with light-band - in principle a retro-reflective photoelectric sensor The main advantage of the sensors with light-band is, compared to alternative, standard sensor concepts with combined transmitter and receiver modules, they considera-bly reduce material and installation 01 Reliable detection of pallets of varying sizes At first glance, the light-band sensors function in the same way as the familiar retro-reflective photoelectric sensors of the 46 series. This is due primarily to the same compact housing shape of the entire series – but also because no special reflectors are required; here, the 40 × 60 mm or 100 × 100 mm standard Whether nonuniform, non-cubic, irregular or variably changing object shapes – the variable object sensors detect everything costs. Instead of combinations of multiple individual photoelectric sensors, small light barriers or complex, multiple switching configurations, now a single light-band sensor suffices. With this, Leuze electronic demonstrates in concrete terms how Smarter Application Know-How can be advantageously implemented for the user in technology and in practice. The special feature of the VarOS is a specially developed Fresnel lens that, instead of discrete laser beams, generates a very homogeneous light-band (red light) with a con-siderable width of 45 to 60 mm. This makes possible the reliable detection of objects variably over the entire width of the light-band with just one sensor. The sensor reacts to all objects that appear within the light-band depending on the taught sensitivity (resolution). It doesn‘t matter where the light-band is broken by the object. Reliable detection of laminate panels of varying sizes reflectors can be used. Last but not least, the use of identical parts in the housing and electronics components brings considerable advantages with respect to production and, as a result, cost. Maximum performance under rough conditions The VarOS makes two easily teachable, preset sensitivity levels available to the user (one standard setting and one for increased sensitivity). Sensors can thereby be quickly and optimally adapted to object sizes and surface properties. The first sensitivity level, “standard setting”, is suitable for objects 12 mm and larger. It offers a maximum operating range with largest possible performance reserve in the event of soiling or vibrations. Typical areas of application include, e.g., pallet applications. In the second sensitivity level, objects 8 mm and larger are reliably detected. This setting is AUTOMATION TECHNOLOGIES 5/2014

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