NON-CONTACT MEASUREMENT & INSPECTION FEATURE
maximise throughput can be self-defeating if the detector can’t tell when one pack ends and the next starts. Sensors can miss the millimetre gaps between the units required for the light beam of a conventional optical sensor to make contact with its reflector on the opposite side of the conveyor. With the new SICK DeltaPac
No matter for reflection?
When identifying products in automated processes, some materials, colours and shapes can be a challenge. Phil Dyas, industrial sensors product manager for SICK UK, looks into new technologies capable of sensing hard-to-detect objects
S
ensors which identify individual products and packs for critical
automated processes such as counting, picking or quality monitoring, can find some highly-reflective, matt or transparent materials more or less ‘invisible’. The same is true for some product shapes or packs with radiused, folded or faceted corners. The resulting mis-detection could result
in high reject rates which, at best, can lead to regular stoppages and, at worst, result in hefty customer fines and returns through mislabelled, wrongly packed or miscounted goods. Particularly challenging, for example, are
some electronics products such as the solar cells used in photovoltaic panels specifically-designed to absorb light, or high-gloss glass instrument display panels. In addition, while matt black provides a glamorous and luxurious feel for confectionery and cosmetics packaging, it absorbs light readily. At the other extreme, highly-reflective chrome and mirror finishes can confuse a conventional sensor by scattering the sensor’s light beams and causing false signals. Transparent packaging – such as shrink
wrap, clear plastic trays or bottles –may be completely missed by the detector; and unusual angled or rounded shapes can cause stoppages and downtime through poor sensor detection rates. Now, however, solutions are
emerging that offer the optimum price/benefit performance for specific applications while being flexible enough to cope with frequent product changeovers on a production line. Being able to simply detect any
product or pack reliably and affordably is now possible with new smarter sensing technologies.
Transparent packaging – such as shrink wrap, clear plastic trays or bottles – may be completely missed by the detector
On man-made surfaces, even the most matt black finishes are around
4-5% reflectance. To the average sensor this is like staring into a black hole
DETECTION In nature, the deadest matt blacks on animals and plants can have a light reflectance of 1% or less. Tropical butterflies such as the Parides species from South East Asia, for example, use matt black on their wings as a way of hiding from their enemies in their jungle habitats. On man-made surfaces, even the most matt black finishes are around 4-5% reflectance. To the average sensor this is like staring into a black hole, even under bright lighting. With SICK’s new W2S family of high power sub-miniature photoelectric positioning sensors, however, reflectance levels down to 1% are easy to pick up, so difficulties with black invisibility are no longer a problem. The four models in the W2S sensors
range are contained in a miniature, rugged, IP67-rated housing incorporating the latest high-power PinPoint LED. This emits a high visibility light spot at sensing ranges up to 3m via the high sensitivity multi-pixel array detector. With a tightly-focussed spot
and sophisticated background suppression software, the range of models ensures high reliability and consistency whether detecting jet black, brightly-coloured, matt, transparent or highly-reflective objects.
CROWD CONTROL Crowding FMCG products on a conveyor to
/ INSTRUMENTATION
multitask photoelectric sensor, productivity is boosted by making gap-free, high-speed product conveying achievable without sacrificing accuracy or risking frequent pile-ups, downstream quality and stoppages. This can also detect changes in shape
at line speeds of up to 3m/s and 200,000 units an hour. Rated to IP67, DeltaPac uses light beams from four PinPoint2.0 LEDs to track edges moved across them by the conveying line, including object radii from 1-20mm within the 30-40mm range.
A CLEAR SOLUTION Transparency can provide a window for attractively-coloured contents in trays, bottles or jars. But, sensors can struggle to pick up a clearly-defined signal, and heat shrinking films or protective wraps can create further multi-reflective clutter. The new SICK TranspaTect
photoelectric sensor delivers consistent detection of transparent containers. A key development was removing the requirement for a traditional reflector for the light beam, which can be inconvenient and difficult to accommodate. Instead, the sensor uses a matt surface of a convenient machine component as a reference surface. TranspaTect’s new Auto Adapt feature
automatically compensates in sensitivity for sudden contamination of the lens or reference sheet and then re-establishes the original threshold levels when they are cleaned up. Based on a high-performance PinPoint
LED, the TranspaTect detecting range for transparent objects is 0-400mm and the background reference range is 150- 700mm. The compact sensor is IP66/67 rated and TranspaTect has ECOLAB certification of its resistance to aggressive cleaning regimes, disinfectants and chemicals for a long, reliable working life.
ENHANCED ABILITIES With these enhanced performance abilities, the new SICK sensor families could inject new life into conveying line and automation efficiency, and free the constraints on the designers’ imaginations.
SICK T: 01727 831121
www.sick.com/uk Enter 665
INSTRUMENTATION | JUNE 2014 25
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