Sorting Out NTRM

Source from:  Tobacco Journal International 07/15/2009

08 Jul 2009. Suppliers of sorting equipment for tobacco processing can breathe easy: there are no signs that demand for their technology is waning. TJI talked to two companies about their latest business opportunities and the advantages of laser- versus camera-based sorting systems. Belgian company Best and US-based Key Technology, both providers of sorting solutions, report that orders from Asia are up, with most demand coming from India, Indonesia, and the Middle East. China, of course, which is modernising its entire tobacco manufacturing industry, is also playing a big role, but the market is closely regulated. Investment activities in the US and South America, meanwhile, are lagging behind those in other regions. The demand for tobacco sorters is coming in particular from green leaf threshing (GLT) plants. For one, there are plenty of threshing plants in the world that still employ manual labour for sorting out non-tobacco related material (NTRM). "Many GLT processors still believe they can do the sorting manually," says Steven Van Geel, area sales manager at Best, "but those who have installed an optical system know that this is a more than worthwhile investment. No manual activity can match the effectiveness of optical systems." To put it bluntly, the human eye is simply not up to the task. Pickers have difficulty spotting small objects or material similar in colour to tobacco. And even the most efficient pickers tend to specialise in one sort of NTRM. So great care needs to be taken on where to place the pickers and how to organise each shift efficiently. By contrast, an optical system takes out NTRM with constant alertness, at a higher efficiency rate and at a speed of three to five metres per second. All optical sorting systems applied to the tobacco industry work with air ejector valves. These eject the NTRM effectively since the flight path of any object can be calculated accurately. Most importantly, a sorting system can handle volumes of up to ten tonnes per hour, per production line, where the equivalent manpower would easily be more than 100 pickers, so Van Geel. [b]Modular update[/b] For those processing plants which have optical sorters in place, there are good reasons for investing in an update, reports David Felts, sales manager specialised applications at Key Technology, a market leader in supplying sorting systems to the tobacco industry. "Especially plants in North America and Europe, which bought their systems in the early and mid 1990s, are upgrading their systems to newer sorting technologies," says Felts. Customers upgrade to Key's most advanced vision engine, called G6, which is a camera-based solution offered by Key since 2005. G6 is the internal vision engine that contains all electronics and thus the electro-optical foundation for all Key sorters. "You can compare it to the hardware and software that works together in a computer," says Felts. The system was designed by Key to incorporate the best of its previous technology, which was made up of five different vision system platforms after Key's acquisition of SRC Vision in July 2000. (These original systems were Optisort, by Key and SRC, Kromasort by SRC, Advanced Vision Processing by SRC, and Tegra operating system by Key). Felts explains the advantages of G6: "It is very stable, powerful software, easily upgradeable and the modular construction greatly helps fulfil the needs of our customers. The Tobacco Sorter II, for example, which runs on Kromasort, can be upgraded to the G6 vision engine. By replacing only the controller module, an upgrade to the newest technologies is far less costly than replacing the sorter." About 25 G6 updates have been carried out so far in tobacco processing by Key in all parts of the world. Best also offers a modular update with its laser-based bio-sorter. Biological sorting, i.e. sorting by biological content, is one of the most promising developments in sorting, says Van Geel. "Biological properties are the single most distinct difference between NTRM and tobacco. With the exception of some organics, you can differentiate between all types of NTRM and tobacco." This is a major breakthrough for an industry that is confronted with sorting probably the most challenging product. For one, the colours of NTRM and tobacco are so close that NTRM is often not identified as such by either cameras or laser-based "colour" sorters. Major difficulties also arise because even the good product varies enormously, i.e. there is no standard size or shape of tobacco leaf. This differs vastly from other branches that use sorting technology. In food processing, for example, peas, corn or raisins always come at around the same size. Hence, Best has developed a technology that increases the distinctiveness of the signature of any material, contributing to better tobacco sorting. The technology behind biological sorting is a screening with fluorescence, whereby a certain wavelength enters the product and is reflected in a different wavelength, creating a "day and night" difference. Best, which was operating in food processing before entering the tobacco market in 2003, reports that bio-sorting takes out non-biological matter, such as synthetics (plastic, rubber, polystyrene) or any other non-synthetic materials (wood, paper, feathers, cloth) far more effectively than the methods available so far. These other methods are colour sorting, which separates material by colour as well as by different intensities of a colour, and infrared sorting, which measures the penetration of light into the structure of the material. Since each method analyses specific properties of a material, Best installs all three sorting modules. "This increases the average efficiency rate to 90 per cent, compared to rates that are about 20 per cent lower when using colour and infrared sorting only," so Van Geel. Camera-based systems, too, achieve efficiency gains. Key's G6 system now includes cameras that provide 1,028 pixels - up from 840 pixels - and the cameras' scan rate has increased from 1,000 to up to 8,000 scans per second. Pixel sizes go down to 0.5 mm, allowing for a far higher resolution and thus better colour segmentation in a picture. "We can now segment into more colours. And the transition pixels, which define the border of an object, are eliminated more efficiently," says Felts. These transition pixels can take the colours of both NTRM and tobacco, so with fewer of these "in-between" pixels, a better fine-tuning of the sorter is possible. [b]Camera vs laser[/b] As efficiency rates of optical systems continue to improve, the technological upgrade of sorting systems is only a question of time. The difficulties lie in choosing between a camera- and a laser-based system. Best, which supplies camera-based sorting solutions to other industries, maintains that in tobacco processing, no camera can match the effectiveness of laser-based technology. The company sold nearly 20 of its laser sorters to the tobacco industry in 2008 (and nearly 140 when adding those sold for food applications) - a clear sign, they say, that costumers appreciate the benefits of laser technology. Yet the technology leading the market is clearly still based on cameras. Even the most advanced, high-tech camera system is cheaper than laser technology. In the longer run, however, the cost of laser technology might fall in line with that of cameras. Key Technology is not claiming that cost consideration is the most significant factor in favour of camera systems. Instead, argues Felts, "the main attractiveness of camera systems lies in its intuitive nature. Our RGB (red-green-blue) cameras cover the full spectrum width of light, so the machine "sees" things at their true colour. The true colour picture is then displayed on the active touch screen and the operator can look at actual pictures, which makes the operation of the sorting system at the interface a lot easier and more intuitive." There is yet another factor that is crucial when installing any sorting system: maintenance. This is one of the biggest issues in running any sorting system. However, choosing between a camera- and a laser-based system can be difficult because both representatives of the competing technologies claim that their technology requires the least maintenance. Looking ahead, Felts argues that, while the optical parts of camera-sorters could be improved further, the more important question would be whether the efficiency gains one achieves make the investment worthwhile. Key could, for example, offer laser-based technology, which it has in place in food-processing sorters. Even a technologically advanced camera-based solution for sorting via ultra-violet light exists. "However," says Felts, "at some point, it doesn't matter what kind of sorting technology you have, because you can only spot the NTRM that is actually visible. Tobacco can fold and thus hide smaller pieces of NTRM from view altogether. At Key, we got to the point where we think that more benefits can be achieved by developing improved mechanical processes - such as better spreading out the tobacco - or advanced software." So Key does not only focus on the vision system of its sorter, but approaches sorting in a "general, all-embracing way". The company is working on improving the way the product is transported to make it as open as possible and to distribute and stabilise it through the vision and ejection zone. "Just as important as vision definition and ejection accuracy is that the object to be targeted is removed in a plane separate from the visual plane," adds Felts. "Stability of the travel direction and speed of that object from the visual plane is critical to removing it, which is ensured by Key Technology's patented air-assisted transport belt." At Best, product handling is also approached in an integrated way. The company says that by cooperating with OEMS (original equipment manufacturers) worldwide, they can offer the most advanced and efficient solution with respect to the product handling, i.e. avoidance of degradation, and optimised product flow towards the sorter, i.e. uniform spreading. In addition to product feeding, Best employs another method to improve the spreading of tobacco. Their sorters operate with a free-falling product flow. Unlike "free-flight" operations, there is no difference in velocity and hence no difference in the flight path of NTRM and tobacco. "This results in an ideal mono-layer, meaning an even and natural spreading of NTRM and tobacco," so Van Geel. For further improvements in sorting tobacco, Best is adopting trends from the food industry and is currently working on a system that involves multiple sorters, each tackling a very specific issue. Enditem