Technical profile: color sorting technology

by Teresa Acklin
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Contributed by suppliers, technical profiles feature new technology, products, specific applications or proprietary concepts. This material was provided by Buhler A.G., Uzwil, Switzerland.

   This year, Sortex celebrates 50 years of activity. During this time, the company has been at the forefront of color sorting technology. The original concept of color sorting emerged in 1947 with the first owners, Gunsons Seeds, and was born out of a necessity to enhance the quality of their agricultural seed producing operations.

   Sortex now employs 145 people in Great Britain and another 36 in the United States and around the world. The company today offers a wide range of sorting equipment, with many variations possible in addition.

   Commodities that the equipment can handle range from the many varieties of rice and grain, which are processed at rates of several tonnes per hour, through to high-value crops such as coffee and nuts. In recent years, Sortex has been actively involved with addressing the sorting problems of the vegetable processing industry.

   Since the early days, Sortex has steadily grown in size and stature. It was quickly realized that the sorting process could be easily adapted to the needs of the food processing industry, culminating in the development of the first production model, the G1 in late 1948, for Batchelors Peas (Unilever).

   The company was renamed Sortex Ltd. in 1962 and has changed ownership twice, most recently being incorporated as an active member of the Buhler Group in early 1994. Sortex also acquired the facilities of Scan-Core in the U.S. state of California in 1988, whose name was standardized as Sortex Inc. in 1994.

      Breathtaking pace of development.

   The sorting technology over the last 50 years has moved forward at an incredible pace. The first G1 machines used a relatively simple arrangement of photoelectric cells linked to electrostatic charging of defective product with 5,000 volts to deflect it away from the main product stream.

   The operation of many current machines is based on the principle of scanning the product using CCD camera arrays in any of one, two or rarely three wavelengths of light (mono, bi or trichromatic). These can include infrared or true color. The defects are then deflected and removed from the product stream by firing at them with pulses of compressed air.

   Other common methods of removal are by suction, which is used with wet products such as cubed tomatoes, and by flipper bars for larger items such as potatoes.

   The latest generation of sorters (Sortex Niagara) is now capable of sorting trichromatically as standard and also significantly by shape and size recognition. For example, the Niagara will be able to detect stalks that are the same shade of green as the beans. New software called “Smart-eject” will enable ejectors not just to fire at the defective spot on the product (possibly not ejecting it cleanly), but actually firing at the whole profile of that product item to ensure clean removal.

      Challenging future.

   Bruno Kilshaw, managing director, explains: “Sortex now has many challenges ahead with increased competition in the marketplace and tighter consumer and customer requirements. However, there are also many other opportunities to be pursued as advances in technology enable modern vision systems to resolve problems that hitherto were impossible. Today, customers expect the highest standards, and the new generation of Sortex machines is set to handle the toughest demands. The vegetable food sector also offers many opportunities, with many processors seeking to add value to their products and taking advantage of the growth in the prepared foods sector.”