Colour Sorting Machines

Colour sorting machines, as the name suggests, enable the sorting of individual items on a production line by colour. Most colour sorting machines nowadays use high-resolution optical sensors to identify items, and either a pneumatic or mechanical ejection device to expel unwanted items from the main line.

Colour sorting machines are most commonly used in the sorting of agricultural grain and rice, as well as in the processing of food products, such as coffee, nuts and oil crops. The optical sorter separates any stones, mouse droppings and discoloured, toxic or otherwise unacceptable items. Where a nut or seed, for example, has already been dehusked, the colour sorter will detect any remaining husk and separate the offending item from the rest for disposal or alternative use.



Since their first use three decades or so ago, the sophistication of colour sorting machines has developed significantly, in line with growing technological innovations. Technology has enabled ever more accurate and efficient colour sorting on production lines across a wide range of industries, saving time, labour and money.

As well as food items, one of the leading markets for colour sorter machine manufacturers is the diamond industry. Colour sorting machines are indispensable in this industry, facilitating the process of determining the purity of individual diamonds. Transparency is the key factor for determining the purity and, therefore, value of a diamond, which a colour sorter can do far more accurately than x-ray fluorescence or other methods of purity determination.

Colour sorting machines are also useful in the detection of impurities in minerals, stone, sand and ore, particularly when combined with x-ray sorting and optical colour sorters.

Types of Colour Sorting Machines

Chute Colour Sorter

Common in the food industry, chute colour sorting machinery is well-suited to production lines where high capacity runs are the norm. Equally, the design of a chute sorter means that optical sensors mounted on each side of the chute can be used simultaneously to detect imperfections on both sides of an individual product. For example, it may be the case that a nut is processed after dehulling that has some remaining hull on just one side. One downside of chute colour sorters is that individual items can be broken or damaged on passage through the chute, which can have a negative impact on wastage. It’s therefore important to determine whether this will be an issue for your particular product run.

Belt Colour Sorter

A belt-type colour sorter operates on a conveyor belt, with items being sorted by colour/suitability siphoned into different silos as they pass by the sensor. There is less risk of breakage with belt colour sorters as the product stays relatively static as it moves smoothly along the belt, preventing damage from bouncing, collision or friction.

Optical Sorting

Optical sorting uses cameras and/or lasers to automatically sort products. Along with colour sorting, optical sorters can also recognise size, shape, structure, and even chemical composition. It is an extremely efficient inspection method, completely non-destructive and with a 100% inspection rate. Parameters for sorting are programmed manually, making it simple to adjust parameters to suit different production runs. Optical sorting easily removes defective products and foreign bodies from the line, and can simultaneously or separately sort products into different grades, colours, etc.


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Common Terminology

  • Optical sorter
  • Digital sorter
  • Electronic colour sorter
  • Pneumatic ejection device
  • CCD optical sorter
  • X-ray fluorescence
  • Sensor-based sorting
  • Near infrared spectrometry
  • Chute colour sorter
  • Belt colour sorter
  • Rice colour sorting machine
  • Ejector valve
  • Colour optics
  • Elevator belt
  • Hopper
  • Food sorting machine