A colour sorter is an optical machine that inspects every grain or seed with cameras. It blows off-colour pieces out of the stream with short jets of compressed air. Indian manufacturers build colour sorters, and imported machines are also sold and serviced in India.
"Sortex" is a brand name. In India the trade often uses it as a general word for any optical colour sorter.
How a colour sorter works
Product flows down inclined chutes, or along a belt, in a thin single layer. Cameras view each piece as it falls. Software compares what it sees with the accept settings for that product.
When a piece falls outside the settings, a fast ejector valve fires a jet of air and pushes it into the reject channel. Good product carries on to the accept outlet.
Machines differ in camera type, image resolution, and whether they also use infrared or shape recognition. They also differ in the number of channels and ejectors. More channels mean more capacity. Capacity depends on the product and on how much of it must be rejected.
What it is used for
- Rice and pulses, to remove discoloured, chalky or damaged grains.
- Seed spices such as cumin and fennel, to remove stones, stems and foreign seeds that earlier cleaning missed.
- Nuts and sesame, to remove shrivelled, mouldy or discoloured kernels.
- Dehydrated vegetable flakes, to remove dark or burnt pieces.
How to compare machines
Brochure accuracy figures are hard to compare. A trial with your own product is far more useful. Feed the machine a sample with a known level of defects, then measure two things.
- Accept purity: how many defects remain in the accepted product.
- Reject ratio: how much good product is lost in the reject stream.
- Also ask whether you can get spare ejector valves, software updates and service engineers in your country.
- Confirm the compressed air requirement, because a sorter needs clean, dry, oil-free air in large volume.
Running a sorter well
A sorter works best on product that is already cleaned and graded, as described in seed and spice cleaning machines. Dust on the camera windows reduces accuracy, so the area needs good dust control. Operators need training to set and save recipes for each product. Ambient heat and unstable power can also cause faults, so ask the maker about operating limits and whether a voltage stabiliser is advised. Many lines pass the reject stream through a second pass to recover good product.
A sorter is a precise electronic machine, so plan for software support over its life. Ask how updates are delivered and whether the maker can connect remotely to help with settings. Build the sorter trial into your acceptance tests, as explained in FAT and SAT.
Next step
We shortlist sorter makers, arrange trials with your product and check the results before you commit. To discuss your line, book a free sourcing review.