How do machines pick / reject tomatoes (and other items) so fast?
You probably have already come across the video below, a mesmerizing sample of how a machine automatically picks and rejects ripe and unripe tomatoes in a matter of milliseconds. In slow motion, this task becomes a real treat. But how can these devices make decisions so quickly and accurately? Jim Frost, the product manager for Tomra, the company that makes these steel selectors, responds.
“We have been selling these machines for 25 years. This selector, in particular (that of tomatoes), is like the 'mother of all selectors'. It is very basic and is often used in the field, ”says Frost. Tomra offers several models: Blizzard, which sortes frozen fruits and vegetables in free fall from pulses recorded by an LED camera; Cerberus, which classifies tobacco, detects the presence of metal and removes fragments; Felix, which removes foreign material and large "defects" in pounds and pounds of carrot and string beans; among others.
Scheme illustrating the operation of Tomra's Ixus Bulk with X-ray and imaging software that can remove metal, stone, glass, dense plastic and other food impurities
According to the expert, approximately 60% of processed foods today are separated by this procedure: a line of optical sensors crosses the conveyor belt and a row of "rejects" positioned like teeth on a comb expels unwanted items. “We use finger-like 'bouncers' for bigger products and air ones for smaller things.”
Check out a video of grape cleaning demonstration from Tomra rival Europress:
Durability is the big challenge
Although the whole process seems very complex, Frost says that machines make decisions very simply. The rejection of a nonstandard stone, clod, or fruit is made from unanswered "yes" or "no" answers - and this has been refined over the years.
In high season, up to 800 tons of vegetables are processed per hour
“Each of the 'fingers' works with a 30 or 40 millisecond window. They have to move, reject the item, and then return to their starting position as quickly as possible so as not to touch anything else, ”explains Frost. So the major challenge for engineering in this process is to build structures that can withstand repetitive stress for a long time.
In California's ripe tomato season, for example, they are harvested over a 12-week period, with sorters running up to 24 hours a day, processing up to 800 tons of vegetables per hour. At this time, farmers cannot afford to stop, as ripe fruit must be preserved or canned in one day. In fact, he himself gives a hint that few people knew - if it is really true: “Canned goods have a bad name, but they are one of the few foods that have as few additives as possible. It's just salt, tomato juice and tomatoes. Only that".
Now, about people's fascination with selector video - true viral on social networks - he says most don't know how technologies like this have become commonplace. “Sometimes we get to clients we've dealt with for years, and when they realize what's going on, they say, 'Oh my God, that's unbelievable!' And I say 'we have been doing this for 20 years; where were you? '