That's cracked it: Trio of sorters improves production efficiency at walnut factory

This line format is gentler on the product, and more efficient than sending the nuts through one machine three times, the company says. It is also a way to tackle false reject rates.

The Cayman BioPrint and Optyx sorters, which are used in the cascading line, are on display at Pack Expo in Chicago this week.

Separating walnuts from shells​

The Poindexter Nut Company’s production facility in Fowler, California, installed a cascading line made up of three digital sorters from Key Technology.

The sorting machines are used after the cracker to separate walnut kernels from shells, membranes, and foreign material. They also distinguish the different colourings of the nuts. This can be done at a rate of up to 10,000lbs (4.5 metric tons) an hour.

Mike Poindexter, CEO, Poindexter Nut Company, told FoodProductionDaily.com:  “It’s extremely important to separate shells from kernels - If a customer accidently finds a shell, it can break a tooth.​

“But​ false rejects cause yield loss, which has a direct impact on the bottom line.”​

“This cascading line of three sorters is much more efficient than running three passes on one sorter. It’s also much gentler. What hurts walnuts isn’t flying through the air, it’s accelerating and decelerating. Dropping into a bin or out of bin is what damages walnuts.”​

The line-up​

In the line, two Cayman BioPrint hyperspectral sorters are followed by an Optyx camera/laser sorter.

The Cayman BioPrint removes shells, using hyperspectral imaging (instead of cameras and lasers). Hyperspectral imaging uses intelligent software and algorithms to recognize the biological characteristics of objects.

This BioPrint technology gives the machine 99.5% sorting efficiency, with low false reject rates, claims Key Technology.

While the first Cayman removes the majority of shells, the second Cayman runs on a ‘more aggressive setting’ to clear out any remaining shells. The sorters are able to deal with spikes in high defect loads,  which makes them suitable for use after the cracker to separate shells from kernels.

By using two sorters, the line produces a much clearer product stream to maximise efficiency at the next stage, the company says.

Detecting nut colour​

The third machine, the Optyx, removes foreign materials such as plastic, glass, stones and sticks. It also clears out any remaining shells and membranes. The Optyx uses cameras which pick up on the colour of nuts or other objects. This means it can sort the nuts into three streams: good product, colour rejects, and unwanted shells.

The Optyx can be equipped with top and bottom mounted cameras and lasers, on a two-way or three-way sorting platform.

Marco Azzaretti, advanced inspection systems product manager, Key Technology, said: “Attempting to remove all defects with one sorter results in a high percentage of false rejects and also combines many different types of rejects together in one stream. ​

"Rejects from the Cayman BioPrint sorters need to be re-cracked to separate embedded meats from the shells.​

“The Optyx camera/laser sorter then removes colour defects and shape sorts to keep each type of reject separate, in its own classification, which reduces the sorting that needs to be done on the rejected material.”​

Key Technology designs and manufacturers process automation systems including digital sorters, conveyors and processing equipment.