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High speed inspection for contaminants and defects

20 April 2020

Changing its X-ray inspection equipment has allowed a fruit bar producer to ensure it is able to efficiently and accurately detect foreign bodies as well as identify a host of product defects. 

Viba Sweets manufactures a wide variety of fruit bars comprising over 60 recipes in various pack sizes with fill weights ranging from 8g to 50g. Its high-capacity line can reach a maximum output of more than 500 fruit bars per minute. Because it is a natural product, the dried fruit mixture between the wafers can sometimes contain impurities such as tiny stones or fragments of glass – so before end-of-line packing, X-ray inspection technology is used to check the healthy snacks for foreign bodies.

When the legacy X-ray inspection system used by the company was found to no  longer meet the manufacturer’s standards, it set out to find a solution that would. Francisco Taberner process and project engineer at Viba Sweets, takes up the story: “Because the fruit bars are very light, their positions and the gaps between them on the conveyor belt would change as a result of them coming into contact with the curtains at the infeed to the X-ray system. That meant that there was a risk of contaminated products not being reliably rejected.” There was also a need for more information to help determine the types of foreign bodies and to pinpoint their locations in the product to identify the causes.

After exhaustive tests of machines from several suppliers, Viba Sweets selected the IX-EN X-ray inspection system from Ishida. This machine is now working at high speed in two-shift and three-shift operations at the factory. Defective packs are being reliably rejected without causing delays to the process, as the stainless-steel curtains move so smoothly that touching them has no effect on the fruit bars. Reject confirmation software provides an extra layer of safety, stopping the system immediately if product deemed contaminated is not detected by a sensor in the reject container within a defined time frame.

Good detection rates
Since installation of the new system, Viba Sweets has reported good detection rates for stone, glass, dense plastic and metal. For example, stones and glass fragments measuring 1mm and above, for example, can now be reliably detected even at high inspection speeds. The system also employs a weight-checking function as an indicator of additional defects that would previously have gone unnoticed. 

Deformed and broken fruit bars can be identified, while any packs that have accidentally been filled twice can be taken off the line. A data log collects all the important information and the reports are proving to be useful in helping identify causes and eliminating recurring sources of contamination.

The IX-EN x-ray inspection system is said to be well suited to use with fruit bars because it was developed specifically for checking thin, lightweight and comparatively homogeneous products. It searches for foreign bodies by measuring the density of the product. The X-ray beam passes through the fruit bars onto a line sensor. Depending on the strength of the returning X-ray beam, a grey-scale image is produced. Any particles denser than the product itself appear as dark spots on the image. “The touchscreen on the machine immediately provides information on the nature of the foreign bodies and exactly where in the product they are hiding,” said Taberner.

The inspection system also meets the need for high accuracy. “The software is much more powerful than our previous machine, as well as being better than the other machines that we tested,” continued Taberner. 

The technology behind the IX-EN X-ray inspection system is based on software featuring an intelligent genetic algorithm. By analysing image data over a number of generations, the machine achieves a high level of accuracy because similar contaminants can be found again and again in food production, so it is possible to create an increasingly accurate comparison log with each inspection procedure. The system can be calibrated quickly and easily by passing an X-ray beam through a test object two to three times.

According to Taberner, the production team found the machine to be easy to use. After an automatic set-up process, the system is ready for use within 90 seconds, and fine adjustments can be made during production. Up to 200 programmable pre-sets allow product changeovers at the touch of a button.

“New recipes can be loaded in just a few minutes, and the easy access to all mechanical parts makes cleaning much quicker,” concluded Taberner. 

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