In recent years, a metal detector has become a vital inspection machine to eliminate contaminated products from the production line to deliver safe products to consumers. Anritsu Infivis Co., Ltd. has been providing metal detector solutions for a wide range of food production lines in over 40 years since 1981 by meeting the changing demands of manufacturers. In Japan, the mandatory implementation of the HCCP program for the food industry will be enforced starting from this year (2020). This program requires not only food manufacturers but also retailers and distributors to follow the HACCP program—this affects several hundred thousand of people in the industry.

In other countries, including USA and China, all the equipment used in food production is required to have a simple structure for easy maintenance under the food safety act of each country. This trend indicates that a metal detector with high detection sensitivity as well as its thorough usability and hygienic design are required in challenging production lines.

This article introduces the latest trends regarding the safety and features of metal detectors with an example of our latest metal detector, the M6-h Series.

Multiple Detection Modes

A metal detector monitors the change in magnetic fields in order to detect metal contaminants in food products. Inspected products vary from dry to wet products, with various packaging material such as aluminium-evaporated film. Some of the latest metal detectors are capable of generating several frequencies of magnetic fields. Moreover, metal detectors with dual-frequency systems are increasingly used in the production line to detect both ferrous and non-ferrous metals at high sensitivity.

Until recently, our metal detectors only generated two types of magnetic fields simultaneously among four types of frequency bands, from A to D. There are seven types of effective combinations (detection mode), which allows an operator to select the optimum mode for the product to be inspected. With our latest model, the M6-h Series Metal Detector, an operator can choose from nine types of detection modes, enhancing superior detection sensitivity according to the product characteristics.

Algorithms To Reduce Product Effect

Similar to metal detectors, X-ray inspection systems are also used for identifying contaminants in the production line. X-ray systems perform image processing using algorithm that is suitable for the product’s characteristics. For example, cereal appears on the x-ray transmission image in uneven colour with a granular pattern so that the algorithm is used to control the product effect of cereal evenly in order to enhance detection sensitivity. If the same approach is applied to a metal detector, detection sensitivity of metal contaminants can be improved.

The latest model, the M6-h, is equipped with multiple algorithms. These algorithms reduce effect of product to detect contaminants easily. The metal detector will automatically choose the algorithms for the product so that the operator does not need to worry about choosing algorithms.

Algorithms That Find Specific Contaminants

Equipped with algorithms specialised for specific contaminants, the M6-h enhances detection sensitivity for identifying specific foreign objects. For example, linear contaminants can be seen on the production line when part of a slicer is coming off during manufacturing.

Our latest metal detectors employ the most suitable algorithm for extracting a signal obtained from a particular contaminant like those linear metals. It cannot make the size of detectable test pieces smaller—however, it is effective for verification of detection sensitivity when using the actual metal contaminants. Moreover, it is useful when re-inspection is required for products in the same lot when there is a product suspected to contain foreign objects.

Operation Guidance Function

The operation guidance function ensures that the operation check is conducted before and after using a metal detector. An operation check is carried out at the start and the end of production to verify that a metal detector works properly by using test pieces and sample PASS products. Under HACCP regulations, manufacturers are required to keep a recording of sensitivity checks and rejection confirmation with the date, time, and the name of the operator who performed it.

With our metal detectors, if an operator does not follow the verification process according to the guidance, the production cannot be started or completed properly. The history of each operation check can be recorded electronically (Fig. 6), eliminating the use of paper and pen that can cause a possible contamination on the production line.

Hygienic Design

In the food production factory, taking tools on a factory floor should be minimised for the purpose of preventing any possible contamination on the production line. Anritsu’s M6-h metal detector with a hygienic design allows quick and easy cleaning without tools. A carrying conveyor and a motor can be separated from the main unit by removing a catch clip (Fig. 2: Images 1 to 4). The carrying conveyor can be simply removed by folding a part of the conveyor (Fig. 2: Images 5 to 8). The tool-free removal of parts of the system eliminates the operator’s burden associated with cleaning.

The Future Of Safe Production

A metal detector is an essential system for the inspection of food products on the production line. Among distributors and food suppliers, carrying out the inspection using a metal detector is taken into account as the business deal in many cases. With the recent advancement of social networking services, contamination of foreign objects in food products can be a big topic on the SNS that can easily harm the brand’s reputation.

For the safety of food products and to safeguard the brand of the manufacturers, it is necessary for metal detector to offer superior detection performance in the future. We will strive to put more effort into developing advanced technology to meet those demands from processors.

Contributed by Takuya Narita from Anritsu.

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