For metal detectors, physical size and orientation, especially of conductive products, can impact the inspection, Todd Grube, product manager, inspection systems, Heat and Control pointed out. It can also help determine the type of technology.

“For metal detection, manufacturers must determine whether their products require a single-frequency unit, multi-frequency or multi-spectrum technology exclusive to our CEIA metal detectors.”

To properly match the system with the product size and type, the key is working with a variety of frequencies.

“Often, the solution is to change the frequency of operation to minimize the effect,” said Steve Mason, sales manager at Fortress Technology.

But sometimes, choosing one frequency over another becomes a tradeoff.

“The downside of doing this is that it can impact the ability to find different metals,” he cautioned. “By dropping the frequency, the ability to find ferrous metals is enhanced but limits performance when it comes to finding non-ferrous metals because the lower end of the frequency is more responsive to magnetic effects of the contamination. By the same token, if the frequency is higher, the reverse happens; the ferrous detection capabilities are limited, but non-ferrous detection is enhanced.”

Today’s metal detectors solve this problem by operating on multiple frequencies at the same time. Mettler Toledo’s MSF metal detectors use a combination of high and low frequencies simultaneously, using two stages: frequency and phase.

“This cancels the input from combinations of high and low frequencies,” said Camilo Sanchez, product inspection product manager, metal detection, Mettler Toledo. “The result is effective removal of the product signal, allowing for much smaller contaminants to be detected.”

Vision technology can be integrated with metal detection for enhanced inspection. While these systems have typically focused on either the height difference or color variations, EyePro System spent several years developing its Multi-Eye technology to detect defects on the surface of a product.

“Our systems can inspect the quality of the products and identify defects often not detectible by other technologies,” said Erica Vannini, sales and customer service, EyePro System. It uses a combination of spectroscopy and imaging technology to acquire an image of the product at various wavelengths to detect the foreign body. “Think about a piece of white plastic on a mozzarella cheese pizza.”

This article is an excerpt from the July 2020 issue of Baking & Snack. To read the entire feature on inspection systems, click here.