Metal detection vs X-ray inspection: which is better?


Detecting foreign contaminants in your product before they leave your processing plant ensures your goods meet specs – your customers’ and yours. It’s an excellent way to protect your brand, but which will help you achieve your goal: metal detection or X-ray systems?



Metal detection and X-ray inspection have long been the first check food & beverage processors. But, as you’d expect, the technologies have changed – dramatically. These massive progressions in engineering and software mean it’s not instantly clear which will be best for your application.

For food & beverage applications, the system often needs to be able to pick up the smallest contaminants from thousands of products in challenging processing environments. So whichever system you chose has to meet some basic needs:

  • extremely sensitive
  • easy-to-use
  • fast
  • fully automatic
  • robust
  • reliable
  • cost effective

To help you make your decision on which to invest in to ensure the safety and quality of your products, consider these questions:


1. What contaminants do you want to detect?

Conventionally, metal detection systems have been used to detect metal (including aluminium and wires), while X-ray inspection detects all metals, as well as many other solid contaminants (think glass, stones and bones). However, today’s technology means advanced metal detection systems can also detect non-ferrous metals.


Typically, X-ray inspection systems can find smaller contaminants than metal detectors and can check a wider range of materials, including large packaged products, cases, cans and bottles. However, there are challenges for both systems. As a rule, metal detection systems find it difficult to ignore wet and salty products, as they are conductive. While X-ray inspection systems have limited success when it comes to dense products with lots of texture. That said, there are examples of advanced systems that can overcome both these issues.


2. What type is your packaging?

Many food & beverage brand owners have switched to metallised film or foil-based packaging to enhance their products’ appearance or shelf life. This instantly rules out metal detectors, because they can’t get past the packaging to see any contaminants inside. X-ray inspection systems however, can see right through into foil-based packaging to detect extremely small foreign objects. Make sure you take into account how you might change your packaging down the track, as this will determine the best investment for your inspection processes.


3. What’s your application’s speed?

Finding a system that will perform at the rapid speeds is often a main challenge, and this is where many X-ray systems come up short because their speed range may be limited due to the scanning rate. X-ray systems also need a continuous, known speed to build images, so they cannot be used in gravity-flow applications, unlike metal detection systems, which can be used almost anywhere in the process.


4. What’s the optimum detection point? 

It’s important to consider the stage in your processing line with the greatest of finding contaminants, and this will influence which technology you should use to gain the best performance. Metal detectors can be installed almost anywhere along the line, but their success largely depends on the size of the opening in the metal detector that the product passes through. So that means they tend to work best for products in small packages and bulk conveyed products. By contrast, X-ray systems have greater sensitivity with large products. In both cases, processors and packers can often derive the best value by placing the unit at the end of the line, examining finished (i.e. packaged) products.


5. What else can the technology do?

No matter the technology, it’s always worth thinking about how you can get the most value for your business. Here, look at what the systems can do as well as detecting contaminants. For example, X-ray inspection systems can see inside a container to detect missing products in a pack — something that’s not possible with a metal detector. X-ray systems can also inspect a product by measuring the shape, counting objects or using the density of the image to estimate weight. Each of these processes helps to ensure that only the highest quality products are leaving your factory doors.


6. What’s the total cost of ownership (TCO)?

Another aspect to consider — and again no matter the technology — is not just the upfront purchase cost, but the equipment’s total cost of ownership (or TCO) over its lifetime. TCO includes training, maintenance, repair, parts and so on. Generally, X-ray systems are more expensive up front than metal detection systems, while metal detectors last up to five times longer. If your application means examining small, dry products, then an X-ray system’s extra functions won’t add any value to your business, so go for a metal detector. But if you need to go beyond the basics, then an X-ray system could prove a worthy investment over the long term. (You may find these articles explaining TCO and how reducing TCO can help improve your bottom line interesting.)


7. The result

You’ll notice we haven’t said “A” is better than “B”, and that’s because one solution does not suit every application. There are so many different factors that affect performance, so the best way to choose your ideal inspection system is to look at your own exact application, product and industry needs. Contact the experts at iQVision for information about the different systems on offer and how they can be configured to meet your needs.



A foreign-object detection system’s performance is determined in three ways:

  1. Minimum contaminant size: This depends on the system design and technology as well as the “product effect”. This is the degree to which the food looks like a contaminant to the detection system.
  2. Detectable contaminant types: There are lots of contaminant types, including glass, rocks, bones, plastic, pieces of metal and so on. Often, the real challenge isn’t finding the contaminant, but ignoring the packaging, product and environment. False detections can quickly add up both in terms of time and costs.
  3. Probability of detection: What is the chance of the system missing a contaminant in real production, with real products running at real speeds? As a general rule, the larger the contaminant, the higher the probability of detection. However, you also need to build in a margin for error, with periodic audits and preventative maintenance.


You may find this blog on which inspection technologies can be used for ready meals interesting too.


Here’s some further reading: with a quick guide to 5 different types of inspection equipment processors can use and a best practice guide to inspection systems.


iQVision has years of experience customising applications from the simple to the complex. For more information or guidance on choosing the right vision solutions and technology for your application, please contact us via email or call 1300 IQVISION (1300 478 474).


iQVision also has a host of information in the resource library, including videos, case studies, whitepapers, brochures, FAQ’s and our blog. They’re all free to download. 

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