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A GUIDE TO GLASS X-RAY INSPECTION FOR FOOD AND BEVERAGE 

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Advantages and Challenges of Glass for Food and Beverage Applications

No other packaging material has all the advantages of glass: unrivaled clarity; wide varieties; reusable, cost-effective, environmentally-friendly. According to a report by The Atlantic, “Glass has changed the world like no other substance….without glass, the world would be unrecognizable”.   In the E.U. alone, a total of 20.9 million tonnes of glass was used for food and beverage packaging (a 2,9% increase from the year before).

All this to say: glass use is growing. And it will likely continue to grow as society becomes sick of the recycling challenges and environmental impact of plastic. According to a survey of over 4,000 consumers conducted by research group EcoFocus Worldwide, 37% of consumers said they were extremely or very concerned about the health of safety of plastic use in food and beverage packaging.  

When it comes to manufacturers, there are two main reasons that glass is favored:

-the consumer assumption that things in glass are better products
-the perception from consumers that glass is inert – that is why you find baby food in glass  

While glass has a host of consumer benefits, it also poses some real challenges in container manufacturing and food and beverage operations: defects. During manufacturing, glass containers can incur a host of defects that are serious food safety risks – including material cracks, chips, loose glass inside the container, wall inclusions and more esoteric defects like bird swings. Dangerous glass shards can be accidentally introduced to containers during operations.

Because of this risk, every glass container should be inspected.

Not inspecting, or insufficient inspection can result in contaminated or defective products, which can lead to recalls. Recalls are expensive, time-consuming, and damage brand trust between company and customer. But they can be avoided with glass x-ray inspection.

Originally, glass inspection was performed by the human eye; and in some cases, still is.

There are, however, severe limitations to the efficiency of glass inspection on a manual basis. Inspecting glass “the old fashioned way” is slow, expensive, and always runs the risk of human error.

Wayne’s World conveyor belt scene

You may remember this scene from the cult classic film, Wayne’s World, when they performed quality assurance for glass beer bottles. The limitations of human inspection become quite apparent. It’s a lot less funny when it’s happening to a real product.

This is where x-ray technology bridges the gap between human limitations and scale production realities.

What Glass Container X-Ray Inspection Entails

Many people are surprised that it is possible to reliably detect glass fragments within a glass container – people assume that because the fragments are the same density as the container, they cannot reliably be detected. On the contrary: it is the added density of glass fragments within the container that allows them to be detected (this added density is simply due to the additional layers of glass created within the image).

In fact, glass in glass x-ray inspection systems are capable of reliably detecting: glass shards, stones, glass container defects, (e.g., bird swings), metal contaminants. 

 However, not all glass x-ray inspection machines have the same capabilities.

Challenges of Glass Inspection

-Depending on the physical design and software, an x-ray machine may face limitations in its ability to detect imperfections. Compared to other forms of food and beverage x-ray inspection, “glass container inspection” has a unique set of challenges:

-Detecting small contaminants in glass containers that are the same density of the container (e.g., detecting a glass shard in a glass bottle) requires significantly more inspection sensitivity than other applications

-Glass shards are by definition asymmetric objects – one dimension of the shard is often very small. Reliably detecting these types of contaminants requires more sophisticated multi-beam imaging systems.

-“Punts” or “push ups” are typical in glass containers, which can obstruct x-ray imaging.

-Contaminants also tend to rest in the “push-up”, the space between the punt and the container exterior wall, which can make them more difficult to find.

-Thicker walls on glass bottles can also require high levels of x-ray power, risking “image wash-out” of contaminants during an inspection.

-Speed:  Glass lines can operate as fast as 1300 containers per minute and hence inspection and rejection equipment must be extremely fast.

Overcoming Glass Inspection Challenges

Developing Strong Image Resolution

Perhaps the most critical element of glass container inspection is to take extremely high contrast x-ray images that clearly show the defects of interest. Manufacturers use a variety of technical approaches to maximize image quality; including very high contrast x-ray sources and very short distances between the x-ray source and detector. The results of these efforts are very easy to see in an actual x-ray image – pieces of foreign glass material are clear.

Multiple Beam X-Ray Inspection for Glass

As previously mentioned, multiple beam inspection systems are critical for proper detection of asymmetric glass particles.  Peco InspX uses two multi-beam architectures for glass inspection.

Shield Trio Architecture

Cutting-edge x-ray machines such as the ScanTrac Trio by Peco InspX provide an ingenious solution to all of the challenges presented in glass container inspection.

As stated above, single beam x-ray machines are limited in their capability to detect contaminants and defects. With a three-beam design, the Trio is able to overcome the challenges presented by glass inspection. As depicted in the illustration, the three beams can detect contaminants that would normally be obstructed by the punt. 

What is invisible for one beam is easily visible to another, eliminating blind spots.

In addition to detecting defects, the Trio can also inspect precise fill levels of containers; inspect for cap presence; and eliminate product spacing issues.

Shield Glissando Architecture

The Shield Glissando is Peco-InspX’s highest performance glass in glass inspection platform. The Glissando leverages a single metal ceramic x-ray tube with two high sensitivity detectors.

This design provides a multiple geometry inspection approach with a single x-ray source.0.8mm resolution detectors offer the best combination of speed and ability to detect lower density types of glass contaminants.

Best Practices For Glass Container X-Ray Inspection

Empty Glass Bottle Inspection

Before filling containers, it’s important to make sure the empty glass bottles are free of defects or contaminants. EBI’s or empty bottle inspectors are vision-based systems that are designed to inspect glass containers before they are filled. EBI’s are designed to detect things like cracks, and contaminants that would be undetectable by x-ray inspection.

Benefits of Traceability

One of the inherent benefits of using x-ray inspection technology is traceability. As part of the inspection process, an image of a container is generated and stored. If a contaminant is reported, the x-ray image can be reviewed to determine if the contaminant was present at the time of inspection. This process ensures that whoever performed the inspection will not be held responsible for the introduction of a contaminant during a time after the container left their jurisdiction.

Mold to Mold Variations in Glass Inspection Performance

Glass bottles are created with molds; but variations in molds – small flaws or defects, at times nearly invisible – can impact inspection performance. Inspection refers to individual physical measurement systems that specialize in finding different defects; mold inspections require highly specialized data. This is another area where x-ray inspection for glass shines: it can catch the variations in molds and determine defects before the glass bottle is even made.  

Sometimes, flaws or contaminants can create hairline fractures, compromising the glass. Even the smallest fracture must be identified during the molding process.

Challenge Test with Correct Density Test Pieces

Glass bottles inspection requires “challenge tests” to determine their durability and stability. Challenge test pieces require specific densities depending on the glass variation…but if these pieces lack the correct density, the challenge test is compromised, and the results are flawed.

Choose An Inspection Vendor Who Is An Expert In Glass Inspection

When deciding to invest in glass inspection x-ray technology, you should think of it more as a partnership, instead of a one-time purchase. You will want to partner with an experienced company that has extensive knowledge of x-ray glass inspection. Should any questions or complications arise, your partner will be able to quickly and confidently provide a solution.

Data Analysis

The company you partner with should offer detailed inspection data analysis. Being able to analyze data provides the opportunity to optimize your manufacturing processes and ensure you are getting the most out of your x-ray machine software and hardware. Proper analysis of inspection data will result in greater manufacturing efficiency, customer happiness and profit margins.

Watch this video from Peco-Inspx to see the “Why” behind x-ray inspection.

Glass container inspection comes with a unique set of challenges, so it is critical to invest in a machine that is able to overcome them. Besides offering the highest probabilities for detecting contaminants and flaws, the ScanTrac Trio goes above and beyond by providing other precise inspection criteria such as lid presence and fill level. The Shield Glissando takes glass inspection performance even further by offering the best combination of speed and detection ability.

If you’re interested in a demo of how Peco-Inspx can help your glass inspection process, watch our full product demo video and fill out the form.

 

For more information, visit HBM Plastics Technologies

 

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