Quality Inspection is an indispensable element of responsible manufacturing and packaging of food products. It is imperative to maintain high quality and ensure consumer safety with food and health products. Moreover, global food safety initiative (GFSI) requirements are not limited to the food or drugs/devices themselves, but also include their packaging. Therefore, any contamination of food and health products and their associated packaging with impurities of any type could have serious consequences for a company. Manufacturers have adopted different systems for contaminant inspection to prevent such problems.

X-Ray Systems Supersede Conventional Metal Detectors

Metal detectors are most useful for the detection of magnetic and nonmagnetic metals. However, they have limitations in the inspection of aluminum-coated packing materials, whereby only metals of larger sizes are detectable in this type of packaging. Contaminations with glass, ceramics, stones, and similar materials also constitute a serious problem. X-Ray inspection systems have become more common for such applications in the food and pharmaceutical industries in the past 10 to 15 years. They offer an advantage over conventional metal detectors because X-Rays can detect not only a wide variety of foreign dense materials but also can-do with a much higher detection resolution.

X-Ray systems develop their images by measuring the amount of X-Ray energy absorbed by a product at the linear detector. The detector, which typically has individual diodes of 0.4 mm or 0.8 mm, are aligned side-by-side and scanned at a very high rate. The information received at each diode is called a pixel, and these pixels have a gray scale value that is proportional to the density of the product. When the pixels are placed beside each other, you get a line scan. By moving the product across the detector with a belt and then positioning the scan lines next to each other, you construct the X-Ray image.

X-Ray technology has been able to evolve over the years to ensure higher levels of product safety because of its versatility. For instance, older X-Ray systems were substantially limited by the capabilities of the Windows XP operating software used. Contemporary X-Ray systems still maintain a user-friendly Windows environment as an operating platform, but separate the image processing into a non-Windows-based system, such as Linux. This allows for a faster and more robust processing. In addition, Linux is the leading operating system on big servers and is used on the fastest supercomputers; therefore, it lends itself to be ideally suited for the enhanced processing required for package integrity inspection.

Versatile X-Ray Inspection System Allows For Extended Applications

The leading X-Ray technologies have the capability to detect contaminants while simultaneously enhancing packaged product quality. It is not practical for all packages to be manually inspected by operators for verification of the integrity of the product inside closed boxes or ready-to-sell products. X-Ray technology offers the ability to ensure product integrity or completeness by using high-resolution detectors, combined with the fast processing power of an efficient operating system. Therefore, the enhanced capability of the modern X-Ray systems allows for the performance of tasks which would not have been possible just a few years back, especially as speed of packaging lines increase with higher degrees of automation. More efficient operating systems provide the basis for smarter image analysis. For example, these illustrations of a cracked pizza crust (Figure 1a) and a broken cookie (Figure 1b) demonstrate automatic detection of out of specification products inside packaging.

Figure 1a

Figure 1b

In addition, a contemporary X-Ray system can also count the number of discrete objects in a package or even use the image data for checkweighing purposes. It has long been established that wood is not detectable as a foreign material with X-Ray technology. However, Figure 2 demonstrates that X-Ray can detect and automatically reject ice cream novelties with not only missing sticks, but even when the stick is too short.

Figure 2

Another application of a modern X-Ray inspection system is the detection of plastics. It is well­known that not all plastics are detectable as foreign materials by X-Ray. However, many medical devices and products are packaged or dosed from plastic containers. Figure 3 shows a prefilled syringe, inside a carton, with correct length and another one, which has been compressed. X-Ray can measure the length of the syringe, account for any rotation or skew to improve accuracy, and then reject syringes of incorrect lengths. Since the incorrect length implies a deviation from the right dosage, the X-Ray system assures product integrity, which cannot be done by any other system.

Figure 3

Many products can be presented chaotically or combined so they are assembled completely at random within a package. Best detection performance with an X-Ray is achieved when a product specific setup is chosen. Although different products can be inspected using a single setting, the setting is often a trade-off, which results in poorer performance on one product or a higher degree of false rejects. An X-Ray system, which utilizes new software techniques can actually automatically recognize chaotic or multiple different products as they are presented to an X-Ray. Figure 4 shows chicken thighs and drumsticks that are typically packaged at random on a production line. The software highlights the recognized products on the screen.

Figure 4

With more robotic automation coming to production lines, X-Ray can often automatically recognize different products better than a vision system. This capability can be used to alert the robotic systems which products are coming to them. Up to four production lines can be simultaneously inspected due to newer X-Ray – source architecture of “bottom­up shoot”. This new trend in configuration of the X-Ray source, which is placed under the conveyor, provides a full width inspection of the production line as compared to older architecture machines that are “top-down” shoot where the top corners are blind.

Future Perspectives

The newest generation of X-Ray systems offers not only advantages compared to conventional metal detectors but also to the older X-Ray technologies. In addition to detecting contaminants, it allows for product quality inspection by detecting product integrity, completeness, and positioning within closed shapes and packaging. Moreover, it allows for a quality parallel detection of two different products, incorrectly placed, or overlapping products. The modern X-Ray technology has been designed to operate safely for the inspected products and also for the operators by the production lines. Importantly, X-Ray detection has established itself as the standard for inspecting product purity, quality and integrity. It has become more affordable over the years due to the improvement of technology and software. Adoption of the latest long-life X-Ray tube, combined with proprietary real-time software running on an industrial PCs using flash memory, ensures faster image processing, reliability and ease of use. The benefits of X-Ray inspection systems are well recognized by the experts in the field. The advantages of the next generation X-Ray systems over the metal detectors and the older X-Ray technologies are now a significant part of a payback justification and the main reason for installing them across the industries.