Weighing Prepared Foods: 4 Reasons X-ray Inspection is the Best Solution

Food & Beverage
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Prevent customer complaints and ensure compliance with average or net package weight regulations by choosing the right x-ray inspection system for weighing prepared foods.

There is a common misperception that conventional checkweighers are always more accurate and a better choice than x-ray systems. This is simply untrue. Using an x-ray inspection system, which ensures the correct amount of mass and thereby weight via x-ray absorption, has numerous advantages over a conventional checkweigher which uses gravitational pull to measure weight.

In the U.S. alone, ready meals have developed into a $26 billion market over the past five years. As consumer demand for convenience foods rises, the worldwide market is predicted to increase more than 4% by 2018. Now, more than ever, it is important to understand the benefits x-ray inspection affords convenient food manufacturers as a weighing solution.

No errors due to package and component weight variability

Unlike conventional checkweighers, food x-ray inspection systems can look inside final sealed ready meals and differentiate the contents from the packaging. Common examples of packaging which may have high variability include glass containers, multi-component packaging, composite material containers, and applications where the packaging materials are heavier than the package contents.

Not only can x-ray inspection systems determine the weight of the entire product, it can simultaneously check that all components are present, intact, contaminant free, and are placed in the correct position with each component’s weight checked and verified.

Vibrations and air currents are no match for x-ray machines

Keeping designs simple and deploying technologies that minimize performance risks are important in order to deliver a consistent accurate weight needed by most users. Two areas of major concern are vibrations and air currents. Each of these can have an extremely negative affect on the weigh conveyor of a conventional checkweigher. Yet, there is absolutely no impact on an x-ray system when it performs the checkweighing function.

Vibrations can come from inside the checkweigher due to misaligned drive motors, worn bearings, or poor product transfers to name a few. Near the machine, vibrations can come from adjacent conveyors, forklift traffic in nearby isle ways, or other product handling devices such as case packers and rotary fillers. All of this can negatively influence a conventional checkweighers’ performance.

It’s also difficult to isolate and eliminate air currents, both updrafts and downdrafts. Air handlers turning on and off, ceiling fans, as well as the opening and closing of doors which cause air movement can create instability in the weigh conveyor performance of a conventional checkweigher.

Beyond these influence factors, there are others which can lead to poor conventional checkweigher performance, including changes in temperature, package transfers on and off the weigh conveyor, timing and spacing, and throughput restrictions. These issues can be avoided with x-ray weighing as x-ray systems are not dependent on a weigh conveyor for results.

High-performance x-ray inspection machines use dynamic calibration and are not affected by conveyor vibration or air movement, as they are not dependent on the physical movement of a weigh cell for a measurement result. They simply require an x-ray image to be taken as each ready meal passes through the machine. This can make them ideal to use on a crowded production line, as they can be installed closer to surrounding machinery with no effect on performance and no need for additional precautionary measures to be taken.

Outstanding weighing accuracy on high speed production lines

Conventional checkweighers require sufficient time to get each individual ready meal onto the weigh conveyor to take a series of sample readings which is then averaged into a weight. This is known as “weigh time”. The weigh conveyor must be longer than the longest package, and depending on the manufacturer, this requires a distance range of anywhere from an additional 20% of a package to a full package length. In addition, because the weigh conveyor is based on the longest package to be run, the speeds and corresponding production rates for shorter packages must be adjusted to accommodate this restriction. Package spacing or pitch issues increase handling complexity and may require additional acceleration or deceleration.

X-ray systems do not require weigh time. The ready meal is scanned, the image is processed, and the mass or weight is derived. Only a minimal package separation is required in order to distinguish one package from another. Furthermore, there is no dependency on the longest package, so shorter package speeds and spacing does not need to be adjusted to deliver accurate results.

Accuracy specifications quoted by gravimetric checkweighers are frequently unrealistic in terms of their routine attainability on a production line. Problems quickly arise as the pack-per-minute rate increases and the checkweighers become less accurate and more restrictive. X-ray inspection systems used for weighing have a clear advantage as their accuracy does not deteriorate with product speed and repetition rate. X-ray machines perform at very high throughput rates. In many cases, they exceed 1,000 packages per minute, delivering both unparalleled contaminant detection while also performing the weighing function.

X-ray Inspection = Checkweigh + Contaminant Detection + Component Count + Selective Area Weight

X-ray systems can tolerate ready meals touching, and they’re capable of weighing selected areas within a ready meal. Conventional checkweighers can’t make those claims.

Selective area weighing is achieved by evaluating each independent area of the ready meal. This is beneficial for process monitoring and diagnosis of in-process variations that cannot be identified by conventional checkweighers. Additionally, inspection checks verify each item within the ready meal is in its correct position and separated from the other ready meal components. This ensures the product is as attractive inside the box as it is on the outside. While conventional checkweighers may flag a problem, x-ray systems with weighing functionality show what the problem actually is. For example, not enough mashed potatoes in a ready meal. By helping to identify where the process is dysfunctional, x-ray systems enable manufacturers to adjust processes upstream, helping to reduce customer complaints and minimize product waste.

X-ray imaging software provides images of each individual product that can be retrieved for Quality Assurance investigations. Rest assured you will have full traceability with reporting capabilities to improve production processes and operational efficiencies. Add to this the x-ray systems’ ability to assure food safety and quality assurance by detecting physical contaminants and product defects, and it’s easy to see how an x-ray system undoubtedly provides ready meal manufacturers with a system of unparalleled value.

By Christy Draus, Marketing Manager at Eagle Product Inspection

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