Inspection technologies keep an eye on things: many kinds of inspection systems are available to packagers who want to kick their quality control up a notch - Inspection Systems

Food & Drug Packaging, Sept, 2003 by Pan Demetrakakes

When it comes to quality control, there's often more than one way to look at things.

Packagers who want to inspect packages on-line have several options in terms of basic technology: vision systems, X-rays, profiling systems, compression and more. For some functions, only one technology is realistic, but for others, two or more are feasible. To make the proper choice in such cases, you must weigh numerous factors, including line speed, packaging type and degree of accuracy required.

Here is a look at some of the major on-line inspection technologies, and the type of applications they're best suited to:

Vision systems

Camera-based inspection is one of the most versatile on-line quality control technologies. Cameras can look at several packaging parameters at once, including missing or askew closures and labels, missing objects, fill levels, seal integrity and more. One of the advantages of vision systems is scalability, the potential for adding parameters after the initial installation.

"Once you capture an image with your camera, you can look at that image and do many different things with it," says Kris Bierbaum, packaging industry account manager for Cognex Corp.

Vision systems depend more on computing power than most other inspection technologies. It's no surprise, then, that they have evolved along with computers generally. Early units were connected to a remote processing unit; today's models are more likely to have processors embedded in the camera.

"Camera is almost a misnomer because they're really small computers," says Richard Daigle, media relations manager for DVT Corp. "All of hard work is done within this little box."

From a practical standpoint, this means vision systems come in many degrees of sophistication. The lower-end ones are more like sensors, capable only of determining relatively simple conditions like presence/absence. More expensive systems use more complex algorithms that can detect subtler deviations from a packaging standard. These can be used for more demanding tasks like optical character verification/recognition. Vision systems can also perform extremely specialized functions, such as the Perceptics SealSafe Product on Flange system that detects contaminants on the flanges of zipper seals on pouches filled on a horizontal form-fill-seal line.

Lower-end systems have the advantages of simplicity and low cost. "There are a lot of features you can add to [a vision system] that tend to complicate things, that typically are not used by a majority of users," says Dan Holste, vision products manager with Banner Engineering.

On the other hand, applications sometimes take an unexpected turn, making users wish they had invested in a more expensive system. Bierbaum cites the example of a pie company, worried about peanut allergies, that installed a bar code sensor to ensure that peanut-butter pies would not get into the wrong cartons. But a carton redesign that rotated the bar code 90 degrees left the system useless. Rather than reconfigure or upgrade the scanner, the company asked Cognex for a vision system that can recognize codes and characters in any format, at any distance and in difficult lighting conditions.

Easy adaptability is one of the biggest advantages of higher-end vision systems, says Mark Sipple, vision product marketing manager for Omron Electronics. "That's probably one of the biggest advantages, because you can make a changeover on a vision system by simply adjusting its programming," Sipple says."

Metal detection

Electromagnetic metal detection is perhaps the most prevalent form of on-line packaging inspection. Metal detectors can be found at various points throughout all kinds of consumer-goods packaging facilities.

Metal detectors can be useful for monitoring incoming as well as outgoing goods, says George Louli, director of marketing for Safeline Metal Detection,

"A little bit of contaminant [in ingredients] can spread throughout a lot of product," Louli says. "Some people would argue, well, if you got the metal detection at the end, then who cares. But if you get a little piece, by the time it's mixed up and blended, it can get into a sizable amount of product, which you would be rejecting and having to dispose of, versus just catching maybe a half-pound of flour."

The biggest advantages of metal detection over competing systems are price and robustness. Metal detectors are less expensive than systems that interpret images, such as vision or X-ray, because they don't depend on computer processing technology. They also tend to be sturdy, solid units that stand up well to wash-downs and other in-plant stresses.

X-ray detection (visual)

X-ray units are among the most versatile on-line inspection systems. They can find a range of problems, including missing elements in primary or secondary packages, deformations in product, bad fill levels and more.

One of the biggest advantages of X-ray inspection is its ability to find non-metal contaminants, such as cherry pits or plastic film shards, that electromagnetic metal detection can't. X-ray systems also can handle metal packaging.