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Feature Articles

Visible to X-ray, Food Packaging Uses Entire Vision Spectrum to Meet its Needs

by Winn Hardin, Contributing Editor - AIA

CognexLike many other manufacturing industries, the food packaging industry is adopting more vision technology each year with an eye to increasing productivity. But while productivity is the end goal for any company in the private sector, the food packaging industry faces unique challenges to its margins.

These drivers come from two main sources: government institutions, through agencies such as the US Food & Drug Association (FDA), Department of Agriculture (USDA) and the international food standard organization Codex Alimentarius Commission and their respective regulations such as the US' Hazard Analysis and Critical Control Point (HACCP, pronounced Hassip); and the emerging class of megastores that negotiate national contracts for food distribution.

Both drivers are pushing liability away from the distributors, grocery stores, restaurants and large institutions and towards suppliers. The reason, according to the US government, is a simple: numbers. According to the US Department of Health and Human Services' Center for Food Safety & Applied Nutrition (CFSAN), '…the size of the food industry and the diversity of products and processes have grown tremendously - in the amount of domestic food manufactured and the number and kinds of food imported. At the same time, FDA and state and local agencies have the same limited level of resources to ensure food safety.'

Vision's expanding role in food packaging
'Vision is finding its way into projects that wouldn't have been considered 5 or 10 years ago,' explained Inex Vision Systems (Clearwater, FL) president, Glen Long. 'A desire for greater security in food and tight quality controls from warehouse clubs and other major customers are pushing food manufacturers to head off the defects before they are shipped to reduce return costs.'

Stringent controls from large customers have their origins in end user expectations, according to Doug Peariso, quality assurance manager for baby food manufacturer Gerber Products Company (Freemont, MI). For this reason, Peariso added that innovative inspection and quality assurance techniques are critical to a profitable business plan in today's market, and a big part of that is investing in technology. He points out that the FDA has issued 8 recalls for foreign material issues in the food industry since January 2001, while the USDA has issued 5 during the same time frame. 'Large processors usually don't have inexpensive recalls!' he said recently during the 2002 Food Safety Summit.

On the other side of the coin, best practice manufacturing process that include detailed inspection systems help limit manufacturer's liability. 'Good detection strategies can defeat false claims/consumer tampering,' Peariso said. Following procedures included in HACCP not only limit defective product and returns, the procedures also give suppliers the ability to defend themselves against fraudulent claims if they arise.

Based on procedures originally developed by NASA for astronaut's food preparation, HACCP incorporates seven basic principles: analyze hazards and identify measures to control those hazards; identify critical control points in food production; establish preventive measures with critical limits, typically centered around critical control points; establish procedures to monitor the critical control points, of which vision inspection systems are one avenue; establish corrective actions for when critical limits are exceeded; establish procedures to verify that the systems and monitors are working properly; and provide record keeping to document the entire process. Using a HACCP approach can greatly reduce both the introduction of foreign material through standard production and equipment maintenance, and the detection of special case material where only inspection and detection can solve the unexpected problem.

A label is just a label, or is it?
Vision systems in food packaging applications fall into two basic categories: label and package verification, and seal and contaminate analysis. Cintex of America (Kenosha, WI) provides vision systems that operate in both the visible and x-ray spectrums for food packaging applications, in addition to non-imaging metal detection systems and PLC 'check weigh' systems for weighing, sizing etc. 'Optical vision has the most play in food packaging,' explained Cintex's manager of sales and marketing, Dan Izzard. 'We have color PC based vision systems that look at the package, the bar code, read the expiration or sell-by date and determine if they are correct.'

Like its competitors in the food packaging industry, most of Cintex's components are off the shelf vision systems. However, the 5 percent that is proprietary - in the form of diode lighting arrays, specific frame grabber selection, software selection, x-ray source and detectors - are what tend to separate a successful food packaging inspection system from a 'general purpose' headache for food suppliers. Even the largest vision suppliers, such as Cognex Corp. (Natick, MA), who are sometimes described as general purpose vision suppliers, understand that nothing substitutes for experience when it comes to food packaging. 'About eight months ago, we released two new software packages, CapInspect and LabelInspect, because we saw that different companies were solving the same problems over and over again,' said industry marketing manager for food, Mark Helman. 'Vision is not a commodity, it takes specific knowledge and we're trying to inject as much industry specific knowledge into our software as we can.'

When it comes to x-ray inspection systems in food packaging, experience becomes even more crucial because the technology is not as widely used as vision systems that use the visible spectrum. 'The trick is to apply the technology properly and have the right expectations. Understanding the customer's contaminate size, weight specification, reliability of detection, and the desired false reject rate are all critical to a successful installation. It's easy to beat the specifications in the laboratory, but when you get outside the lab, you have to adjust inspection settings to compensate for natural variances in production,' commented Heimann Systems, Product Inspection Division (Alcoa, TN) managing director, Michael Ahern.

Heimann Systems uses the following table to determine whether x-ray systems will work for a given application based on identified contaminate sizes and desired false reject rates. Making the customer understand the systems capabilities help to ensure that all parties are satisfied.    


Other general guidelines associated with x-ray inspection include the size of the contaminate and the type of the contaminate in relationship to the object being inspected. X-ray works well on all metals, glass shards (even inside glass bottles), stones, some plastics and calcified bones.  The detection capability of contaminates is a direct relationship of the density of the product.  'You are looking for density and thickness of the contaminate relative to the product.  As an example, in a bowl of water 1 inch deep, we can find a 1-mm metal contaminate very easily. But if the water goes to 4 inches deep, the metal contaminate has to be 2 mm. Is that a limitation? Yes. For instance, most plastics are about the same density as water and because of that, x-rays can have problems with detecting plastics,' Ahern explained.

In addition to escalating customer expectations that foods be hot, ready and 100% contaminate free, Ahern points to an increase in the use of foil packaging as a driver for x-ray inspection systems during the packaging stage of food preparation. 'If companies move to foil packaging, they have to do x-ray because simple metal detection won't work. And there is a prevailing philosophy that the best quality system is to inspect the final package so there's no danger of a contaminate getting inside the package after that point in the process,' Ahern said.

Vision inspection offers winning combination
Additional 'check weigh' functionality, such as measuring size, portions, weight, etc., is also driving x-ray deployment. 'X-ray works on density measurements, and if you know the volume, then you can determine weight. We can even independently weigh different zones within a single package, such as cheese and crackers,' Ahern said.

According to a quick survey of vision system suppliers, a major driver behind the adoption of vision systems - both visible and x-ray - is the shrinking costs of deployment and operation. X-ray systems that used to go for $150,000 now sell for $70,000. Visible inspection systems can go as low as $4000, according to Inex's Long, but use of a experienced, full-service integrator will bring that cost of installation up to $25,000. 'But these systems are also networkable,' Long explained. 'With a single control point you can inspect multiple lines and that's a critical issue today. That's a lot of statistical gathering going on at the plant, and operators need to be able to analyze efficiency across different shifts, and with various operators. These systems allow the plant manager to make process changes or improvements on the fly,' Long added. 'In the past, the defect often wasn't found until they were shipped.'

As plants expand their contract manufacturing practices to include more products from different suppliers, and regulations continue to grow to manage this diverse product line, food packaging plants will turn more and more to vision inspection systems to help manage this growing complexity. 

Cintex of America
6919 51st Street
Kenosha, WI 53144

Heimann Systems Corp.
Product Inspection Division
3143 Regal Drive
Alcoa, TN 37701
Tel.: ++1 (865) 379-1670
Fax: ++1 (865) 379-1677

Inex Vision Systems
13075 US 19 North
Clearwater, FL 33764
Phone: +1 727 535-5502
Fax:     +1 727 532-8513

Cognex Corporation
One Vision Drive
Natick, MA 01760-2059
Directions to Cognex
Phone: (508) 650-3000
Fax: Company-wide: (508) 650-3333










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