Ounces of savings, pounds of profit

Overweight means “out of shape” on production lines, too, but checkweighers can help you tone your lines.

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By Mike Pehanich, Plant Operations Editor

You’ve cut what seems like tons of fat from plant operations. But they’ve asked for more. Where to look?

One area to check is the production line itself. Incorporating the latest generation of checkweighers into your production lines can convert those ounces, grams and milligrams into pounds of newfound profit on the bottom line.

Checkweigher application spans a wide range of products, from snacks to cheese, powders to liquids. The equipment also can handle the whole gamut of packaging, from bags, cans, bottles, overwraps and trays to tubes, cartons and flexible packages, or even unwrapped product.

Precise measurement and distribution of ingredients as well as the final product can have big impact on your plant operations. That’s why checkweighers are carrying heavy responsibility on today’s production lines to deliver consistently accurate measurements that give both consumer and processor alike a fair shake.

“Checkweighers really do two things,” says Pat Helm, managing partner of The Manufacturing Systems Group Inc. and adjunct professor at the University of Cincinnati’s school of applied science. “First, they help meet the government’s minimum weight requirements. Second, they optimize adherence to weight goals, using feedback to the filling system to keep weights close to target so the processor isn’t giving away product.”

The checkweigher’s link with computerized information and control systems amplifies its worth, enabling real-time readings of package filling, documentation of entire runs and automatic line adjustments based on fill trending data.

“It ties into the SCADA system, your pyramid of controls," says Helm. “You can feed information directly into the QC lab. But if you misapply it, you’re done. It can shut the line down. So reliability must be high. You want a checkweigher’s efficiency in excess of 99.9 percent.”

The latest generation of checkweighers also integrates easily with other automated inspection devices. These integrated systems form centers for on-line, real-time quality control/quality assurance by monitoring package or carton closure, missing caps, bar code labels and the presence of metal or other contaminants.

The most immediate benefit a checkweigher provides is assurance of 100 percent compliance with fill standards. A checkweigher, by its very design and function, checks the weight of every product on the line. Since its first appearance in the processing plant, checkweighers have become critical quality assurance tools, ascertaining and sorting overfills and underfills and virtually guaranteeing satisfaction of net contents requirements.

But you’ll find profit potential behind the advancing popularity of today’s checkweighers. Fractions of ounces of waste and product giveaway add up quickly. Use the multiplier of a long production run, and the processor may soon be looking at tens or hundreds of thousands of dollars in savings over time.

A matter of measure

A checkweigher is a device that weighs items as they pass through test or production lines, and it classifies and sorts, delivers or rejects measured items according to the degree of accurate product measure. A checkweigher segregates product – usually packaged product – by weight.

Though units may vary with use and design, a typical checkweigher is comprised of an infeed section, scale, discharge area and typically a rejector or line divider. The advantage of an in-motion checkweigher is its ability to determine weights and component presence accurately at production speeds.

The value of a checkweigher to any given processor depends on need and function.

Fresh cheese processor Arthur Schuman Inc. added an Alpha PW12 checkweigher to its plant in Fairfield, N.J., several years ago. “It was a new line, a new application,” recalls Vincent Angiolillo, vice president of operations. “We wanted to improve profitability – and make sure that the customer gets what he’s paying for.”

Another advantage was the tracking data the checkweigher enabled the company to produce. “It helps keep our costs down,” says Angiolillo.

“They expect us to produce the correct quantity every time,” says Tom McCaffer, vice president of operations for Peacock Engineering, a contract food manufacturer with plants in Geneva and Itasca, Ill. The company co-packs for a number of food giants, including Kraft, Quaker Oats and Land O’ Lakes. It has incorporated Loma’s AS 1200 C checkweighers into its operations. In addition to running at line speeds up to 260 feet per minute with accuracy up to 0.5 grams, the unit’s memory can hold up to 100 separate product specifications and links with other plant devices – of tremendous benefit when packing multiple products for multiple food marketers.

While accuracy is the primary concern of a cheese processor running 60 to 120 packages per minute, speed may be just as important to big players such as Frito-Lay, whose line speeds may run several times that rate. The larger the production run, the higher the cost of waste and giveaway.

“The checkweigher market has been dominated by domestically made equipment,” says Gary Wilson, president of Loma International (www.loma.com), based in Carol Stream, Ill. “Historically, requirements in the U.S. market have tended toward hearty, robust, rugged equipment capable of running at relatively fast speeds for three shifts a day. The driving force in the Asian market, on the other hand, has been accuracy. They don’t run their equipment as fast in Asia, but customers there have demanded greater accuracy.”

An expanding mandate to squeeze greater profit from operations has put a higher premium on accuracy in the North American market in recent years. Today, processors simply can’t afford overfill.

“The North American market is changing now,” says Wilson. “Accuracy is becoming more important. Production needs to be more efficient. Giveaway is an issue because profit margins are an issue.”

“It is common for checkweighers to run at 200-300 packs per minute in the United States and even Europe,” agrees San Sin, who heads sales and marketing for Singapore-based Virtual Measurements. “In Asia, lines tend to run at slower speeds.”

His company has established a North American base in Santa Rosa, Calif. It views the American food industry’s growing demand for greater accuracy as an opportunity to serve. He points to high quality strain gauge load cells and the high processing speeds of the CPU for his equipment’s ability to achieve accurate weight readings at high speeds.

“The tolerances are tighter today,” says Kyle Thomas, marketing manager for Hi-Speed Checkweigher Co., Ithaca, N.Y. (www.hispeedcheckweigher.com). “Not only are companies concerned with compliance with net contents laws and giving the customers what they are paying for. They are also making sure they are not giving away too much.

“The more sensitive we can make our devices, the more we can diminish shrinkage, material loss,” he continues. “It’s a matter of increasing productivity. Checkweighers enable you not only to be a good steward of the consumer, but also to be a good steward of your own business by being profitable.”

The latest introduction to Hi-Speed’s line is Starweigh, a device that delivers the precision performance of a static scale – down to 5 mg -- in a high-speed, in-motion instrument, according to Thomas. Initially used in the pharmaceutical industry, food processor demands for increased accuracy have opened Starweigh to food application.

“It’s like getting laboratory balance into an in-motion packaging line,” says Thomas.

“Everybody wants a faster, better, more accurate checkweigher – and at lower cost,” says Ha Dinh, vice president of engineering for the Alpha checkweigher division of All-Fill Inc., Exton, Pa. (www.all-fill.com). “Your customers also want versatility, easy changeover…machines that are easy to clean and maintain. We try to come up with equipment that meets all these needs.”

An asset management tool

The motivation behind many current sales of checkweighers is their value as asset management and production tools. They help to manage throughput, the amount of saleable product that comes off the production line.

“We are challenged to make sure our checkweighers can keep up with cartoners and other devices in the packaging line or to run them at faster speeds,” says Thomas. “In some cases, it’s trying to get from two lines the production you normally get out of three.”

Managing assets encompasses maintenance and documentation. Cleanability and high washdown resistance are mandatory in the food manufacturing environment since material buildup of any kind can thwart accuracy.

Maintaining a history of an entire product run is vital as well. “Traceability is important in food and pharmaceuticals,” continues Thomas. “In this sense, a checkweigher is an important tool. It gives you an electronic signature on each product.” Hi-Speed’s “S” line, coupled with the available statistical program, supplies security and “checkability,” he says.

“More customers are using checkweighers not only as weighing devices but to make their statistical processes better,” says Thomas.

All-Fill’s Trend Tracker software also has important feedback and control features. “If trending is overweight, the filler will adjust. The same if a package is overweight,” says Dinh. “You can automatically adjust your filler or your conveyor speed, depending on the trend of the production line. And you have a statistical package to see the standard deviation, average fills, the number of good and bad packages that have gone through, along with bar graphs. Your checkweigher can be a quality control instrument that reveals not only how well your filler is working but how well the line is running as well.”

Sophisticated software may enable instant adjustments when a line changes over to run another product. Once all critical control measures for a product have been set and registered, they can be called up instantly, even if the product has not run for two months.

“With the programming capability of our equipment, changeover is usually done seamlessly,” says Loma’s Wilson. “With Ethernet compatibility, you can also tie directly into the data management system of the company. You can change from product A to product B from the manager’s office automatically.”

Hostile environment

Getting accurate weight measure for a package traveling on a high-speed packaging line is, indeed, challenging. Packages moving on and off a scale at rates of hundreds per minute can’t be measured with the consistent accuracy of a single package on a static scale. The speed of a moving package offers little time for a weigh cell to settle before the next package arrives.

The food environment poses natural difficulties to accurate measures with dramatic temperature fluctuations, product mess and dust. High-pressure water in washdown applications poses another serious threat to sensitive equipment.

The strain gauge on the load cell must be protected against moisture and contaminants. The checkweigh area must be clean. Foreign matter and loose product can offset the tare settings. Buildup on platforms and conveyors will compel the scale to re-zero repeatedly. With the sensitivity of the current generation of checkweighers, even drafty air can affect accuracy.

Vibration from a conveyor, hopper or other equipment brings background noise that can interfere with weighing accuracy. The latest generation of equipment attempts to filter out or isolate the scale from such interference.

Loaded for accuracy

The heart of the checkweigher is its load cell, which converts weight or force into electrical signals that actuate measuring. Pharmaceutical applications have demanded greater accuracy than the food industry historically, but profit pressures have turned food processors to reduce waste and giveaway, putting a higher premium on accurate measure.

“We went to a digital load cell over two years ago,” says Dinh of All-Fill. “It has fewer electronic components. Compared to the analog cell, it reduces electrical noise. You are using the same strain gauge load cell, but now everything is done inside the load cell to isolate interference.”

“Most checkweighers are equipped with analog load cells,” says Loma’s Wilson. “Our new AS checkweigher line’s state-of-the-art load cell has nine digital filters that remove background static.”

Promising greater accuracy at faster pack rates, Loma’s FIT (Fast Intelligent Transducer) load cell, produced by sister company HBM for the AS line, features “high torsion and bending stiffness” with outputs of up to 600 measurements per second.

The AS line is also designed to minimize interference from vibrations from nearby machines or the conveyor belt or from air pressure surges. The FIT load cell, unlike analog cells, does not need to compensate for temperature.
Manufacturers of highly accurate checkweighers argue the long-term advantages of accuracy outweigh the cost (or diminished flexibility) of higher-end equipment. Savings from reduced giveaway, waste and rerun accelerate return on investment.

“It’s just like plasma TV,” says Wilson. “People looking to buy checkweighers in the future will want digital load cell technology simply because of the range of features it offers.”

Sidebar: Uses of Checkweighers
Check packages for underweight or overweight filling
Guarantee net contents compliance
Validate the presence of components or package
Check mixes against weight limits
Reduce waste or giveaway by making accurate filler adjustments
Classify product by weight or contents
Helping to fulfill reporting requirements
Measuring and recording the efficiency of a production line
Assuring compliance with customer, agency, regulatory, or other specifications
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