Ceramic bearings in seaming rolls have made inroads into the canningindustry because they offer long lasting wear performance, improvedlubricant life and corrosion resistance.

From the viewpoint of the can maker, canner, and end manufacturer, searching for ways to reduce manufac-turing costs while improving production quality have always been high priority goals. With the introduction of ceramic bearings into the manufacturing equation, there are distinct possibilities of moving further along the path toward these goals.

Physical properties inherent to ceramic bearings contribute to their long-wearing capabilities, improved lubricant life and corrosion resistance. The presence of silicon nitride translates into a smoother surface and lighter weight than conven-tional bearings. These attributes enable ceramic bearings to operate at lower vibration levels, which in turn produce a longer service life.

A common experience is that standard steel bearings developwear particles over time and adhesive wear build-up eventually produces worn contact surfaces. Wear particles generated by adhesive wear are not present in ceramic balls due to the unique properties of silicon nitride. The benefit to the seaming effort is that less lubrication is required - a cost savings both in lubricant use and time spent lubricating bearings during the seaming process.

"Ceramic bearings may well be the next important element in increasing the longevity of seamer replacement tools"

Corrosion resistance is also a feature of ceramic bearings, compared to steel bearings which have the capacity to corrode over time.

Cost vs benefit
With all of these benefits there is a monetary cost. Ceramic bearings cost approximately four times more than that of steel bearings. At the same time, ceramic bearings are said to last up to five times longer than conventional bearings, depending on the application. The answer to the cost vs. benefit question will vary, depending upon the environment in which the bearings are used.

When considering extending the life of the bearings in a seaming roll by changing to ceramic material, it is important to take steps to extend the life of the seaming roll itself so that all elements have approximately the same wear life. One way to do so is to utilize powdered mould steel such as Stoody or Elmax (highly corrosion resis-tant) rather than stainless steel or D-2 tool steel. Secondly, the application of a surface coating, such as Titanium Nitride (TN), further extends the life of the seaming roll by increasing lubricity and reducing friction and roll wear. When all three elements are present: ceramic bearings, high performance steel, and TN coating, the end user benefits from all of the long wearing options avail-able on the market today.

The beverage industry has been the first of the canners to embrace the use of ceramic bearings in seaming rolls manu-factured with long wearing steel that has been TN coated. Due to the dependence on high-speed canners in the beverage sector, which typically close 1200 to 2000 cans per minute, ceramic bearings have shown to be effective. It is in the food industry, where low-speed seamers are employed (250 to 600 cans per minute) that the use of ceramic bearings has been slower in gaining acceptance.

Jeff Hess, maintenance supervisor at American Nutrition Inc., a pet food manu-facturer headquartered in Ogden, Utah, USA, began using ceramic bearing seaming rolls supplied by Tool Makers International (Santa Clara, California) in January of this year. Mr. Hess commented, "We've been looking for ways to make our tooling last longer on our Angelus 62H seamers. A few years back, our tooling supplier suggested we use titanium nitride coating on our rolls and we've been happy with the improved performance. Then we began using ceramic bearings several months ago and so far have found that the ceramic bearings have lasted much longer than the standard steel bearings. We're still conducting tests to see how much life we can get out of the ceramic bearings." 

As with most tooling, the wear life is dependent on a few factors: the type of product canned and the amount of maintenance performed. When foods are highly acidic, tooling tends to wear faster than when low pH content food products are canned. The caustic nature of high pH foods break down the surface of the tooling prematurely. The type of maintenance performed during canning can also directly affect the longevity of seaming rolls and chucks. If tooling is not lubricated often enough then premature wear will take place. If rolls are not installed properly and the bearings are not shimmed correctly, early wear will occur as well.

Easy-open ends
Phoenix Packaging, based in Canton, Ohio, is a can end manufacturer specializing in easy-open ends for the food and pharmaceutical industries. Since the company's inception in 1993, Phoenix Packaging has focused solely on designing and developing easy-open ends. Jerry Evans, vice president, is currently putting ceramic bearings to the test with a large-scale food canner in the US. "There is a pioneering effort towards gauge reduction to lower the cost of easy-open ends in the food industry," explains Mr. Evans. "We're interested in using ceramic bearing seaming rolls to help our custo-mers minimize cover wrinkle amplitude and reduce scuffing."

Downgauging the weight of both cans and ends presents the challenge of obtaining a smooth seam without scuffing and wrinkles. Jerry Evans con-tinues, "With thinner ends and thinner can body stock, complications crop up. A lighter end stock tends to form a high amplitude cover wrinkle during the first operation, where the cover wrinkle can become tall and sharp. It's diffi-cult to iron out that type of wrinkle during the second operation of a double seaming process." 

At slow speeds, a seaming roll can stop rotating during the brief moment afterone can is seamed and just before the next can comes in contact with the roll. When that happens, the stalling action of the roll can cause friction as the next can comes in contact with the seaming roll. That friction build-up causes heat and can contribute to the deterioration of both the roll and chuck.

Mr. Evans says, "We believe that cover wrinkle amplitude can be minimized because the seaming roll is less likely to stall with ceramic bearings. The reduced friction contributes to less heat build up, which adds to the life of the seaming rolls and chucks. Overall, the ceramic bearings enhance the quality of the first operation seam and helps reduce scuffing and marring as well." 

Phoenix Packaging has taken the position that ceramic bearings should be recommended if end stock is below 75 pounds. The feeling is that the double seam quality will be appreciably better. 

Over the last several years, seamer tooling technology has been continually moving towards improving the wear life of can closing tools. Along with longer-wearing powdered mould steel and high tech surface coatings, ceramic bearings may very well be the next important element in increasing the longevity of seamer replacement tools - a goal worth pursuing.

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