Spinning dies turn a profit

Rotary diecutting systems offer speed, versatility, and reliability.

IN THE LAST several years, rotary dies have come a long way. No longer can flatbed diecutting systems claim to handle a substantially wider array of substrates and offer a higher degree of detail than their rotary die counterparts.

Thanks to newer advances like machine sharpening and laser die hardening, and new steels, coatings, and processes, rotary dies have surpassed the versatility and effectiveness of flatbed dies. In fact, rotary dies have a score of benefits to offer printers.

Advantage: rotary dies

Converters are taking a serious look at rotary diecutting systems. They have to.

Time is money in the world of package printing, and presses can effectively print and die cut at speeds of 250 to 800 feet per minute, said Seth Albert, production manager of Action Rotary Die, Inc. (Addison, Ill.). However, Krieg Lee, vice president of operations at Atlas Die (Elkhart, Ind.), has seen rotary dies run as fast as 800 to 1,000 feet per minute.

"There are virtually no speed limitations to rotary diecutting," said RotoMetrics (Eureka, Mo.) Vice President of Sales Gary Smith. "The rotary method will cut and/or crease the material as fast as the machine will run. There may be inherent speed limitations to the machine or other operations within the whole system, but the rotary dies will keep up."

Rotary dies can be made to specific crease-score land widths, and can produce raised score lands, cut-crease score combinations, and embossing. They can also cut and crease just about any substrate out there, barring bulky paperboard material, and they have lead times as short as five days for repeat dies and 10 days for new dies. As long as the converter's volume of parts cut is sufficient, rotary diecutting systems are worth the money.

"Any web operation in the world should seriously consider rotary cutting systems," Lee said. "Consideration should be taken when choosing between solid rotary and flexible plate dies."

Solid vs. flexible

There are two kinds of rotary dies: solid and flexible. Solid dies are made from a single cylinder upon which the cutting design is etched. Flexible or magnetic dies are thin plates that are etched into a cutting pattern and wrapped around a cylinder.

The type of material being run is often the deciding factor between solid and flexible dies. Since the blade thickness of flexible dies is limited, Smith said, they cannot cut through thicker materials with multiple layers.

"Solid dies are also more cost effective when cutting most materials, as they will last longer and are able to be retooled," he said. "While a flexible die costs less than a solid die, a solid die will generally prove more favorable to your bottom line when you compare total die costs for long-running applications."

Smith also noted that solid dies are available with specialty applications, like air-eject and vacuum dies, that allow converters to remove pieces of waste from the web to prevent die damage.

On the other hand, flexible dies permit multiple carton layouts on a single set of mandrels, Lee said. "This equals more flexibility with less capital invested. Large rotary dies can cost $100,000 for a single set of cutting tools. Magnetic cylinders can be purchased for significantly less and allow converters to use them for virtually any layout that will fit the press repeat or sheet size," he added.

When using a flexible die, changing substrates means just changing the flexible die, not an entire rotary die or magnetic cylinder. While a new flexible die is required, the die is a fraction of the cost of a new rotary die or cylinder.

But for the most part, said Frank Hasselberg, vice president of sales at Kocher + Beck (Shawnee, Kan.), "The quality of flexo dies is so sophisticated that you can run any label job, or any job at all. There is no application that it couldn't be used for. The only exception is very bulky material."

Die improvements

Some die manufacturers are starting to machine sharpen and laser harden their flexible dies. The improvements to the dies are astounding.

Machine sharpening of rotary dies can exactly determine the cutting angle that the customer needs for the application. Hasselberg said, "The dies are always consistent. The second die is exactly the same as the first die."

Currently, about 60 percent of the dies leaving Wilson Manufacturing (St. Louis, Mo.) are machine sharpened, said Sales Manager Wade Fouts. Dies with tight tolerances, meaning the cutting surface is even and exact, and a high degree of accuracy are the result of machine sharpening dies every time.

"Our in-house rejection has been reduced drastically," Fouts said. "In-field rejection has also been reduced drastically. It's such a fine, accurate blade, it has absolutely no flaws."

Before machine sharpening, die manufacturers had to sharpen the tools by hand. Fouts likened hand sharpening to sharpening a pocket knife and trying to produce one consistent angle. "You can't do it," he said. "It will have a variety of angles, and some areas are going to dull faster than others. Hand sharpening [of dies] produces the same effect.

"Machine sharpening creates a perfect angle every time. We can guarantee an angle. It's a phenomenon, a real breakthrough in the rotary die business."

Laser hardening is one of the newest die-improving technologies. In this process, a laser is used to harden the cutting line by heating the die to a specific temperature. Once the die reaches the predetermined temperature, the structure of the material is changed, resulting in a longer-life die, Hasselberg said. "For dies used to cut abrasive material, [laser hardening] increases the die life by 100 to 300 percent," he said.

By: Kate Sharon