Product Reviews

Rotary Dies

July 11, 2005

The highly competitive rotary tooling market faces daily challenges from new substrates, new release liners and fast turnaround demands.

.Rotary Dies

Pricewise, they haven’t changed much, if at all, over many years. They are still made of steel, still tooled at the hands of human experts, and still heavy. And people still drop them and knock them around and send them worn out or damaged back to the factory for resharpening.

Until the technology undergoes a major change, rotary die tooling remains an underpinning of the narrow web converting industry. These cylinders, mostly of case-hardened steel, perform the job of cutting — they actually crush the fibers of the substrate — the intricate or the ordinary shapes for which labels are known.

They are precisely tooled to unswerving specifications for two reasons: One, because the customer needs the die to perform with exactitude over tens of thousands of revolutions and powerful impressions in demanding substrates; and two, because the customer’s customer, the end user, requires that the brand’s identity be maintained via its packaging without a molecule straying out of place.

That being said, it is now fair to state that die makers are working feverishly to produce better dies faster and more economically than ever before. The marketplace is relentless. The designs are more unusual, the substrates more challenging, the release liners more delicate, and the customer wants the die yesterday because his customer wanted it the day before. And that’s not all.

“Right now, rotary die prices today — which are charged on a per-inch engraved basis — are almost 25 percent lower than they were seven years ago, for a regular pressure sensitive die,” says Thomas M. Deehr, national director of sales and marketing for Allied Gear & Machine, St. Louis. “At the same time, the costs of steel, electricity, labor and insurance, to name a few, have skyrocketed. Everyone is working on super-thin margins to be competitive on price.”

“We have not had a price increase in rotary dies in well over 15 years,” says Gary Smith, vice president of sales for RotoMetrics, Eureka, Mo. “If you ordered from us today, that die would cost the same as it did 15 or 16 years ago, and it’s a better tool. But the actual cost of producing the tool has increased.”

“With no margins,” adds Deehr, “there is not a real effort out there to make a cheaper die. What we produce is now viewed as a consumable commodity.”

Steel techniques
Though there has been little change in the overall construction of solid die tooling over the years, some changes in the creation process have come along. R&D engineers and chemists have produced coatings that can prolong the life of a die, or give it added protection against abrasives or difficult substrates. There are also different types of sharpening techniques that can produce more consistency, depending upon the application.

Some fairly exotic treatments for steel have emerged over the years. The treating of steel, which requires extremely high temperatures, is now being accompanied in some cases by cryogenics, the subsequent plunging of the steel to temperatures that can go below -300° F.

Basically, dies are constructed from two types of steel. Tool steel is hardened through to the core, while case-hardened steel is hardened to a depth of about a half-inch. In the label converting industry, the majority of dies used are case-hardened. There are, however, more occasions where narrow web equipment is employed to convert other products, such as gaskets or plates out of cork or foam for a variety of industries. These could require tool steel in the dies.

During the heat treatment process the temperature of the die is raised to a point between 1,800° and 2,200° F, depending on the steel. The heat converts some soft internal structures in the steel to harder structures. For case hardening, the die is then quenched in water and shocked into the steel structure desired. For tool steel, the high temperatures are reduced slowly back to room temperature. In the cryogenic procedure, the temperature continues to decline to -300° F or further, thereby hardening almost 100 percent of the internal structures of the steel and resulting in a tool of high grade that will withstand long runs.

Finished dies are tooled by CNC machines to a point, after which the human element is employed.

“The industry still hasn’t found an effective way to finish off a die except by hand,” says Jim Breig, sales manager for Lederle Machine Co., Pacific, Mo. “You’d think that there would be a new process, but there isn’t. Some companies try, but the results are not as high quality as those that are finished by hand.”

The actual cutting part of the die ranges from .020” to .023” above the surface. When the sharpness wears away, or if the die has sustained damage, a few thousandths of an inch can be ground away during the resharpening process to produce a re-usable tool. A die that has not been damaged can expect to undergo three or four resharpenings during its life span. Avis Roto-Die, Los Angeles, customarily leaves .025” to .027” for the cutting edge. “Our customers get more use out of the die,” says President Avetis Iskanian, “usually from nine to 11 sharpenings.”

Another method of creating an intricate die shape is through the use of an electro-discharge machine (EDM). According to Mike Maselli, sales manager for American Die Technology, Suwanee, Ga., the process involves submerging a die in oil, after which an electrical current engraves the image on the die from a distance of a few thousandths of an inch.

“Some people won’t use anything other than an EDM die,” Maselli says.

Challenging substrates, thin liners
“It seems that substrates change on a daily basis,” notes Maselli. “More and more, customers are getting into unusual materials. That keeps it changing and keeps it interesting. There are new foils, new films, and new liners that present challenges. We test substrates all the time on site, and we keep a supply of our customers’ stock or they send it to us.”

“We get in a dozen a month, just to test,” says Breig. “Once in a while we get a couple that just don’t cut, or don’t cut right. But new materials are not really that new, and most of them are knock-offs of others that have been around for a while.”

Abrasive substrates are anathema to the fine edges of steel dies. Growing use of thermal transfer substrates, with their exceptionally abrasive surfaces, means more wear on the steel. The coatings on the papers contain titanium and other chemicals, “and they dull the dies really bad,” says Breig. “But we have learned to deal with them,” he adds. “Thermal transfer materials need a die that is durable. We can lay more chrome on evenly and thicker, and use some special sharpening techniques.

“Sometimes we recommend that they buy two dies,” Breig says, “and they say, ‘What?!’ ”

Die manufacturers are faced these days with a major challenge in the form of thin film release liners used with pressure sensitive film stocks. “The thinner weight of the liner saves money,” says Bob Potratz, sales manager for Action Rotary Die, Addison, Ill. “But it brings some diecutting issues with it. Eventually it leads to a shorter die life.”

“Substrates are getting more and more complicated to work with, especially the liners,” says Iskanian of Avis Roto-Die. “The thickness of the liners is coming down, and that is because of cost. When they make them thinner it brings headaches to the die makers. It takes more time to make it work. It’s mainly economics; I see no other reason.”

Retool and repair
With normal use and good care, a die can easily be re-tooled several times before it is used up. But it never ceases to amaze the die makers that there are some press operators out there who must chew on the dies between meals. Such are the conditions of these sensitive tools when they are returned for repair.

“We have an evaluation department that cleans the die chemically, and checks it for where it is wearing,” says Maselli. “We look to see if there is customer neglect, whether it is running with too much pressure, whether the operators are not cleaning the machine, and whether the die is packing up. We determine the causes and if they are not normal we call the customer and go over ways to extend the die life.”

“It is surprising,” says Smith of RotoMetrics, “how many dies we see damaged from poor handling. It’s an instrument, and it has some really tight specifications. It doesn’t take much to cause damage when you’re talking thousandths of an inch. It can’t take much abuse before the cuttability of the tool is affected.”

Die damage can come from many sources, say Deehr of Allied Gear. “Mostly it’s just poor handling, many times by an operator who has a ring on the hand. Often it is set down improperly on the table, or banged when it goes into the press. Sometimes a foreign particle will go through the press, or even a bad splice can damage the die.”

Jim Breig estimates that 10 percent of die damage is abuse and neglect, the rest being inadvertent or accidental damage.

“It used to be that welding dies to repair them was a very undesirable thing to do,” Breig says. “If it has a big chip in it, then it’s scrap. What we have found at Lederle is a certain way of welding, and in certain cases we can repair a die using a special weld, but only when we deem it to be a good recommendation for that customer’s needs. We can drop a spot of weld on the busted-out area, go back in with a CNC program and re-engrave that area of the die, and grind the top of that area off, not the whole die. We can bring it to where it would be without the chip.”

The company charges for the service, Breig says, “but if the die cost $3,800 and a weld will save it, you’re doing your customer a good service. We’ve become good at it over the past year and a half. Before this, welding was seen as a bush-league type of a rig.”

The fast lane
As if it wasn’t enough that the prices don’t change and the substrates cause headaches, the die makers play “Beat the Clock” on a daily basis.

“The biggest thing is delivery,” says RotoMetrics’ Gary Smith. “It used to be that two to three weeks for a die was the norm. Then it got down to five days, and that was incredible. Now that converters are making their own plates, and using regional slitters and stocking their own inks, the pressure is on the die suppliers. We have made a conscious effort that we are not going to be the weakest link in the chain.”

“They can’t have it fast enough,” says Maselli of American Die Technology. “With multiple parties involved, quick turnaround is essential. In some circumstances, that turnaround is the same day.”

Normal for his company, he says, is 24 to 36 hours from receipt of order to shipment, “provided that there are no unusual or intricate patterns involved, or multiple layers to blade, or a lot of square corners, which take a longer time to mill.”

“Some customers have highly competitive situations,” notes Deehr. “They want to swing a deal with an end user, so they need the responsiveness of a die manufacturer to help them do that. For some customers, and depending on what’s happening here in the shop, I can turn a die around in a day.”