Rewinders-A Look at the Future

REWINDERS PLAY AN important roll in today's print shops and can make or break a great print run. For example, registration can be right on the mark, color can be perfect, then Whammo!, during the rewinding process the entire roll can "telescope" into a useless pile of wound-up trash.

"Maintaining uptime and reducing downtime on the rewinder has been a goal for some time," said Brian Ivens, manager, sales and marketing, Arpeco. "Quality of design and manufacturing has always been a significant method of providing reliability and dependability with equipment." There are many reasons the rewinding process can be a problem, but knowing what new technologies are available out there, or knowing some tricks of the trade, can reduce some of the stresses in the print shop.

New technologies

The 2005 holiday season is over. The last of the wrapping paper is thrown out, the remains of the cookies have been eaten, and the last of the champagne has been drunk. And more importantly, your list of New Year's resolutions is complete. And maybe running a smoother converting process is the first resolution on your list. Or at least, near the top right under "eat less cookies and drink less champagne."

Knowing how to improve your package-printing operation involves an understanding of what's available in new off-press equipment. As with almost all technologies in today's world, "new" equipment can usually be boiled down to "more automated" machinery.

Craig Thomson, marketing manager, Martin Automatic, agrees with this statement. The recent advancement in the rewinder industry, "in general, is the level of automation available, especially, the emergence of AC vector drives and motors," he said. Other advances include "differential winding for slit ribbons and, as with all machinery, advances in ergonomics and safety features," he added.

One example of this automation, Thomson said, is Martin Automatic's LRD model rewinder, which now comes equipped with quick-setup slitting, differential (or slip-core) winding, automatic roll unloading, and a lift table to present the slit rolls at a comfortable height.

Another specific example of automation flowing into the rewinder market is CTC International's glueless start version of its "Small Wonder" Automatic Turret Rewinder. This rewinder uses a "unique tucking system to automatically start the winding of small rolls of labels without the need for a core glue," said Rich Herbert, engineering sales manager, CTC International. "This turret rewinder is designed to maximize production time and minimize waste for manufacturers of small label rolls."

Also, Rotoflex International has a line of high-speed inspection, slitting, and rewinding machines, including the VSI series. The VSI series has a long list of standard features, which includes a pneumatic core-type unwind shaft with an auto stop on the roll end. This series also boasts controlled acceleration and deceleration, a hardened web separating idler, an electronic single-edge web guiding system, and manual tension control on unwind and rewind, with automated operation optional.

According to Ken Daming, director of product management, Mark Andy Inc., "Rewinder manufacturers have spent a lot of effort to make the operation of the rewinder as easy as possible by studying the necessary steps in the process and changing the layout of the rewinder to minimize the operator's movement.

"Most importantly," he said, "some rewinder manufacturers have actually looked at the whole press and rewinder workflows and have found more efficient ways to tie in what used to be two separate operations into one seamless workflow. All of these advancements were created to help the converter become more competitive and profitable."

Another new piece of technology that has recently been added to rewinders to improve performance are, what Ivens calls, "productivity assists." "These features include unwind roll lifting systems, automatic fault detection and count sensor set ups, slitting systems with removable cartridges and set-up fixtures, and automatic unwind and rewind roll diameter sensing systems, as well as differential rewinding shafts," said Ivens.

But all of this automation and these advancements in rewinders do not make the system perfect. There is still plenty of knowledge an operator must have to make the entire system run as it was created—smoothly and efficiently—and to stay competitive and profitable in the marketplace.

Where's the ibuprofen?

Oh, the world of converting: full of possibilities, new worlds, lots of money, and, oh yes, headaches. The entire package-printing process is riddled with potential hassles, starting from package design down to the shipping of the finished product—and rewinding is just part of the process. One of the current trends in packaging—the use of thinner substrates—is adding to the challenges in both the press and rewinding processes.

"Today, materials are getting thinner and more delicate, and the web tension management system not only needs to provide constant tension, but also must compensate for the effects of unwind inertial torque and rewind frictional torque, which are typical on center-shaft systems used on most rewinds," said Ivens.

Now one must keep in mind that it is becoming increasingly rare to find a rewinder solely on its own in a press shop. Today, the post-press finishing operation can realistically be divided into two main segments, one being inspection and fault editing, and the second being counting and rewinding. And of course, these operating modes can lead to their own sets of concerns and rules.

"The web must be kept under control at all times (through acceleration, deceleration, and at a constant speed)," said Ivens. "To do this, with driven nip/draw controls for each section, tension variations within one section can be isolated entirely from another and the desired results can be achieved."

There are other, very specific situations that a rewinder operator may come across during a typical rewinding job, including telescoping of rolls, varying rewind roll tension and straightness, and rewind roll straightness. Ivens has offered some suggestions to combat the aforementioned "headaches" in the rewinding process:

• Telescoping: Telescoping rolls are typically caused by inconsistent tension within the unwind or rewind roll. Sometimes, said Ivens, installing a side-support disc to physically restrict the sideward movement of the roll will suffice. Although, he added, incorporating tension management systems into the rewinder is the ultimate answer.

• Varying tension: This can be a result of incorrect torque increase with relationship to rewind roll diameters. Web tension will decrease inversely with roll radius and therefore, Ivens said, torque must be increased to compensate. He offered this formula: Total Torque = Tension x Radius, where total torque is the combination of torque applied to overcome the change in radius, plus frictional torque applied as a result of increasing rewind roll weight.

With many rugged materials, Ivens added that experienced rewinder operators will sense how much and when to increase the applied torque to maintain suitable rewinding results. Ivens warned that as materials get more delicate and exotic, an automatic tension system will provide the best results.

• Roll straightness: Roll straightness can basically be guaranteed as long as all the web guiding equipment is cleaned and that the web guiding system is actuating correctly for the material being processed, said Ivens. And once again, tension is an important factor. "Make sure to not lose tension on the web during rapid machine deceleration as this could cause the web to wander," said Ivens.

Thomson also has some suggestions for press operators to keep in mind when rewinding. "The operator is often expected to get high-quality, low-waste production out of a piece of rewinding equipment that was not designed to handle the substrate, or to meet some other process requirement. This can, of course, be very frustrating. These frustrations can be avoided by consulting with operators, as well as with material and equipment suppliers," he said.

He also laid out some of the responsibilities on the rewind supplier to find out certain information before selling a piece of equipment. Thomson suggested asking questions, such as:

• Is the rewind designed to handle the full range of materials the converter expects to run?

• What tensions does the rewinder need to run?

• Will taper-tension from the winder affect the process?

• Is a lay-on roll required?

• What hardness of roll does the converter's customer requirer?

• Is it equipped with the correct slitting and ribbon separation package?

• What type of finished roll handling is expected?

For now and for good

As with most things in the modern world, people want better, faster, and bigger. That rule also applies to products in the package-printing industry, and companies developing rewinders are taking this into account when they move to the drawing board.

"The new winders offer operators more tunable adjustments that can dramatically affect the quality of a wound roll," said Thomson. "An educated operator now has the opportunity to wind difficult materials, at larger diameters, than older machines would allow. More and more, we are providing rewinders for larger diameter rolls that match the diameter of the unwinding rolls. These are necessarily bigger units and more expensive, given the challenges of winding larger rolls, especially at the increasing speeds of new presses and the abundance of filmic webs."

"In the future, as materials continue to evolve, as quality of the product becomes more important, and as productivity continues to be a key ingredient to increased profits, rewinders will continue to change and become more sophisticated," said Ivens. "Yet the focus will always be to make the machines simple to set up and to use—a combination which is not always easy to accomplish."

by Megan Wolf

Assistant Editor