Rewinders and unwinders are critical components to the converting process, since roll-fed converting and printing generally begins and ends with a roll. Regardless of automatic or manual roll changing, printers need sufficient tension control, ergonomic roll and shaft handling, and a reliable operation. They must also be mindful of faster speeds, automation, waste management and meeting the specific needs of each customer.

There are two methods of introducing and removing materials in the converting process. The first is to unwind or rewind material, and the second involves pulling from or returning to boxes.

“Tension control on automatic splicers is important, and in some applications critical,” says Craig Thomson, regional marketing manager at Martin Automatic. “Machine designers must take into account the characteristics of the web, the weight of the roll, the mass of the system, and the capability of downstream press equipment, as well as the set tension and tension control requirements of the process.” 

Tension control is clearly a crucial issue where it is vital that tension is kept consistent throughout the process,” says Chiara Prati, sales manager at Prati Company. “Variable tension will only lead to poor quality, so much of our research is focused on guaranteeing constant web tension through digital control.”

There are several types of winders common to the rewinding and unwinding processes. According to Guy Gil, national sales manager at Chase Machine & Engineering, the most common winders are surface drive, center drive and turret. “Center drive rewinds are best suited for slower speed, narrow, smaller diameter applications like labels or webbing, while surface drive rewinds work well for larger diameter, wider, high-speed applications like paper converting,” explains Gil. “Turret winders are best suited when the converting process cannot be stopped or where roll transfers are required. Turret winders are designed to index an empty core into position once the previous roll has been fully wound. But as one would guess, turret winders carry a great expense and are most commonly used for extrusion lines, when the extruder cannot be stopped.”

Thomson adds that inline rewinders can be single-position – generally the most common – multi-spindle turret winders, and automatic transfer rewinders designed for maximizing throughput on high-performance and higher-speed presses. Single-position rewinders are popular for short runs, where the press will do a limited number of labels before having to stop and change materials, plates, anilox, inks and so on.

In regards to unwinders, single-position unwinds with manual splice tables are common OEM-supplied units and best for very short runs of a roll or less. Turret design flying pasters are often used for film and paper rolls, and they accelerate a new roll to match the speed of the expiring roll before “bumping” the expiring web precisely onto the prepared tape or glue pattern of the new roll to make an overlapping splice. Zero-speed splicers make automatic transfers with both the new and expiring web stopped, using an accumulator or festoon to provide sufficient storage to feed web to the press without stopping or slowing the press during the entire splice cycle.

Like other areas of the narrow web printing industry, rewinding and unwinding equipment has evolved by leaps and bounds. “I visited printing facilities in the mid-90s, where rolls unwound on shafts with wooden chocks, and where constant tension was supplied by a leather belt with a weight at one end draped over the unwinding roll,” says Thomson. “That may have been effective enough for the last century, but we’ve come a long way to reach the high-performance, high-productivity, low-waste levels of unwind and rewind technology required in the 21st century.”

Overcoming Challenges
As with any piece of press equipment, there are certain challenges that must be overcome. According to Thomson, there is a growing emphasis on increasing throughput by increasing process speeds. All the while, material basis weights and calipers continue to decrease. Lighter materials, however, must run at lower web tension levels, which restrict their ability to reach higher speeds.

Suppliers also have to contend with the effects of roller mass, bearing friction, speed changes, and entrained (boundary layer) air.
Martin Automatic also believes that it is important to dispel the notion that one piece of equipment can be applied equally to every workflow. “Martin designs our equipment for adaptability and flexibility, but we recognize that a fits-all solution is seldom in the printer’s best interest,” explains Thomson. “We have engineered and patented a large number of web-handling and automation tools, and we work with converters to create the most appropriate solution for their current and future needs.”

In addition to equipment tailored to a specific converter’s needs, brands must understand how their own rewinding and unwinding processes, and how automatic roll change can benefit them. “As one example, most managers or owners cannot tell us how much material is left on cores on their presses,” adds Thomson. “Much of that core waste can be used and turned into profit with an automatic splicer.”

Product offerings
Martin Automatic offers rewinding and unwinding products to accommodate wider webs, multiple substrates, and expanded printing and decorating options. For narrow web, Martin Automatic has an extensive line of automatic zero-speed splicers and automatic transfer rewinders. Many of its automatic butt splicers are based on the MBS platform, including versions for pressure sensitive labels, unsupported films, paperboards and more to meet press speed and process requirements.

According to Thomson, Martin Automatic offers several rewinder models that are popular in the narrow web field. “The LRD automatic transfer rewinder incorporates winding, automatic roll change, and automatic unloading of finished rolls,” he says. “Many installations integrate web guiding, slitting, ribbon separation and other features. The LRH is designed for larger diameter rolls, such as in lottery ticket and flexible packaging applications.”

The STR from Martin Automatic is a small turret rewinder used in narrow web processes, including food casing and digitally printed labels. Thomson adds that many of the company’s machines that were initially designed in the late 1980s are still in operation today, even outlasting a few presses. “Martin has continually adapted our splicers and rewinders as technology has improved and changed, printing and processing speeds have increased, and materials have become thinner and more extensible,” he says, adding, “Among dozens of new features, Martin has recently made the base model MBS capable of unwinding and splicing many supported and unsupported films, as well as both clear and opaque substrates; introduced splicers with compact designs and special festoon configurations to enable converters to fit automatic roll change into very tight pressroom space; offered laser systems to help the operator position splice tape (on unwind splicers) and cores (on rewinders with multi-ribbon capability) with extreme accuracy; designed automatic unloading options for rolls requiring special handling; and upgraded touchscreen controls on splicers and rewinders for operator convenience and advanced diagnostics.”

AB Graphic has over 1,600 worldwide installations for its automatic turret rewinders. The Vectra Series of winding equipment features servo technology upgrades, allowing for a wide range of substrates. The Vectra is also fully compatible with automatic core loading options and finished roll label application options. The various Vectra models offer different features, including automatic core loading, the choice of slitting/turn bar options and larger diameter roll winding capability.

Aztech Converting Systems offers standard modular unwind and rewind systems. Aztech’s unwind and rewind modules are single-spindle units that will handle roll diameters of up to 40" and roll widths up to 20". They can also handle speeds up to 500 fpm. Systems can be configured to support cantilevered or cradle-mounted rolls depending on roll size, weight and accessibility requirements, and 3 or 6" diameter spindles are available, as well as an option to add after-market core adapters. “The unwind modules are equipped with a heavy duty, dancer-activated disc brake to control web tension. Web guiding with splice table can be added as a system option,” explains Tom Giles, senior account manager at Aztech. “Rewind modules are equipped with constant-torque, or optional powered nip drive or dancer-activated, constant tension control. Rotary shear, crush knife or razor slitting capability can be provided as a rewind system option.”

Chase Machine & Engineering provides a standard line of center drive unwinds and rewinds. The company also designs and builds custom center, surface drive and turret unwinds/rewinds. In the 1970s, it also started manufacturing festooning equipment. “Festooners take narrow webs and fan fold back and forth while traversing the web side-to-side,” explains Gil. “This helps distribute material evenly without twists, tangles or tension. Festooned boxes are also advantageous when feeding materials containing elastic or spandex. The amount of tension  that can be applied to the material while de-festooning can actually be reduced to just the weight of the material itself.”

Chase has enhanced its equipment by improving tight tension and speed control. Its AC and servo drive technologies offer machine builders more control of acceleration, deceleration and speed control to handle a wide range of speeds. “When our standard equipment does not suit an applications needs, Chase offers our customers specialized solutions designed for their challenging application,” adds Gil. “We also offer options such as festooning, when conventional winding equipment is not suited for the application.”

Delta ModTech offers jumbo roll unwinds with roll lift features, low tension unwinding, and unwinds with steering. For rewinding, it offers turret rewinding and differential lane rewinding.  “The design has been proven over and over again so there’s very minimal risk to the customer,” explains Jason Newville, design engineer at Delta ModTech. “We will custom design the winding equipment per the specific application, and we have a great base design to start with. The ability to hold a constant tension on the spindle separates Delta ModTech, and we are also able to unwind low tension applications.”

Delta ModTech can also handle a variety of substrates. “Delta ModTech machines can handle the narrow stretchy materials that require a very low tension,” adds Newville. “Without that control, those materials may stretch by a factor of two at the unwind, and that can create issues trying to feed material into the machine at constant speeds.”

Kocher+Beck offers the UR Precision winding system, which features a servo driven integrated isolation dancer on the unwind that compensates for the time of acceleration required for a new roll of material. This helps avoid changes in tension that can negatively effect the moving web. The five-servo rewinder features a scissor cut for a clean slice, and avoids substrate fold-back with vertical web path to the turret rewinder. The UR also transfers energy from the unwind braking system to the rewind system. The UR Precision 440U provides automatic butt splicing of the leading roll edge of the new roll to the end of the running roll at full process speed.

Prati Company has a range of turret rewinders that are designed to increase productivity. A semi-automatic dual turret rewinder, such as the Saturn MIDI, eliminates downtime related to operating cycle changeover while cutting operating costs. Prati offers a host of solutions to eliminate downtime and increase cost efficiency, such as the Saturn range of slitter rewinders with inspection capability, as well as the recently launched Jupiter WF slitter inspection rewinder for finishing unsupported film, clear-on-clear and SA labels.

Prati’s new generation STARplus is a non-stop glueless turret rewinder, which is suitable for self-adhesive labels and unsupported paper. “Job changeover is completed in three to 15 minutes, saving on downtime,” says Prati. “Productivity is kept at high levels with speeds of 250m/m. Glueless hooking technology for web-to-core fixing saves money and ensures glue-free rolls and a clean working environment, highly suited to pharmaceutical and food label production.”

Jupiter’s exclusive automatic workflow management system, which communicates with workflow link brands, guarantees total reproducibility of each finished roll and totally eliminates human error. “With Jupiter WF, human error is a thing of the past,” says Prati. “By developing STARplus, Prati has perfected glueless hooking technology. High-quality components and premium features such as our FastCut option on slitter rewinders have taken durability into a new dimension.”


Unwind anywhere on (or off) any press
Unwind technology developed during Telstar Engineering’s 22 years has become one of the most important ingredients in the company’s success. As American designers and manufacturers of label press retrofits and converting equipment, unwinding and rewinding capabilities are key to the consistent production of complex labels and converting product operations. With its wide range of retrofit label decorating units, unwinding is an absolute necessity for printers running critical applications such as foil, Cast and Cure holographics, rotary screen and diecutting. For example, unwind and rewind capabilities are a must for producing the most intricately constructed booklet labels on its custom manufactured plowfold units. 

While many of Telstar’s unwinds are designed to simply plug into the press line where needed, other systems involve more complex installations such as bridge mounting, positioning on rails, or even off-line portable unit setups as demand dictates. In special situations where press room space is at a premium Telstar has installed this capability alongside the press between the required stations by engineering turnbars to bring the material to and from the parent press.

Tom Kirtz, Telstar’s president and chief engineer, also credits his company’s early adoption of servo power to the success its broad line of label press retrofits has achieved. “It’s sort of like putting R2-D2 on your press,” he suggests, referring to the Star Wars droid that could operate systems from remote locations. “Servo is like having a smart team of operators at your side during production,” he adds. His company has even added its servo systems and unwind/rewind units when upgrading formerly mechanical-only presses. Kirtz also reports that he has not seen a press brand that couldn’t benefit from his retrofit equipment. “These are some of the smartest money making improvements a printer can make to a press,” he concludes.