Product Showcase: Tensioners and Guides - March 2014

Tensioners and Guides
Tensioners and guides help substrates pass through an 
array of driven and idler rollers, past web treatment, coating and/or slitting stations, and then wound into a master roll. Speed may need to be controlled within a fraction of a percent for precise treatment or coating uniformity. Active tension control is required to maintain traction with the idler rollers and avoid scratches, stretching, tearing, wrinkles and creases. Successful web conveyance requires matching process conditions and machine hardware to the web characteristics. For example, substrate properties should be considered when optimizing conveyance for the web material, be it paper, film or foil. Some of the most critical factors for optimal web conveyance include:

Tensile Strength: The maximum stress or force per unit area that a material can withstand while being stretched or pulled before failing or breaking. Note that the substrate strength may change after a coating is applied, especially for papers that absorb liquid, which can weaken the fibers.

Tear Strength: How well a material resists the growth of cuts or nicks while under tension. Some materials tear easily like thin papers. Others are so tough they will bend rollers and break shafts before the web breaks.

Dynamic Coefficient of Friction between the Web Material and Roller Surfaces: Air flotation may occur at low tensions and/or higher speeds depending on the surface finish of materials and rollers. Loss of traction causes scratches, guidance and drive control issues.

Edge Curl: Some substrates will curl at the edges when under tension or when wet from a coating solution. This curl can cause guiding challenges and may increase the risk of a web break.

There are far more details in web control than space here allows. Some of the current offerings for package printers and converters are included in this section.

Thanks goes to Gary Kirkpatrick, P.E. Senior Manufacturing and Reliability Engineer, and Todd Arndorfer, Business Development Manager, Carestream Tollcoating for providing these details that need to be top of mind when controlling a web.

Fives North America
Fives North American Guiding Systems designs products and customized systems for label presses, die cutters, packaging and bottle labeling machines, and more that reduce material waste, improve product quality and increase process line speeds. Applications include unwind and rewind guiding control, intermediate web guide control, and turnbar guiding.

Fives North America’s newest offerings include the H6421 featuring:

• 24vDC web guide controller and operator interface in one compact package
• Edge or center guide control for applications requiring 60–300 pound thrust electro-mechanical actuator Ideal for compact locations or small footprint machines

New medium-to-wide web controllers with:

• 110vAC or 220vAC web guide control
• Independent operator interface for optimal install location
• Edge or center guide controls for applications requiring 60–2,000 pound thrust electro-mechanical actuator

Both employ the company’s SimPlex technology featuring plug-and-play components, automatic one-touch setup, and operator keyboard lockout. http://fivesna.com/

Maxcess
The new Digital Load Cell Amplifier (DLCA) from MAGPOWR is a versatile, low-cost, yet powerful DIN rail mounted digital amplifier that provides tension reference to a drive or PLC for displaying or controlling tension. The new DLCA multiplies a millivolt tension signal to a usable 0 to 10 VDC and 4 to 20 mADC analog output. It features one pushbutton for re-zeroing, programmable filtering of each output, three pushbuttons for easy setup and calibration, weightless load cell calibration, configurable alarm output, and automatic load cell diagnostics and fault indication. magpowr.maxcessintl.com/

Quantum Design
Quantum Design, formerly Keene Technology, offers the MR Series Turret Rewind available in either 3 or 5 roll configurations to continuously wind rolls without stopping for roll removal. The machines utilize the zero-speed concept which means the web is brought to a controlled stop at the time of the transfer. The key to making the zero-speed transfer is the use of a storage festoon which serves multiple purposes.

The festoon (accumulator) stands between the press and the winding spindle and feeds press speed information to the MR control system. During the splice, the winding spindle is brought to a controlled stop. The festoon accepts paper from the press during this deceleration and stores it. After the web is secured to the new core, the festoon depletes storage and prepares for the next transfer without slowing down the process line.

Numerous options allow the customers to “build” a machine to meet specific requirements including:

• 16”, 20” and 24” ww
• 1” - 6” core capabilities (dependent on model)
• Integrated festoon allows transfer at full line speed
• Speeds up to 800 fpm
• Automatic spindle inflate and deflate
• Options include shear cut slitting, automatic web gluing, cut between labels, and end of roll web marking.

http://www.keenetech.com/http://quantumdi.com

Erhardt+Leimer
Erhardt+Leimer’s web guiding equipment uses a digital zoom on its ELSCAN system to switch imperceptibly between two cameras, allowing for delay free zooming and navigation. Any section of a repeat can be quickly displayed, and a simple click on point on a given point will move the camera to this position allowing the print quality to be checked as quickly as possible.

Erhardt+Leimer’s EL-WMS spots defects like edge tears, large holes, alerting operators with timely alarms to prevent rejects and identify the causes. http://www.erhardt-leimer.com/

Martin Automatic Tension Control Systems
Web tension upsets between a roll and the process may be caused by braking of the running roll, splicing action, acceleration of the new roll after splicing, and out-of-roundness or imbalance in the roll. A dancer system using the principle of inertia compensation effectively absorbs tension upsets and delivers constant web tension to the process. Inertia compensation is achieved by engineering the system components to balance the translational (up and down dancer motion) and rotational (rotating dancer motion) inertias. Martin Automatic applies this patented principle in all its tension control and splicing equipment.

Martin offers constant tension infeeds and outfeeds and for accurate control in web processes. Features include AC vector drive, positive nip and inertia compensated dancer. Systems may also integrate web guiding, decurling, web turning or other components.

A Martin zero-speed splicer includes a festoon (accumulator) which not only supplies web to the process at full speed during the splice cycle, but also utilizes inertia compensation to absorb tension upsets. Martin accumulator and dancer systems are retrofittable, both as a means of increasing the speed of existing processes and for improved web handling of lighter or thinner materials.

Martin’s MDR (magnetically driven roller) and patented Airnertia roller solutions are other approaches to transporting web material. MDR technology is used on web transport rollers to reduce or eliminate the effects of roller mass, bearing friction, speed changes, and entrained (boundary layer) air. Airnertia offers web transport rollers with reduced moment of inertia.

Both technologies are modular so they can be used within all process equipment utilizing rollers for web transport. Either may be well suited for applications requiring high speed, low tension, high acceleration and/or deceleration rates, and reduced physical size of equipment. Benefits include improved web handling for reduced waste and increased productivity. http://www.martinautomatic.com/

Dover Flexo Electronics
The EasyWeb Torque controller from Dover Flexo Electronics is an open-loop system for maintaining tension on package printing and web finishing lines. The controller, which works based on a diameter calculator signal, is a lower-cost alternative to the highly precise transducer-based tension controllers for applications that require less web tension precision. Unlike Dover’s tension controllers that take an input signal from tension transducers (load cells), web tension with the EasyWeb is maintained by controlling motor or brake torque based on the calculated variation of roll diameter as the roll is wound or unwound. An inertia compensation parameter is provided to obtain greater control of web tension during changes in line speed.

The EasyWeb Torque Controller can accept input signals from a direct diameter sensor or can calculate diameter using line and roll speed signals. In addition, an automated option is available to alert machine operators to the moment that a roll’s unwind or rewind is nearing completion. An automatic shutoff feature can be enabled to shut the machine off when the core is reached at unwind or when full roll is reached at rewind.

Finally, maintaining web tension is critical to print quality and maintaining this quality requires constant vigilance. To help with that task while maintaining productivity is the job of other tools that can activley monitor web performance and alert operators to any trouble. http://www.dfe.com/