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There are many types of anti-wrinkle rollers available to converters. Choosing which is best for removing web wrinkles in your application can be difficult. Here is a concise comparison of several common types to aid in your decision making process:
These rollers have an arced surface and the arc sweeps from the rolls ends out toward the center of the rollers face. So, the rollers ends are smaller in diameter when compared to the center of the roller face. Most of the time, this type of roller is rubber covered.
Generally these rollers are readily available and easy to install. Normally they can be easily mounted in place of standard idler rollers.
The nonlinear roller face causes nonlinear tension across the web as it flows around the roller. Added tension in the center of your web may cause some web distortion. Assuming the web is in traction with the roller face, speed differential across the rollers face may cause wrinkles instead of removing them.
Often times referred to as reverse crown rollers, these rollers have an arced surface like a crowned roll, however, the arc sweeps in from the rollers ends towards the rolls center. So, the rollers ends are larger in diameter when compared to the center of the roller face. Most of the time, this type of roller is rubber covered.
Generally these rollers are readily available and easy to install. Normally they can be easily mounted in place of standard idler rollers. Assuming the web is in traction with the rollers face, the larger roller diameter, toward the rollers ends will drive the web edges slightly faster than the center. Added speed toward the rollers ends will “walk” wrinkles out of the web.
The nonlinear roller face causes nonlinear tension across the web as it flows around the roller. Added tension on the edges of your web may cause some web distortion. This is a passive anti-wrinkle device minimizing the amount of wrinkles removed. Several rollers in succession may be required to remove a moderate amount of web wrinkles.
These rollers may be metal or rubber. They have grooves that spiral out from the center.
Readily available and easy to install, normally to replace existing non-grooved idler rollers. Extremely usefully in higher speed applications to eliminate air entrainment and keep your web in traction with the roller face.
Since wrinkles travel with the grooves they have no effect on pushing wrinkles out of your web. The grooves can cause wrinkle or mark or scratch your web.
These rollers are manufactured with a soft rubber surface. Flexible “lands” flex underneath the web as web tension is applied, pushing wrinkles out of the web.
Useful where air entrainment is a problem. Surface will flex and push wrinkles out of your web.
The flexible lands rely, completely, on web tension to flex. So, the amount of anti-wrinkle aggression will vary as web tension varies. The flexible lands will spring back to their natural position as web tension is removed (where the web exits the roller), this may push some wrinkles back into the web. Some webs may deform in the grooves.
This type of anti-wrinkle system utilizes two sets of nip roller assemblies mounted on each side of your web. Normally, these rollers have a relatively short face and small diameter, each set includes two rollers, spring loaded parallel to each other. Each nip set may include one or both rollers rubber covered.
Utilizing the web handling principal that a web will seek to be perpendicular to a roller in its’ entry span to that roller; each of the webs edges are fed thru each nip assembly. Each of the nip assemblies are angled away from each other. Each of the webs edges will attempt to maintain perpendicularity to each nip assembly, effectively pulling on each edge of your web, removing wrinkles. This type of anti-wrinkle device is extremely aggressive and will remove a severe amount of wrinkles. The amount of anti-wrinkle aggression is easily adjustable. They are relatively inexpensive. Oftentimes trial assemblies are available for you to try in your application.
The nipping action on your webs edges may distort your web.
These rollers are curved. They have a rubber face.
The curved shape of these rollers utilizes the web handling principal that a web will seek to align itself perpendicular to a roller in its entry span to that roller. Properly applied, this roller is an aggressive anti-wrinkle device. It will remove a large amount of wrinkles. They are available in adjustable and nonadjustable versions. This is, by far, the most common type of anti-wrinkle device available to converters. They work well for narrow to wide web, high to low running speeds and you will see them used for all types of materials.
The curved shape may distort some webs by adding tension to the center of your web. Success with this type of anti-wrinkle roller is largely dependent on web geometry. When misapplied these rolls may cause more problems than they solve. Maintenance can be a headache.
These rollers are linear and have a rubber surface, which expands under the web. When measuring the rollers face, it is actually short at one side and longer 180 degrees from the short side.
As this roller rotates the rubber sleeve expands under the web, removing wrinkles. This is the latest, state of the art technology for removing wrinkles. This roller has a smooth surface, which will never mark or scratch your web. Its’ linear surface will never distort your web. It is an extremely aggressive anti-wrinkle device, which will flatten even the most severely wrinkled web. Anti-wrinkle aggression is adjustable from zero to 100% with the use of standard tools, from each end, independently, while the machine is running. So, the operator can actually see wrinkles removed as the roll is adjusted.
High web speeds are a consideration. Maintenance is required from time to time and can be difficult in the field.
This is obviously a very basic, quick comparison of anti-wrinkle system technology. I recommend going here: https://www.converteraccessory.com/papers/index.php for more detailed information about web wrinkles and systems to solve the problem.
Jeffrey Damour, Sales Engineer, Converter Accessory Corporation, Wind Gap, PA
**DISCLAIMER - A great deal of time has been invested in the development of our weekly tech tips. To the best of our knowledge, they are accurate. It is up to the user to verify all results.|
THE AUTHOR ASSUMES NO LIABILITY CONNECTED WITH THE USE OF THIS INFORMATION OR THE RESULTS OBTAINED FROM IT.
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What is Web Handling?
Web Handling is the science, engineering and equipment necessary to successfully transport a continuous flexible material through various processes without defect. Enhancing Web Handling with proper equipment will ensure materials are processed at their maximum efficiency, allowing the process to generate maximum profits.
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