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Part I : Considering Vacuum Roll Coating

Vacuum Roll Coating

Vacuum rolls (sometimes called vacuum drums or suction rolls) and vacuum belts have been growing in popularity in converting applications. The essential functions of these devices are tension control and/or web metering. But why use a vacuum roll instead of “S” rolls or nip rolls? At what points in a web processing line should vacuum devices be considered? To answer these questions, this overview begins with a description of vacuum rolls and belts. Then useful characteristics of these vacuum devices are listed, and typical applications explained. Finally, a summary of design considerations...
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Part 2: Three Variables That Affect Vacuum Tension Rolls

Web Tension Control with Vacuum Tension Rolls

Vacuum tension rolls and belts provide web tension control by generating a web force against the roll or belt that is independent of the web tension differential (Tension In and Tension Out). The discussion that follows is based on vacuum rolls, but generally applies to vacuum belts as well. Two things happen when the vacuum is applied to the roll. First, the vacuum under the wrap angle creates a pressure difference between the vacuum level and atmospheric conditions. This pressure difference forces the web against the roll and...
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Part 3: Five Benefits of Vacuum Rolls

Vacuum Roll Characteristics

Vacuum rolls and belts have a number of characteristics that are potentially useful to converters. What benefits are derived depends on the application, which will be addressed later. A summary list of characteristics follows.
  1. Single Side Contact - A very popular feature of vacuum rolls is the ability to control tension in a web while touching only one side.
    • No nip is used, so a potential source of injuries is eliminated.
    • Vacuum rolls can transport a wet web, coated but not yet dried or cured, without touching the coated side.
    • Once the coating...
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Part 4: 10 Applications for Vacuum Rolls

The characteristics listed in Part 3: Five Benefits of Vacuum Rolls lead to a wide variety of applications for vacuum rolls and belts for the converting industry. A vacuum roll may replace a standard driven roll to do the same job better, or its unique characteristics may be used to alter and improve a process. For an idea of how some converters have applied vacuum rolls to their advantage, consider the following: [caption id="attachment_2727" align="alignright" width="200"]Vacuum Rolls and Belts Vacuum Roll Coater Dryer Read more

Part 5: Barriers to Vacuum Roll Coating

Vacuum Roll Coating Design Considerations

One simple barrier to Vacuum Roll Coating is that it is more complicated than alternatives. A shell material must be selected and the diameter and pattern of holes in the shell specified. A variety of components are needed to form the vacuum zone within the shell, which may need to be adjustable. A shell coating or covering, chosen from many options, may be required to spread the vacuum, protect the web, or improve the coefficient of friction. Besides the roll itself, a vacuum system is required. This might comprise an...
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