Web materials are not perfect, and neither are converting processes
All converting operations require perfectly aligned material before a critical process. That is the purpose of a web guide system.
Learn more about web guide systems through this summary overview on Web Guiding Principles, Components of all Web Guide Systems, Classifications of Web Guides
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WEB GUIDING PRINCIPLES
The fundamental web guiding principle is governed by the Normal Entry Rule
Normal entry law refers to the propensity of webs to align themselves perpendicular to the axis of the roller it is approaching. This is dependent on the condition that there is no slippage between the web and the roller surface.
Another rule to consider in web handling is a web will track to the largest diameter on a roller. Even though the roller will have a constant angular velocity around its axis, the surface speed of the roller will be higher where the diameter is larger. The web will have higher speed on the part of the roller that has a larger diameter, therefore the web will tend to track to the higher speed side of the roller.
Hence the relative alignment of the rollers and the roundness of the rollers within a roll-to-roll machine play a significant role in the web tracking within the machine.
Web Guide Components
There are three basic elements of a web guiding system
A guide mechanism composed of the mechanical support, rollers, and most important the actuator.
The sensor that detects the position of the web providing feedback to the controller.
A controller that receives the feedback from the sensor and instructs the actuator to displace the mechanism for appropriate correction of the web position.
Intermediate Web Guides
Intermediate web guides displaces or steers the web by changing the axis of rotation of the guide rollers.
Most common intermediate guides are displacement/offset-pivot guides for restricted spaces and usually short span lengths, and steering or remotely-pivoted guides for applications with longer entry span lengths or web surface contact restrictions on one face of the web.
Other types of seldom used intermediate web guides include end-pivoted web guides and center-pivoted web guides.
Examples of locations for intermediate web guides are before slitting, coating, printing, or laminating of a web. or rewind operation of the converting process.
Terminal Web Guides
Terminal web guides are used at the beginning and the end of the manufacturing line, typically at the unwind or rewind operation of the converting process
Unlike intermediate web guides, the whole wound roll is moved laterally for alignment. Unwind guides move to align the web fed into a process while a rewind guide chases the web from a process in order to align the web on a rewind roll.
In both cases the positioning of the web is performed by the physical displacement of the unwind or rewind carriage.
Requires an actuator able to handle heavy loads as it is required to move both the weight of the unwind or rewind carriage plus the weight of the web roll.
Web Guide Selection
What you should consider when selecting the appropriate guiding method
Selecting a web guide is not just about the cost. The width of the web and the configuration of the converting machine are just some of the conditions that must be considered when selecting a web guide
We can help you choose the appropriate guide, but we also offer you the basic considerations for making that important selection
Take a look at our "Tips for web guide selection"