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.
WEB GUIDING PRINCIPLES
Normal Entry Rule governs the fundamental web guiding principle.
Normal entry law refers to the propensity of webs to align themselves perpendicular to the axis of the roller it is approaching; provided 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.
The web will have higher surface 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 is composed of the mechanical support, rollers, and most important the actuator.
The sensor that detects the position of the web provides 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 change the axis of rotation of the guide rollers to displace or steer the web to the desired location.
Most common intermediate guides are displacement/offset-pivot guides for restricted spaces and usually short span lengths. 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.
See our intermediate web guide page for more information.
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.
Terminal web guides require 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 web guide for your application?
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.
Take a look at our Tips for web guide selection page to know the basic considerations.