Best Practices in Web Guiding
- Published: July 01, 2022
Simple factors can be overlooked, such as proper sensor placement, that is essential for optimal web guide performance which will cause guiding problems. This article reviews correct sensor placement for the four common types of web guides and ways new technology has made it easier get it right.
Typically, webs are guided relative to one edge (edge guiding), both edges (centerline guiding), printed line, contrasting pattern, or an object on the web (line/object guiding).
Unwind guiding
Best practice for unwind guiding places the sensor just after the last shifting idler roller with sensor(s) in the first 1/3 of the exiting web span. If using line/object guiding, use shifting exiting roller to back-up the web to ensure web flatness and maintain proper focal distance from the sensor.
Positive Displacement Guides (PDG)
Also called offset pivot guides or displacement guides, best practice sensor placement is in the first 1/3 of the exiting span. Many PDGs are manufactured with integral sensor mounting. To maintain proper focal distance, a back-up idler roller in the exiting span is required when line/object guiding. The back-up roller and line/object sensor should be located as close as possible to the exiting roller of the guide. The back-up roller must deflect the web enough to avoid changes in the web plane during steering but not so much that it impedes the steering motion.
Single and Double Roll Steering guides
Less common than the PDG type, steering rolls also require the sensor in the first 1/3 of the exiting span. To maintain proper focal distance a back-up idler roller in the exiting span is required when line/ object guiding. The back-up roller and line/object sensor should be located as close as possible to the exiting roller of the guide. The back-up roller must deflect the web enough to avoid changes in the web plane during steering but not so much that it impedes the steering motion.
Rewind Guiding
Sensor placement in rewind guiding is often done incorrectly. Sensor(s) should be placed just before the last fixed idler roller in the process and must move with the winder. Essentially, the winder is “catching” the web as it exits the last roller. For line/object guiding, the sensor also must move with the winder; the last fixed roller is typically used as the back-up. Because it can be difficult to link the sensors to the winder, new sensors with large detection ranges can allow stationary sensors to work in rewind applications.
Following these simple rules will allow your web guides to do their job of eliminating scrap and maintaining quality.
Contact Info:
Paul Henke,
Vice President Sales, Web Guiding
This email address is being protected from spambots. You need JavaScript enabled to view it.
