In this episode of our webinar series on web guiding fundamentals, we explore the installation and operational intricacies of a steering guide. We cover the mechanics of a single roller installed on angled raceways, its bending action, and essential guidelines for entry and exit spans. We discuss the importance of maintaining a 90-degree exit span angle to minimize stress and prevent issues such as wrinkles and web tear. The video also explains the concept of the Instant Center and its role in web guide dynamics, providing installation tips to prevent oversteering and under steering. Join us to learn about maintaining optimal performance and reducing stress in your web handling system.
00:00 Introduction to Steering Guide
00:05 Understanding the Roller Mechanism
00:22 Bending and Displacement in Web Guides
00:41 Installation Guidelines and Stress Management
01:08 Entry and Exit Span Considerations
01:51 The Concept of Instant Center
02:37 Avoiding Common Issues
03:10 Final Installation Tips
Transcript
Show full transcript (631 words)
[Music] The second choice for us would be a steering guide. In terms of how it works, it's a little bit different. You got a single roller. This is the top view and this is the side view.
This roller is installed on two raceways at an angle. The web guide forms an arc like that. It moves and forms an arc back and forth. That's how we are changing the axis of rotation.
In this web guide, we are creating a bending. So there is a bending action here. It's displacing as well as bending. In terms of the entry and the exit span, there are some guidelines for that as well and we'll go through that.
This is not an ideal choice for us because it's bending. So it's introducing stress. If it's not installed properly, it can cause wrinkles, creasing, web tear, and edge stresses. In terms of installation, what do we need to look for?
We need to make sure that the exit span is perpendicular to the plane of motion of the web guide. The main thing is to make sure that the exit span is in pure twist. This allows us to have the least amount of stress in the web. So we want to do that.
Now the entry and exit span length is also depending upon the stiffness of the web. You typically need a longer entry span for a rewind guide because the motion of the web guide or the displacement of the web happens because of bending. So you have to follow those guidelines in terms of if you have a stiffer web, you need to have a longer span so that you can allow the bending to happen. Normally it's about 1 to five times the width of the web.
And then the exit span can be half a web width. And there's also minimum formula for finding out the minimum span length. In terms of other things here, let me talk a little bit about the instance center. Like I mentioned, there is a raceway, two raceways here, and they are angled so that you can have the web guide go around an arc.
And the center of the arc is called the instant center. This is important. We need to make sure that the instant center is within this span. and it's at a certain distance about half the length of the span or up to 2/3 the length of the span.
These are all numbers coming from the dynamic model of the web guide and the dynamics of the web itself. If you don't follow those conditions, then you can have a web guide over steering, under steering, creating an awful lot of stresses, maybe wrinkles, slack edges, tight edges and all those kind of things. The main things that we want to look for is this angle. Make sure that it's 90° and then you have an entry span that is pretty long.
You can have different wrap here. We don't want to go more than 45° on either side. When you do that, you're adding twisting. Uh so whenever it goes away from this 90°, it's not pure bending.
There is bending and twisting in mold there. And then we want to have an angle here because when you put bending stresses here, you have the possibility of what we call as moment transfer. So the motion of this roller can actually move the web upstream of the guide roller. In order to avoid that, we want to have certain conditions here.
And we also want this span shorter so that it becomes harder for that moment transfer to occur. Those are some of the guidelines for installation of a steering guide and again sensor as close as possible. [Music]