This week we’re covering the following question related to glass lamination:

How many nip rolls do you need in a laminating line?

That’s a question that we get a lot in relation to glass lamination. Often, you will immediately get the answer that you need to have two nip rolls. This is because for a very long time laminating lines have been equipped with two nip rolls. And it is very easy to take that as a given. If you’ve seen this in so many places, you assume this is how it has to be.

But first of all, it is good to understand what is the job of the nip rolls, and why you would want to have two.

So, if you think about what you want to achieve with the help of the nip rolls, the first thing is removing air out of the laminates. So, basically, you are pushing air through the leading edge towards the trailing edge and then out of the trailing edge. And the second job is creating preliminary adhesion between the interlayer and the glass.

Why we often see two nip rolls in the laminating lines is related to the most common problem that we encounter in the laminating process – trapped air around the trailing edge and the glass. And what is causing this is that traditional infrared furnace tends to overheat the trailing edge of the glass. With this, when you are trying to push the air outside of the trailing edge, there is no way for the air to go if it is trapped. This is why adding a second nip roll is sort of a work-around for this problem. But in fact, it means not addressing the root cause, which is inaccurate heating, but getting a tool to cope with the existing problem and produce the acceptable quality.

But basically, if you are able to heat the glass accurately enough to the correct temperature, there is no need to do this kind of de-airing with the first nip roll.

Modern heating systems, such as Glaston ProL, offer the tools to heat the glass to the needed temperature and do everything with just one press. It basically streamlines the process and makes everything much easier.

So, the answer to the question is related to the heating technology that you are using. If you are using outdated technology with inaccurate heating, you definitely need two nip rolls. Otherwise, you won’t get the acceptable quality out of the line. But if you are using modern technology that provides you the capability to heat the glass to the correct temperature, then using one nip is just fine. Besides, it provides you with such an advantage, as saving some floor space. And it also means that you won’t run into a situation when a long glass pane appears under two nip rolls at the same time, which can cause an issue itself.

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