logo_smallFor every cellular glass plant, we have to choose between mold and continuous foaming on an endless belt. In case continuous foaming is chosen, we must decide where to saw the cellular glass ribbon. For float glass, cutting always happens on the cold end and this seems the obvious choice for cellular glass. Indeed, sawing the cellular glass after annealing seems to be the logic choice.

I was surprised to find a patent application US20130145796 where the ribbon is cut between the annealing (550°C)  and the end of the structural relaxation point (450°C). The cutting can be transverse and longitudinal on the cellular glass ribbon. A saw, cutting wheel and knife are suggested.

But why cutting hot? Float glass people are familiar with the famous longitudinal flaw in the ribbon. Regular cutting will stop this flaw in time. Longitudinal cutting reduces the width of the ribbon and in that way, the area stress on the ribbon. In fact, larger temperature deviations are allowed in the lehr without inducing breakage. On the other hand, skilled lehr builder like CNUD-EFCO are able to work within very small temperature deviations.

But there is also an important other reason to work in this way. It allows to anneal the ribbon vertically, reducing enormously the length of the lehr. In this case, an hollow glass lehr is the obvious choice.

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