The annealing lehr

Once it leaves the tin bath, the glass ribbon enters an up to 200 meter, or approx. 656 foot annealing lehr. This is a kind of long kiln in which the glass is cooled slowly from about 600 degrees Celsius or 1,112 degrees Fahrenheit to 60 degrees Celsius or 140 degrees Fahrenheit. This controlled cooling process minimizes stresses in the glass, which is vital when processing the glass afterwards.

Therefore, the annealing lehr has a very important role to play. A CNUD EFCO GFT annealing lehr will contribute to a stable glass. In the closed part of the annealing lehr, heat exchangers are used to prevent cooling with ambient air, which prevents contamination during the process and, in turn, ensures better quality glass. We draw on a customized calculation program with a good, decades-long track record and our expertise from 40 years of annealing lehr technology.

In CNUD EFCO GFT annealing lehrs, ambient air and process air are separated using heat exchangers – a crucial advantage, because the process air is drawn through the heat exchanger, preventing “bad air” from being blown into the process and causing contamination. As a result, higher-quality glass is ensured.

Our thickness gage in the hot end measures the thickness of glass ribbons right at the beginning of the annealing lehr. As a result, feedback relevant to the production process is fast. Any deviations from specifications are corrected and resources safeguarded.

• Combined measurements including temperature, glass ribbon width, glass position

• The gage can be retrofitted, even when the machinery is running

The future of the glass manufacturing industry is digitization, which means that all stages in the process not only deliver and process data, but also communicate with each other. That’s what we call smart production.

Thickness measurement in the hot area and two-sided temperature measurement are just two of the features involved. The measurement of the glass ribbon’s width offers an additional advantage: by combining the drawing speed of the annealing lehr with the thickness and width of the glass ribbon, it is possible to calculate the tonnage precisely. And by measuring the glass’s position, ribbon swing can be detected and corrected at an early stage. Moreover, the data from the annealing lehr generate conclusions for the entire production process, particularly the cold end. This data gathering and analysis and the resulting conclusions offer real added value for glass producers.