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.



The right combination between the radiation process and the convection process

In CNUD EFCO GFT annealing lehrs and especially in the radiation area, ambient air is crossing a battery of heat exchangers that avoids any contamination of the glass. As a result, higher quality glass is ensured and a better control accuracy of the process.



Thickness gauge in the hot area

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 data from the annealing lehr help to enhance the production process even further. They are very important for the cold end and specific analysis creates added value thanks to digitalization."

Robert Lamy, Chief Sales Officer at CNUD EFCO GFT


Let us help you create a 'thinking' factory.

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.

Heat is valuable. Why not make full use of it?

Waste Heat Recovery Systems >

An intelligent solution: we transfer the heat that is discharged during the cooling process via pipelines to the warehouse area, where it serves to maintain the required minimum glass temperature during the cold season. At the same time, this reduces heating costs in the warehouse.


Our service for the glass industry

Construction and commissioning of a new glass production line is only the first stage in a good customer relationship. Professional service in daily operation is just as important: We want your investment to be profitable without any interruption – that’s why our engineers are there for you with guidance and support over the entire life cycle of the plant.

More about our after-sales service

Other solutions

Tin bath

Tin bath

The tin bath is the heart of every float glass production line; it is a decisive quality factor. Consequently, at CNUD EFCO GFT, it is always tailored to each customer’s requirements. Using process simulation, we are able to extract the ultimate in yield and quality.

Utilities and central power supply

Utilities and central power supply

For a float glass plant to operate reliably and at peak performance, it needs a steady supply of energy and other media like natural gas, electricity, inert gas, tin and much more.