The Big Essentials of Tempering Glass

sedak further expands its innovation leadership: Tempering coated glass up to 16.5m

When tempering glass areas up to 50 square meters, sedak's new tempering furnace comes into play. It processes glass with the maximum dimensions of 3.2m x 16.5m into fully tempered or heat-strengthened glass. With this second furnace, the specialist for oversize glass not only doubles its tempering capacities but also enlarges its entire production to a new maximum length of 16.5m. Thanks to innovative technology and sedak's know-how, the new tempering furnace can toughen coated glass in oversize dimensions which means an enormous time and cost benefit. "Our new furnace allows us to expand the status quo and to realize a leap in technology," says Ulrich Theisen, General Manager and Sales Director of sedak.

As modern façade glass has to fulfill ever higher demands on structural physics, coatings for solar and thermal protection become more and more important. Additionally, the trend to very large glass formats persists although the handling and the logistics of them are particularly complex. Therefore, sedak permanently improves its production processes regarding technology and efficiency. A result of that development is the new tempering furnace. It extends the maximum length from 15 m to 16.5 m and optimizes the production process. Coated glass can now be tempered also in the maximum dimensions.

Challenge: coated glass

When tempering in the furnace, the glass has to be heated on both sides evenly. A coating has a major impact on that process. Especially low-e and solar control coatings are difficult to be tempered because they reflect the heat. Hence, the glass heats faster on the non-coated (lower) side and, with the usually used technology, the edges would bend upwards. That effect increases the bigger the glass is. Similarly, the larger the glass, the more probable are anisotropies, roller waves, or color changes. Further damages of the coating can appear due to non-regulated heat distribution which could additionally burn the coating, change its color, or cause cracks. “To achieve the perfect result, it is essential to regulate and control the heat distribution in the furnace exactly, and to adjust it to the specific profile of the glass pane,” explains Theisen. What first sounded simple is in fact a highly complex firing process that requires, besides a high-performance furnace, operating personnel that are very experienced with the raw material glass.

Leap in firing technology

The specification sheet for the new furnace arose from the praxis. For a project in St. Petersburg, sedak had to supply 16.5 m long glass fins. However, the existing tempering line was designed to process glass only up to 15 m. That was the cornerstone of purchasing a new tempering furnace.
Moreover, the previous firing technology was supposed to be improved. “Our ten-year experience of tempering oversize glass was included in the development,“ says Theisen. “It was about improving the regulation and to increase the overall performance.” Tempering coated glass up to 16.5 m is a technical and, in the end, also an economical milestone. With a common furnace, that would not have been possible.
The new furnace is a so-called convection furnace that allows for a quick and exact heat regulation. Also the quenching station, in which the tempered glass is cooled, received a technological upgrade because coated glass reacts faster to changing air conditions. Now, the operators can influence the production process in that part of the machine precisely.

Knowledge is not scalable

To temper coated glass is nothing new. However, the knowledge and the technology cannot be simply transferred from standard formats to oversize dimensions. With every meter more glass, the tempering process becomes more difficult. “Each defect in that step cannot be corrected and worsens during the following production process,” says Theisen. Deviations regarding flatness or shape turn the glass quickly into reject. Hence, it is worth it to put great effort into a perfect production because the result convinces: extremely flat high-performance glass fabricated accurately to a millimeter; glass that is quickly processed into the desired functional glass units. This is the perfect interaction of highly modern machines and experienced glass experts. “Such a precise production would not be possible without the know-how of our operators. They know when they have to adjust the prevailing machine settings.”

Download press release | pdf