Quartz Glass Sagging

Parent Category: Industries

Fused Silica (SiO2) is a synthetic molten, amorphous quartz glass. Quartz glass has an extraordinary high optical transmissivity for ultraviolet light. Due to its low coefficient of thermal expansion, quartz glass can withstand very high operating temperatures. The very good UV-light transparency of quartz glass can not be outperformed by any other industrial glass material. Quartz glass components and fused silica optics are made of large silica glass blocks, called quartz glass "boules". This raw fused quartz glass material can be sawn, ground, polished and shaped according to customers specifications.

Here we present a simulation, done by our meshless CFD simulation software NOGRID points, where a quartz glass cylinder is formed in an oven under its dead weight.

 Meshless CFD quartz glass cylinder
Figure 1: Slumping a quartz glass cylinder

Quartz glass is most commonly heated in an oven and 'sagging' it over a form or into a mold. The glass is heated up slowly to avoid thermal shock. Approximately at the sagging temperature the quartz glass will begin to soften and appear glossy. Depending on the required process time sagging occurs at 100 °C to 300 °C above the sagging temperature. Once the quartz glass has sagged to the final state or the quartz glass has achieved the desired form the heat is quickly vented and the temperature is reduced to prevent further movement of the quartz glass and then it is stabilized at its respective annealing temperature and annealed.

It is also possible to simulate a forming process using different tools to accelerate the forming time.