A Numerical Study of Fiber Glass Drawing Process

The industrial glass fiber process is very sensitive to disturbances as they can lead to fibers break during the extrusion step. To identify and better characterize the relevant underlying physics and the possible causes of fiber break, the glass behavior from the die exit to the winder is investigated numerically. In a first step, simulations of the glass fiber extrusion process are performed where the fluid is considered Newtonian. The full Navier-Stokes equations including the energy equation for the temperature are solved with a finite-element method. The solution is then compared to previous results from the literature. In a second step, we conducted a sensitivity analysis of the key process variables, such as glass height above the tip, viscosity and flow rate at the tip exit, winder velocity... Additionally, the importance of an accurate physical representation of the heat transfers, i.e., conduction within the fiber, radiation of the fiber, and convection around the fiber, is investigated. This model shows very good agreement with cases from the literature. It was found that bushing temperature and fiber environment have a significant impact on forming fiber shape. This demonstrates that numerical simulations can provide a useful tool to adjust the process operating window.