Investigation of steady-state drawing force and heat transfer in polymer optical fiber manufacturing

The force required to draw a polymer preform into optical fiber is predicted and measured, along with the resultant free surface shape of the polymer, as it is heated in an enclosed cylindrical furnace. The draw force is a function of the highly temperature dependent polymer viscosity Therefore accurate prediction of the draw force relies critically on the predicted heat transfer within the furnace. In this investigation, FIDAP was used to solve the full axi-symmetric conjugate problem, including natural convection, thermal radiation, and prediction of the polymer free surface. Measured and predicted shapes of the polymer free surface compared well for a range of preform diameters, draw speeds, and furnace temperatures. The predicted draw forces were typically within 20% of the experimentally measured values, with the draw force being very sensitive to both the furnace wall temperature and to the feed rate of the polymer.