Variational principles were employed to develop the model describing the formation of the bubble, due to internal bubble pressure and take-up force, in such a way that the resulting bubble shape satisfies the minimum energy requirements. The derived equations for the bubble shape (including HDPE wine-glass shape), take-up force and internal bubble pressure have simple analytical forms with only several physical parameters. The proposed model was used in modeling of the film blowing process for a variety of process conditions and polymer melts taken from the open literature, and a very good agreement between measured and simulated data was found. (C) 2004 Elsevier B.V. All rights reserved.