High‐Order Pressure–Volume Relationship for Simulation of Stretch and Extrusion Blow Molding Processes

ABSTRACT Accurate prediction of internal pressure during part formation is essential for the simulation and optimization of Stretch Blow Molding (SBM) and Extrusion Blow Molding (EBM) processes, which are characterized by large variations in part volume. In industrial practice, pressure is controlled in the gas supply reservoir, while the effective pressure inside the part is determined by the design of the gas supply lines as well as the large variations in part volume. This work presents a high‐order pressure–volume thermodynamical formulation, derived from fundamental gas energy balance and consistently integrated within the BlowView software's finite element framework. The formulation is assessed through numerical analyses of SBM and EBM processes and validated experimentally using an instrumented stretch blow molding machine. The results demonstrate that the proposed high‐order pressure–volume coupling significantly improves numerical stability, convergence, and predictive accuracy, enabling reliable pressure evolution and thickness prediction under industrial forming conditions. This approach provides a robust tool for machine parameter tuning, blowing power optimization, and reduction of trial‐and‐error adjustments in blow molding operations.