Simulation of Thermoforming and Blowmolding — Theory and Experiments

The increased use of polymers in the fabrication of various products ranging from beverage bottles, automotive fuel tanks, food trays, to refrigerator liners has made it important that minimum requirements on part thicknesses be met when forming plastic parts. The two primary industrial processes for forming both small and large, thin walled plastic parts are thermoforming and blowmolding. Generally, during these processes, polymers behave in a viscoelastic manner and their deformation process involves large deformations, large strains, large strain rates, contact between the hot polymer and the mold wall, and physical instabilities may also occur during inflation. However, in thermoforming and blowmolding, especially when plug assisted, the process occurs rapidly and at a strain rate high enough for the elastic effects to be dominant and there is no time for viscous dissipation. The polymer undergoes a large elastic deformation.