Modeling the packing stage in injection molding of thermoplastics

Abstract

International audienceA model for the packing stage in injection molding of thermoplastics is proposed. It allows one to calculate the time evolution of pressure and temperature fields and mass variations in simple geometries. The model holds for amorphous as well as for crystalline polymers if the kinet-ics of crystallization are known for temperatures far from the melting point. It applies after filling stage; initial temperature and pressure conditions are available from filling-simulating software. The principles rest on finite difference schemes computing simultaneously temperature and velocity of compressible non-Newtonian fluid in a filled cavity. The pressure field is determined from an equation of state at any time, owing to a mass balance in each gridmesh. The meaningful results of the simulation are local shrinkage and a good approximation of final weights of finished products. The algorithm is essentially checked for the influence of physical, thermal, and processing parameters on the cavity pressure for the injection of a polystyrene (Gedex 1541) into a rectangular mold cavity

Residual stress induced by solidification of thermoviscoelastic melts in the postfilling stage

“…The modelling was carried out initially on the simulation of the filling stage for predicting pressure and temperature distributions, and flow front advancement. Later, analysis was emphasized on the postfilling stage of the process that affects the quality of the moulded parts significantly [1][2][3][4][5][6].…”

Birefringence in injection‐compression molding of amorphous polymers: Simulation and experiment

“…Mold filling during the ICM process is comprised of two stages: injection mold filling of a melt into a partially open mold and subsequent compression mold filling by closing the mold. Inelastic [52–54] and viscoelastic [46, 50, 54–57] simulations of the CIM have been already developed based on the control volume approach [54]. The governing equations for flow of the viscoelastic melt under nonisothermal conditions during the compression stage are presented earlier [57].…”

Birefringence in gas‐assisted tubular injection moldings: Simulation and experiment

“…where T w is the mold temperature, Q ent and p ent are the flow rate and pressure at the entrance node, respectively. To calculate the polymer melt shrinkage due to temperature and pressure variation during the packing and cooling stages, the P-V-T equation of state proposed by Tait [35] was used.…”

“…To solve for the pressure and interface evolution equations (Eqs. [35][36][37][38][39][40][41][42][43][44], the FE/CV/FD approach [15,36] was used. The cylindrical mold cavity was discretized into 216 one-dimensional two-node tubular elements in the length direction.…”