Polymer flow length simulation during injection mold filling

Abstract

The maximum flow length of a polymer for a given set of processing conditions is important in injection molding to avoid incomplete mold filling. Experimental analysis, using various processing conditions, can generate the actual influence of processing conditions on the maximum flow length. However, the experimental determination of the flow length for all known industrial polymers would be time consuming and expensive. A non‐Newtonian, nonisothermal model of mold filling was developed to evaluate the flow length without requiring large amounts of computation time. The model implements the use of both a temperature and shear rate–dependent viscosity as well as viscous heating. This paper presents the model and its numerical implementation, followed by simulation results. The model is compared with other simulation programs and experimental results using both an amorphous Styron 484‐27 polystyrene and a semicrystalline 640I polyethylene in a spiral mold geometry. Good agreement between the three is observed.

Prediction of crystallinity profile and eject time of injection molded parts using finite element method (FEM)

“…[7] ignored the variations in the flow direction to predict the pressure rise and flow length in a slit mold. They assumed that the thickness of the solid layer and the temperature profile change with time, but is constant in the flow direction.…”

“…It is widely used to produce large quantities of various plastic products [1][2][3][4][5]. Therefore it has been studied by many researches from different points of view [6][7][8][9][10][11][12][13][14][15][16][17][18][19]. The major challenge, for the industry, is to design proper molds and select the proper operating conditions to produce high quality products at low cost.…”

Description of second flow field via the deformation of polystyrene phase in high‐density polyethylene matrix

“…In parallel to the intensive studies on the real flow fields in conventional injection moldings (CIM), understanding the complex flow fields in injection molding technologies with a second fluid injection, such as gas‐assisted injection molding (GAIM), water‐assisted injection molding (WAIM) and multimelt multi‐injection molding (MMMIM) has also been of great interest in that it promotes the “structuring” processing of polymers. Their main feature can be summarized as below.…”

“…Moreover, complex interactions regarding stress and heat transfer between the mold, the melt and the second fluid also tend to occur during the molding process. Therefore, due to the great complexity, frequently used methods for CIM process, either numerical simulation (e.g., Moldflow analysis software) or in situ monitoring, is difficult to accurately reflect the real flow fields.…”

“…Combined with eqs. (1)(2)(3)(4), the deformation behaviors of dispersed droplets in blend can be overall depicted from weak to strong shear.…”