Simulation and Experimental Investigations of Material Distribution in the Sandwich Injection Molding Process

Abstract

In sandwich injection molding, two polymeric materials are sequentially injected into a mold to form a multilayer product with a skin and core structure. Different properties of these polymers and their distribution in the cavity greatly affect the applications of the moldings. In an ideal situation, the core material should be entirely encapsulated in the skin material. When the flow front of the core material overtakes that of the skin material, breakthrough occurs, resulting in a defective part. The focus of this study is to determine the effect of molding parameters on the skin/core material distribution. The commercial simulation package (Moldflow) has been extensively compared with experiments. Both simulated and measured results suggest that in order to obtain the optimum encapsulated skin/core structure in the sandwich injection molded parts, it is necessary to select a proper core volume fraction and suitable processing parameters. A good agreement between simulation and experimental results indicates that the Moldflow program can be used as a valuable tool for the prediction of melt-flow behavior during the sandwich injection process.

Effects of Process Parameters on the Skin/Core Distribution in Co-Injection: Experiments and Simulations Using a Simple Geometry

“…Overestimation of the flow progress is a feature generally reported in the literature [13,18] and is probably related to the oversimplified hypotheses on which the simulations are based. Furthermore, after reaching the maximum, the core thickness fraction decreases in the flow direction, in FIG.…”

“…In a recent article, Patcharaphun et al [18] adopted the Moldflow simulation package to predict the core=skin distribution in a simple part under different process conditions, and compared the predictions of the simulation with experimental results, finding that the two are highly consistent and therefore concluding that the commercial software could be a valuable tool for the prediction of melt flow behaviour during the co-injection moulding.…”

“…Much of the work was devoted to the development of finite volume [13][14][15] or finite element [16] schemes to describe the two phase flow both in sequential and simultaneous co-injection processes, and to determine the final core=skin structure in the part. Some recent contributions check the potential of commercially available simulation packages, such as Moldflow or C-Mold, in determining the flow behaviour during co-injection moulding [17,18] .…”

Visualization and simulation of filling process of simultaneous co-injection molding based on level set method

“…It can be seen that the stress components reach a stable state as times goes on, and the absolute value of shear stress τ xz falls down uniformly from the two horizontal mold walls to the centerline and is considerably larger than that of normal stress τ xx , τ zz Brought to you by | University of Ottawa OCUL Authenticated Download Date | 8/5/15 8:17 PM near the mold walls. Figure 7 shows pressure evolutions versus time at four reference points [P1(1, 2), P2(2, 2), P3 (4,2), P4 (6,2)], from which we see clearly that the pressure values of all of the reference points keep increasing until the mold is filled with polymer melts. The farther the distance from the inlet, the smaller the value of pressure is gained.…”

Process parameter optimization of plastic injection molding: a review

“…Nowadays, many sophisticated software packages are available, which can simulate, analyze, and generate injection molding data based on selected input and output parameters. Numerous works using such software packages have been reported, e.g., Moldflow ® in the fabrication of window frames using rice husk filled polyethylene composites [94], Moldflow ® combined with Autodesk Inventor r for modeling and simulating shallow and flat thin walled molds of a polymer composite [5,6], Moldflow ® to determine significant parameters affecting the shrinkage of molded components [69], Moldflow ® to study material distribution and melt flow behaviour in sandwich molding process [92], Moldflow ® combined with the Taguchi method to determine the optimal design parameters by minimizing the warpage of gas assisted molding components [14], and Moldflow ® integrated with the Taguchi method to study the effects of processing parameters on the molding of ultra-thin wall polymer components [102]. Apart from that, Moldflow ® was applied to some other similar works also, e.g., simulation of feedstock properties for powder injection molding of thermal management devices [86], feedstock properties and injection molding simulations of bimodal mixtures [49], measurements of powder-polymer mixture properties and their use in powder injection molding simulations [48], powder injection molding of ceramic engine components for transportation [61], effects of nanoparticle addition on processing of alloys [85], powder injection molding of parts for UAV engine components [74], etc.…”