Melt flow direct gating

For this reason, a pin gate, as shown schematically in Fig. 25 with the melt flow direction for filling drawn in, is useless. Besides, this would also mean an additional weak point at the resulting flow line. 

The change in pressure drop and pressure drop rate at the gate of the mold during the structural foam molding process results in an inevitable nonuniform void fraction along the melt flow direction in injection molded structural foams. The nonuniform void fraction not only reduces the achievable void fraction but also can deteriorate the mechanical properties of structural foams. In this paper, an effort has been made to overcome this problem with various injection speed profiles. 

In this paper, variation in the injection speed profile was used to improve the inevitable nonuniform void fraction distribution along the melt flow direction in structural foam molding. A constant injection speed profile did not resolve this problem, even though high injection speeds marginally increased the void fraction near the gate area. The variable injection speed profile very effectively made the void fraction rmiform. However, the science behind this phenomenon is not rmderstood at present. Further investigation will be carried out to clarify this issue. 

Direct flow through the sprue gate appears to have enhanced filling because the melt flowed directly into the... 

Figure 1 Optical micrograph of a U-shaped hinge after 100 bending cycles, using crossed polars. The highly oriented layers appear dark, the isotropic central layer is bright. One can see the small deformation area not in the middle of the hinge but near to the gate (arrows indicate). The flow direction of the polymer melt is from the right to the left side.

The temperature profiles at different positions along the flow direction are shown as a function of time in Figure 12. After a certain time during the filling stage, the temperature of the melt at positions far from gate is... 

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