Plastics Design Principles: Unidirectional and Controlled Flow Pattern

By Jay Shoemaker

To produce unidirectional orientation, the filling pattern in the part should be unidirectional. This means the flow direction should be straight and not reverse on itself during filling. In the examples below in Figure 1, the part is rectangular. In the example on the left, the part is gated near the center, and the flow changes direction during filling. It does not have unidirectional orientation. In the example on the right, the part is gated on the right edge and so the flow front lines and flow direction arrows are perpendicular, producing unidirectional orientation.

Center Gated Plastics Flow - Flow not unidirectional	End Gated Plastics Flow - Flow unidirectional
Figure 1: Plastics flow pattern changes with gate location

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