Fluent software simulates all phases of the various types of blow molding: Extrusion blow molding (EBM), injection blow molding (IBM), stretch blow molding (SBM) and 3D extrusion blow molding. For EBM, this includes the parison extrusion stage, with moving mandrels if desired.

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The blow molding simulation of a 1-gallon milk container, including the parison extrusion, pinch-off, mold closing and inflation stages

The extrusion, injection and stretch blow molding processes can be broken into four stages: extrusion, pinch-off, blowing and cooling. Each phase presents numerous design challenges which can be addressed with flow modeling and analysis. The central challenge is to achieve uniform thickness.

Once the parison is extruded, the quality of the welding line is critical to ensure proper permeability. For automotive gas tanks, the pinch-off of the multilayer parison is regularly simulated to make sure that EVOH layers are not squeezed out of the pinch-off region, as this would result in unacceptable gas leakages.

In a multilayer pinch-off the thin impermeable layer (dark blue) may disappear from the welding line depending upon the operating conditions

The most impressive phase of the blow molding process is the blowing stage during which the extruded or injected parison is inflated inside a mold to give it its final shape. Issues such as local thickness, velocity, area stretch ratio, permeability and temperature are routinely calculated. Fluent's CFD software gives you invaluable insight in to the blow molding process of your container production.

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Simulating the final wall thickness distribution in the blown part helps to identify areas that are too thin (leading to structural weakness) or too thick (wasted material)