Core Shift Analysis

Core shift is the spatial deviation in the position of the core from its original position in the injection mold before plastic is injected into the cavity. It is a frequent problem with long, slender, and not necessarily thin-walled products, such as vials, test tubes, pen barrels. It is also experienced often in molds for thin-walled containers.

Core shift can result in undesirable variations in wall thickness which will affect the final shape and mechanical performance of the part. The Core shift simulation provides detailed information about the movement of the mold core and its interaction with the polymer flow process as the plastic is being injected. Designers can use this information to correct for the core shift phenomenon, for example, by modifying the design of the part, or adjusting process conditions such as the gate location or core/mold temperatures.

There are three main causes of core shift:
Inaccuracies in the machining or setting of the injection mold which leads to alignment problems when the mold is closed.
Deflection of the platens or mold plates due to insufficient strength under the high injection pressures experienced during molding.

Deflection of the core as a result of pressure differentials on opposing mold walls. These differentials arise as a result of the gate location or variations in part thickness.

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