Nonlinear Core Deflection in Injection Molding
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Authors
Poungthong, P.
Giacomin, A. Jeffrey
Saengow, Chaimongkol
Kolitawong, Chanyut
Liao, H.-C.
Tseng, S.-C.
Date
2018-02
Type
technical report
Language
en
Keyword
Injection molding , Thin-wall injection molding , Core deflection , Core bending , Race tracking , Core deflectability
Alternative Title
Abstract
Injection molding of thin slender parts is often complicated by core deflection. This deflection is caused by molten plastics race tracking through the slit between the core and the rigid cavity wall. The pressure of this liquid exerts a lateral force of the slender core, causing the core to bend, and this bending is governed by a nonlinear fifth order ordinary differential equation for the deflection that is not directly in the position along the core. Here we subject this differential equation to 6 sets of boundary conditions, corresponding to 6 commercial core constraints. For each such set of boundary conditions, we develop an explicit approximate analytical solution, including both a linear term, and a nonlinear term. By comparison with finite difference solutions, we find our new analytical solutions to be accurate. We then use these solutions to derive explicit analytical approximations for maximum deflections, and for the core position of these maximum deflections. Our experiments on the base-gated/free-tip boundary condition agree closely with our new explicit approximate analytical solution.