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Analysis of impingement mixing for coating in injection mold  

Kim, Seul-Woo (Dep. of Aeronautical & Mechanical Design Eng., Korea Nat'l Univ. of Transportation)
Lee, Ho-Sang (Dep. of Aeronautical & Mechanical Design Eng., Korea Nat'l Univ. of Transportation)
Publication Information
Design & Manufacturing / v.13, no.4, 2019 , pp. 1-9 More about this Journal
Abstract
In-mold Coating is a method that can simultaneously perform injection molding and surface coating in injection mold. The material used for coating is two-component polyurethane which is composed of polyol and isocyanate. L-type mixing head can be used to mix polyol and isocyanate uniformly, and inject them inside the mold cavity. The surface quality of the injection molded products by using in-mold coating depends on the mixing uniformity between main agent and hardener. In this study, flow analysis was performed to design a mixing head for uniform mixing of two-component polyurethane. Especially the effects of design parameters of mixing head on mixing uniformity and nozzle pressure were investigated. The parameters of mixing head were mixing chamber diameter, cleaning cylinder diameter, nozzle alignment angle in the horizontal and vertical direction, and cleaning piston position. It was found that optimal design values were mixing chamber diameter of 3.5 mm, cleaning cylinder diameter of 5.0 mm, nozzle horizontal/vertical alignment angles of 140°/160°, and cleaning piston position of 1.8 mm. The optimal values would be used to develop a two-component mixing head achieving an uniform mixing for in-mold coating.
Keywords
Impingement Mixing; Injection Mold; In-Mold Coating; Mixing Head; Polyurethane;
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