Cavity Effect on Core Penetration in Co-Injection Multi-Cavity Molding

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Title:	Cavity Effect on Core Penetration in Co-Injection Multi-Cavity Molding
Authors:	Chao-Tsai (CT) Huang;Chih-Chung Hsu;Rong-Yeu Chang;Shi-Chang Tseng
Keywords:	co-injection;multi-cavity;core penetration
Date:	2016-05-24
Issue Date:	2016-08-15
Abstract:	Co-injection molding is commonly used in daily accessories, car parts, and structural-reinforcement product. However, there are too many combinations of designs, materials, core/skin ration, and process condition, how to have suitable control of co-injection is very challenge. Furthermore, co-injection with multi-cavity system is also utilized in some forks structure products. Due to the complicated nature, the inside mechanism of the multi-cavity co-injection system is still not fully understood yet. In this study, we have proposed three kinds of multi-cavity systems to investigate cavity design influence on the core material penetration behavior. In Model 1, it is a three separated cavities system. Although the flow rate can influence core penetration during early history through the runners, the separated cavity structure will restrict the core development in Cavity 1. Then it ends up with a non-uniform skin/core distribution in presence of different flow rates influence. Moreover, when it has a different thickness of connection between cavities in Model 2 (with 3.5 mm thick connector) and Model 3 (with 1.75 mm thick connector), during the early filling age (less than 90% of total volume filled), it is Branch 2 dominant in Model 3; while in Model 2 it has no preference for Branch 1 and 2. The flow rate conditions have no significant effects for core penetration in this period. However, as more melt keeps flowing into cavities till the end of filling, the core penetration behavior is dramatically different at low flow rate (say 10 cm3/s). These results show that in the presence of different thickness of connector, the penetration history and final shapes of core layer are significant different to that of separated cavity system (Model 1). Obviously, cavity design can alter the preference of core penetration from one side to the other. The results can help people for the management of skin/core distribution in co-injection molding.
Relation:	SPE ANTEC Indianapolis, p.1040-1044
Appears in Collections:	[Graduate Institute & Department of Chemical and Materials Engineering] Journal Article

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