EMEDS: A System to Determine Ejection Layout for Rapid-Tooled Injection Molds

One of the main issues in injection molding is the amount of time required to design and fabricate a mold once a part representation has been created. Rapid tooling methods, the usage of rapid prototyping methods to fabricate molds, have been developed to speed up mold fabrication, but mold design time remains a bottleneck. The design of ejection mechanisms for rapid tools is investigated in this paper. By eliminating elements from a mold that are specific to the molded part, mold design time can be reduced. For instance, the use of a standardized ejector plate with an array of pre-drilled holes significantly reduces part specific elements from the ejector mechanism. The EMEDS system, Ejection Mechanism Design Synthesis, was developed to facilitate the rapid design and incorporation of ejection into rapid tools with standardized ejector plates. Problem formulations and solution algorithms will be presented for the two main elements of EMEDS, the Pin Composer and Pin Locator. In support of EMEDS, an analytical model of ejection force was developed and will be presented here. Application of the EMEDS system to an example illustrates the design of an ejection mechanism for an industrial part.