![]() The molded article is free of molded in stress normally produced during conventional injection molding, since the process produces a result similar to compression molding.Hesitation marks, shadow marks and permeation all are eliminated since the molded article is full at the time of pressurization.In conventional molding, thin sections require high fill pressures often resulting in a warped part. Thinner wall sections can be obtained since the pack pressure is equally distributed and at significantly lower pressures.Ribs and bosses are fully packed and sink free on the Class A surface finish without the use of gas channels.Hence, it is important to design an ejection system in the mold to prevent ejector pin marks. This pin mark can result in the cracking of the products while in use. Ejector pin marks are either minimized or eliminated since the part is either assisted in ejection by the gas or fully ejected by the gas, in place of ejector pins. Ejector Pin Marks These are are dents left on the part by ejector pins during removal from the mold.This can be beneficial for applications such as in-mold decorating. The process allows pack pressure remote from the material injection point.The process is used to pressurize the article, in place of the pack phase normally performed by the injection-molding machine, and compensate for the volumetric shrinkage during cooling. No pressure drop is realized between gas channels. The entire surface of the molded part is evenly pressured.For more information, visit advantages of the EGM process are as follows: This interactive training program illustrates how “The Circle of Knowledge” between the part designer, mold designer, and process engineers works in the real world of plastic mold and design. offers a state-of-the-art online knowledge and training solution that use 3D process simulation technology to demonstrate cause and effect of molding behavior. For more information, visit Kruse Training, Inc. By using advanced Moldex3D technology, Kruse helps customers troubleshoot from product design to development, optimize design patterns, shorten time-to-market, and maximize product return on investment (ROI). has been providing CAE simulation services to the plastic injection molding industry since 1995. This design would have the highest pressure drop of the three systems and the fewest possible surface appearance defects. Wedged-Round Ejector Pin-Gate System: The wedged-round system has greater thickness at the gate and “wedges” into a smaller thickness at the intersection of the part. Half-Round Ejector Pin-Gate System: The half-round system does not have as low a pressure drop as the full-round system but also has less possible surface appearance issues. However, this style creates the largest witness mark on the part gate interface, potentially leading to small sink marks or surface blemishes. Smaller gates produce higher pressure spikes, overall injection pressures, internal cavity pressures, and clamp tonnages.įull-Round Ejector Pin-Gate System: The full-round system has the lowest pressure drop of the three designs and therefore the widest possible process window. Optimizing sub-gate and ejector pin gate sizes will lead to wider and more stable molding processes and better part quality.As with other gate options, ejector pin gate sizes and styles play a significant role in pressure development during the fill process. The wedged ejector pin runner has a section that is thick at the intersection to the sub gate and then decrease towards the part. There are full-round and half-round runner systems, as well as a wedged version. An ejector pin sub-gate system is a robust automatic de-gating system that will prevent gate vestige.Įjector pin sub-gated runners can have several different design styles. Although many gate systems will leave behind a witness mark, selecting a gate that can be hidden inside the ejector pin with an automatically de-gated sub-gate is an option. Because parts often need to be molded without surface marks or gate vestige, certain gate styles are more appropriate than others. Gate design and placement are key factors in mold design.
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