• Journal of the Korean Society for Precision Engineering
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• v.20 no.11
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• pp.41-46
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• 2003

The objective of this paper is to present a methodology for automatically balancing multi-cavity injection molds with the aid of flow simulation. After the runner and cavity layout has been designed, the methodology adjusts runner and gate sizes iteratively based on the outputs of flow analysis. This methodology also ensures that the runner sizes in the final design are machinable. To illustrate this methodology, an example is used wherein a 3-cavity mold is modeled and filling of all the cavities at the same time is achieved. Based on the proposed methodology, a multicavity mold with identical cavities is balanced to minimize overall unfilled volume among various cavities at discrete time steps of the molding cycle. The example indicates that the described methodology can be used effectively to balance runner systems for multi-cavity molds.

• Design & Manufacturing
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• v.17 no.4
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• pp.57-62
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• 2023

As a representative method for mass production, a multi-cavity type mold capable of simultaneously molding products of the same shape can be applied. It has the advantage of improving the productivity from several times to several tens of times, but it may cause disadvantages which is the quality deviation with each cavity. This study, therefore, has tried to increase the cavity filling balance by using a melt flipper and a flow distance control part in the runner part of the mold. Along with this, the design and manufacturing of air vents during injection molding have been verified through experimental methods to achieve a higher level of multi-cavity filling balance and dimensional accuracy.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.381-388
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• 2003

The paper presents our study of development for multi-cavity preform mold system which consists of hot runner system and valve gate. For this purpose, stretching blow molding process and preform injection process were simulated by Polyflow and Moldflow. Based on various results of the preform injection process analysis, process planning was established. The sectional thickness distribution of preform was optimized. Preform injection mold system was designed by these technical analysis data. Finally, 24-cavity preform mold system was successfully developed.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.6
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• pp.117-121
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• 2004

Injection molding is the one of the most important processes for mass production of plastic parts. Usually injection molds for mass production are constituted to multi-cavity runner system to manufacture the more parts at a time. Multi-cavity molds are designed to geometrically balanced runner system to uniformly fill to each cavity. But, when injection molding is performed using a mold with balanced runner system filling imbalances are occurred between the cavity to cavity. The previous studies by Beaumont at. all reported that filling imbalance occurred by thermal unbalance on the mold and viscosity variation of resins and so on. In this study, we conducted experiments in order to know the causes of filling imbalance for 3 plate type mold with 8 cavities. And we exhibited a new so called 4BF mold (4 plate type Balanced Filling Mold) to be possible filling balance. We conducted a experimental injection molding to verify the efficiency of the 4BF mold. In the results of the experiment, we could confirmed the balanced filling possibility of the 4BF mold.

• Polymer(Korea)
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• v.32 no.6
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• pp.501-508
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• 2008

Small injection molded articles such as lens and mobile product parts are usually molded in multi-cavity mold. The problem occurring in multi-cavity molding is flow unbalance among the cavities. The flow unbalance affects the dimensions and physical properties of molded articles. First of all, the origin of flow unbalance is geometrical unbalance of the delivery system. However, even the geometry of the delivery system is well balanced, cavity unbalance occurs. This comes from the temperature distributions in the cross-section of runner. Temperature distribution depends upon injection speed because heat generation near runner wall is high at high injection speed. Among the operational conditions, injection speed is the most significant process variable affecting the filling unbalances in multi-cavity injection molding. In this study, experimental study of flow unbalance has been conducted for various injection speeds and materials. Also, the filling unbalances were compared with CAE results. The dimensions and weights of multi-cavity molded parts were examined. The results showed that the filling unbalances vary according to the injection speeds and resins. Subsequently, the unbalanced filling and pressure distribution in the multi-cavity affect the dimensions and physical states of molded parts.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.752-755
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• 2003

Injection molding is the one of the most important processes for mass production of plastic parts. Usually Injection molds for mass production are constituted to multi-cavity runner system to manufacture the more parts at a time. To uniformly fill to each cavity, multi-cavity molds are designed to geometrically balanced runner system. However. in practice this is not the case. The previous studies by Beaumount at.[2] reported that filling imbalance occurred by thermal unbalance on the mold and viscosity variation of resins and so on. In this study, we conducted experiments in order to know the causes or filling imbalance for 3 plate type mold with 8 cavities. We presented a new so called 4BF mold(4plate Type Balanced Filling Mold) to improve filling balance. We conducted a experimental injection molding to verify a efficiency of the 4BF mold. In the results of the experiment, We could confirmed the possibility of the 4BF mold.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.6
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• pp.64-70
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• 1999

Family injection molding of plastic is widely used to enhance productivity. Runners for molded products in fami-ly injection molding have to be balanced so that each of the producs is filled completely at the same time,. In this study computer simulations were performed to determine balanced circular section runners in family injection molding with two cavities where each of he cavity shapes is like a case. It was found from the computer simula-tions that runner balance could be fulfilled only by modifying runner diameters. But in order to get more quality molded products other process factors such as flow length flow resistance shapes of products and etc, should be taken in to consideration for the design of a family injection molding process.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.451-452
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• 2011

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.4
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• pp.1581-1588
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• 2011

In this study, flow characteristics in a multi-cavity injection molding process were investigated. One of main problems occurred in the multi-cavity molding is a flow imbalance among cavities since it affects physical properties and quality of products. Charge imbalance is caused by the uneven shear stress. Therefore, changes in viscosity affect the physical properties of resin and injection conditions differ in the filling imbalance phenomenon. Through, this study focus on experimental studies of flow imbalance for PC and PP resin occurring in a balanced delivery system. Experimental results were compared with CAE results. By experimental and CAE analysis, main cause for the flow imbalance is temperature distribution in cross section of runner. New runner system with a simple change of runner shape was suggested to avoid the flow imbalance. A series of simulation to confirm feasibility of Volume Runner's effects was conducted using injection molding CAE.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.706-709
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• 2005

Despite geometrical balanced runner system, filling imbalances between cavity to cavity have always been observed in multi-cavity injection mold. These filling imbalances are results from non-symmetrical shear rate distribution within melt as it flows through the runner system. It has been possible to decrease filling imbalance by optimizing processing conditions, but it has not completely eliminated this phenomenon during the injection molding processing. This paper presents a solution of these filling imbalances by using runner core pin which creates a symmetrical shear distribution within runner and the effects on filling imbalance when modifying a shape of runner core pin. As a result of using runner core pin, a remarkable improvement in reducing filling imbalance was confirmed. In addition we investigated how filling imbalances were affected by shape of runner core pin.