• Proceedings of the KSME Conference
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• 2001.11a
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• pp.778-784
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• 2001

Injection molding is a very important industrial process for the manufacturing of plastics objects. During an injection molding process of composites, the fiber-matrix separation and fiber orientation are caused by the flow of molten polymer/fiber mixture. As a result, the product tends to be nonhomogeneous and anisotropic. Hence, it is very important to clarify the relations between separation orientation and injection molding conditions. So far, there is no research on the measurement of fiber orientation using image processing. In this study, the effects of fiber content ratio and molding condition on the fiber orientation-angle distributions are studied experimentally. Using the image processing method, the fiber orientation distribution of weld-line parts in injection-molded products is assessed. And the effects of fiber content and injection molding conditions on the fiber orientation functions are also discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.10
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• pp.1575-1582
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• 2001

Injection molding is widely used in producing various plastic parts due to its high productivity, and the demand for injection molded products with high precision is increasing. To achieve successful product quality and precision, the design of gating and runner system in injection mold is very important because it influences the melt flow into the cavity. Some deflects, such as weld lines and overpacking, can be effectively controlled with proper selection of gate locations. In the present study, the design of gate locations in injection molding of a dashboard fur automobiles was carried out with CAMP mold, a PC-based simulation system for injection molding. A dummy runner system was developed to simulate a runner system in order to increase the efficiency of the analysis procedure. The numbers and locations of gates were iteratively determined in the present investigation. In this procedure, an acceptable design was obtained in terms of reducing the maximum pressure and clamping force.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.11
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• pp.961-968
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• 2015

This study aims to develop an efficient mold structure for the injection molding of a subminiature lens, using shell-type runners instead of traditional cylindrical runners. While the shell runner has the advantage of shorter cooling time due to its thinner geometry, this smaller thickness causes an increase in injection pressure. In this study, the design of the shell runner was modified to contain multiple holes for the purpose of reducing injection pressure. Numerical analyses were performed for shell runners of various hole-shapes, and the resulting filling and cooling characteristics were discussed; the rhombic hole showed the best result for both filling and cooling characteristics. Subsequently, injection molding experiments were performed using an injection mold fabricated based on the rhombic design. The lens parts were successfully molded with highly-reduced cycle time and without degradation of part quality.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.9
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• pp.192-203
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• 2001

The design of gate and runner(delivery system) is one of the most important subject in injection molding. Delivery system is a channel to flow the polymer melt from the injection molding machine to the mold cavities. Also, delivery system affect quality and productivity of the part. The synthesis of delivery system of injection molding has been done empirically, since it requires profound knowledge about the moldability and causal effects on the properties of the part, which are not available to designers through the current CAD systems. GATEWAY is a knowledge module which contains knowledge to permit non-experts as well as mold design experts to generate the acceptable geometries of gate and runner far injection molded parts. A knowledge-based CAD system is constructed by adding the knowledge module, GATEWAY, to an existing geometric modeler. A knowledge-based CAD system is a new tool which enables the concurrent design and CIM with integrated and balanced design decisions at the initial design of injection molding.

• Design & Manufacturing
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• v.14 no.1
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• pp.1-7
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• 2020

In this study, the variation of the shrinkage in the thickness direction of the molded parts according to the gate size of the polymer core fabricated through the 3D printer using the SLS method was studied. The polymer cores are laser sintered and the powder material is nylon base PA2200. The polymer cores have lower heat transfer rate and rigidity than the metal core due to the characteristics of the material. Therefore, the injection molding test conditions are set to minimize the deformation of the core during the injection process. The resin used in the injection molding test is a PP material. The packing condition was set to 80, 90 and 100% of the maximum injection pressure for each gate size. The runner diameter used was ∅3mm, and the gates were fabricated in semicircle shapes with cross sections 1, 2, and 3 ㎟, respectively. Thickness measurement was performed for 10 points at 2.5 mm intervals from the point 2.5 mm away from the gate, and the shrinkage to thickness was measured for each point. The shrinkage rate according to the gate size tends to decrease as the cross-sectional area decreases as the maximum injection pressure increases. The average thickness shrinkage rate was close to 0% when the packing pressure was 90% for the gate area of 1mm2. When the holding pressure was set to 100%, the shrinkage was found to decrease by 3% from the standard dimension due to the over-packing phenomenon. Therefore, the smaller the gate, the more closely the molded dimensions can be molded due to the high pressure generation. It was confirmed that precise packing process control is necessary because over-packing phenomenon may occur.

• Design & Manufacturing
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• v.13 no.2
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• pp.17-21
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• 2019

In this study, selective laser sintered 3D printing mold core and metal core were used to investigate the difference of the thickness shrinkage from the gate of the injection molded part at a constant interval. SLS 3D printing mold core was made of nylon-based PA2200 powder and the metal core was manufactured by conventional machining method. As the PA2200 powder material has low strength, thermal conductivity and high specific heat characteristics compared with metal, molding conditions were set with the consideration of molten temperature and injection pressure. Crystalline resin(PP) and amorphous resin(PS) with low melting temperature and viscosity were selected for the injection molding experiment. Cooling time for processing condition was selected by checking the temperature change of the cores with a cavity temperature sensor. The cooling time of the 3D printing core was required a longer time than that of the metal core. The thickness shrinkage of the molded part compared to the core depth was measured from the gate by a constant interval. It was shown that the thickness shrinkage of the 3D printing core was 2.02 ~ 4.34% larger than that of metal core. In additions, in the case of metal core, thickness shrinkage was increased with distance from the gate, on the contrary, in the case of polymer core showed reversed aspect.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.1
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• pp.35-42
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• 2015

Injection molding is a high efficient manufacturing technology for producing plastic parts. On the other hand, the warpage of molded plastic parts is an ubiquitous problem in the injection molding process. The main objective of this study was to minimize the amount of warpage occurring in the injection molding process of a hopper of ATDPS made of crystalline polymer (PP) instead of amorphous polymer (ABS). The moldflow CAE simulation was conducted for the molding process of the hopper to clarify the injection moldability, shear rate, shear stress, warpage by changing the gate shape and the number of ribs installed on the top of the hopper flange. The wide gate shape of runner system and multiple rib installation were found to be useful for minimizing the warpage of the hopper. The validity of the CAE simulations was supported by the injection molding experiment for the optimized design case.

• Design & Manufacturing
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• v.9 no.3
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• pp.9-13
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• 2015

Plastic material has been applied to many automobile parts with the automotive lightweighting trend. In this study, a passenger air bag(PAB) housing which is produced by steel material in the present were molded using a plastics material. Before design and making of a mold for the PAB housing molding, it was carried out injection molding analysis. By analyzing the deformation results, the correction dimension for mold designing was determined. The design and manufacturing the mold applied the correction dimension were conducted. It was performed actual injection molding. The warpage value of the PAB housing was similar to the warpage of the injection molding analysis.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.439-443
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• 2008

Painting process or coating with acrylic film may improve the surface defects of injection molded parts deteriorated by weldlines. flow marks. and etc. However such processes increase the production costs and increase environmental problems. Recently various types of rapid mold heating & cooling technology have been developed in order to improve surface quality of products. In this study. the heating & cooling performance of a telephone case mold is investigated by heat transfer analysis, in which the rapid mold heating & reeling technology is applied. The surface temperature of the mold was measured using thermal image camera and compared with analysis results. The influence of the rapid mold heating & cooling technology on weldline appearance and cycle time increase was also examined.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.9 s.174
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• pp.173-178
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• 2005

Recently plastic parts are molded for the purpose of mass production in multi-cavity system. Therefore, designer is usually designing mold that has geometrically balanced runner lay-out for filling balance at each cavity. Although, mold is manufactured with geometrically balanced runner lay-out, there are actually filling imbalances in the cavities. These filling imbalances phenomenon are caused by complicated interaction between melt and mold. In this study, based on previous studies for filling imbalances in cold-runner mold, filling imbalances in hot-runner mold were investigated by CAE and injection molding experiments. ABS and PMMA as amorphous polymer, PA as crystalline polymer were used to compare the filling imbalances. There were different results of CAE and experiment. The filling imbalances decreased as injection rate increased without regard to kind of resins and were lower than the one of cold-runner.