• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.10
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• pp.34-41
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• 2019

Warpage and weld line are two major cosmetic defects in the injection molding process. These defects are very sensitive to uncontrollable parameters within the process. The optimization of the design variables can be treated with the use of robust designs. Therefore, in order to minimize the warpage and weld line, a special design method to diminish defects is required. In this study, a new robust design method using designer preference to achieve the optimal robust design conditions in the injection molding process is proposed. The effectiveness of the proposed method is shown with an example of the part of warpage and weld line.

• Transactions of Materials Processing
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• v.9 no.5
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• pp.512-525
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• 2000

Designers are frequently faced with multiple quality issues in injection molded parts. These issues are usually In conflict with each other, and thus tradeoff needs to be made to reach a final compromised solutions. The objective of this study is to develop an automated injection molding design methodology, whereby part defects such as warpage and weld line are optimized. The features of the proposed methodology are as follows: first, Utility Function approach is applied to transform the original multiple objective problem into single objective problem. Second is an implementation of a direct search-based Injection molding optimization procedure with automated consideration of process variation. The Space Reduction Method based on Taguchi's DOE(Design Of Experiment) is used as a general optimization tool in this study. The computational experimental verification of the methodology was partially carried out for a can model of Cavallero Plastics Incorporation, U. S. A. Applied to production, this study will be of immense value to companies in reducing the product development time and enhancing the product quality.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.505-506
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• 2006

This study is focused on the manufacturing technique of powder injection molding of watch case made from zirconia powder. A series of computer simulation processes were applied to the prediction of the flow pattern in the inside of the mould and defects as weld-line. The material properties of melted feedstock, including the PVT graph and thermal viscosity flowage properties were measured to obtain the input data to be used in a computer simulation. Also, a molding experiment was conducted and the results of the experiment showed a good agreement with the simulation results for flow pattern and weld line location. On the other hand, gravity and inertia effects have an influence on the velocity of the melt front because of the high density of ceramic powder particles during powder injection molding in comparison with polymer's injection molding process. In the experiment, the position of the melt front was compared with the upper gate and lower gate positions. The gravity and inertia effect could be confirmed in the experimental results.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.25-26
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• 2005

This study suggested the occurrence source of weld-defects and its solution methods in a welding of Electrolyte injection hole by pulsed Nd:YAG laser. In experiment, the ramp down was used in order that solidification crack was removed. Furthermore, shrinkage stress and heat input were reduced by changing of weld trajectory and defocused distance. As a results of a experiment, a sound weld bead shape and crack-free weld bead can be obtained.

• Transactions of Materials Processing
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• v.12 no.8
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• pp.738-743
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• 2003

The major problems of a plastic injection mould can be devided into two kinds, one is in mould another in injected parts. Most of defects of the former comes from mould design, such as, structure and working. The latter are weld line, warpage, sink mark, burning, flow mark, scratching, shading, black hole and so on. Most of problems in injection molding are difficult to find the reason because of complexity. The purpose of this paper is to improve the quality of plastic injection mould and parts with inquiring the counter plan and analizing troubles of the part of Flat TV Front Cover by flow control method and gas-assisted injection moulding. For minimizing defects of the injection moulded parts, computer aided simulation method for injection mould filling was used. Based on these numerical results, the guidelines of mould design and injection processing condition were established. As a result, the improvement of quality, such as minimizing surface defects of injection moulding parts and troubles in mould was achieved.

• Design & Manufacturing
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• v.9 no.2
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• pp.10-15
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• 2015

The water has been the suitable for the cooling medium until now. But the water as cooling medium seem to have the limit for high speed injection. The steam plastic molding injection use the steam as the medium when raise the mold temperature. The weld line has been the major quality problems in a plastic injection parts to be difficult to be solved. These problems in injection-molded plastic parts are difficult to find the reason because these issues are usually in tradeoff realtions with each other. The purpose of this paper is to obtain the optimum injection moulding condition for improving the quality of plastic injection parts and to inquire the productivity improvement with the measured cycle time by steam plastic moluding injection. Based on these numerical results, the guidelines of mould design and injection processing condition were established. As a result, the improvement of quality and the reduction of cycle time was achieved.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.265-270
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• 2000

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

• Design & Manufacturing
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• v.11 no.3
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• pp.13-18
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• 2017

The injection molding analysis of VCM (Voice Coil Motor) housing for smart phone cameras were performed. We conducted the analysis in terms of injection molding pressure, the formation of weld lines, flow marks, and flow patterns. The goal of the analysis was targeted for the prediction of the optimal gate locations. Because the quality of VCM housing is strongly dependent on the precise control of the camera lens by its nature, we focused on the lens guiding lanes in the VCM housing. We first calculated the maximum injection molding pressure in terms of the filled volumes. The injection molding pressure were calculated within 146MPa at about 90% volume filled. We also investigated the possibility of the occurrence of design-related defects such flow marks, weld lines. Filling patterns regarding the design of the gate locations were delineated to find the weld lines. Throughout the simulations, the final deformations of the lens guiding lanes for the VCM housing were calculated. The deformations distribute ranging from $0.5{\mu}m$ to $2.50{\mu}m$, which were used to find the optimal design of the gates.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.5
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• pp.659-665
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• 2011

Recently, the plastic resin such as PC, ABS are widely used in IT market. Especially, in most cases the keypads mounted on the mobile phone are the dual-injection-plated type. Environmental regulation is based on the quality of injection-molded products and the minimum process steps are required to avoid the plating defects. Various parameters to produce the injection-molded plastic products make it difficult to obtain the desired stability. However, the past experience and the use of CAE analysis make it possible to predict the problems occurred in injection molding process. Especially, the problems of the weld lines such as runner balancing, bending, deformation and forming defects can be solved systematically and minimized by CAE analysis. Through this study, the non-uniform volumetric shrinkage and the difference in temperature distribution induce the deformation and the high value of stress causes the problems such as crack.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.252-257
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• 2005

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 in injection-molded products is assessed. And the effects of fiber content and injection mold-gate conditions on the fiber orientation are also discussed.