• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.370-375
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• 2002

Recently, the interest on micro optical parts has increased rapidly with the development of technology related to microsystems. Among the optical parts, micro lens is one of the most broadly used micro parts. To mass-produce the micro lenses, it is very effective to use the mold insert and injection molding process. There are many methods to fabricate the mold insert for micro lenses: electroforming, etching, mechanical micromachining and so on. In this study, we fabricated the mold insert for micro lenses using a micro ball endmill to apply mechanical micromaching method and analyzed the effect of main process parameters such as spindle speed, feed rate, dwell time on the processed surface. Then, using fabricated the mold insert we fabricated the micro lenses through injection molding process.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.09a
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• pp.132-140
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• 2005

It is well known that the family-mold has an advantage to reduce the cost for production and mold. However, defects are frequently occurred by over packing the smaller volume cavity during molding, especially whorl the family-mold has a volumetric difference between two cavities. In this study, we confirmed the cavity-filling imbalance by the temperature and the pressure sensors, and developed a variable-runner system for the cavity-filling balance. We carried out experiments fur balancing the cavity filling in the family-mold with the variable-runner system, and confirmed a balanced cavity-filing through analyzing the temperature and pressure change in each cavity as the cross-sectional area of the runner changed. We also examined the influence of the injection-speed to the balancing-capability of the variable-runner system in the experiment.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.119-123
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• 2005

Mold design is a knowledge-intensive decision making process where product designer, injection molding engineer as well as mold designer affect each other. Representation and management of design knowledge is a prerequisite for an intelligent design system, which aims to guide and support designer to carry out design activity in more efficient way by avoiding or minimizing unnecessary trial and errors. This paper discusses the issues in knowledge-based mold design, and describes the structure of a knowledge-based mold design system fur parts with micro features under development.

• Design & Manufacturing
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• v.11 no.3
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• pp.29-34
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• 2017

Increased demand for parts with micro-pattern structure made of metals, ceramics, and composites in various fields such as medical ultrasonic sensors, CT collimators, and ultra-small actuator parts. Micro powder injection molding (PIM) is a technology for manufacturing micro size, high volume, complex, precision, net-shape components from either metal or ceramic powder. In the present study, a standard mold with a variable insert core capable of producing various micro patterns was investigated. An injection molding test was performed on a standard mold using a line type micro-pattern core having an aspect ratio of 2, a slenderness ratio of 70, a pattern size of $200{\mu}m$, and a pattern spacing of $150{\mu}m$. During the filling process, the deformation of the mold with large aspect ratio and slenderness ratio was analyzed by the experiment and the numerical simulation according to the position of the gate. We proposed a mold structure that minimizes mold deformation by gate modification and enables uniform pattern filling behavior.

• International Journal of Precision Engineering and Manufacturing
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• v.2 no.2
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• pp.17-25
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• 2001

In this paper, a theoretical study has been made to reduce the residual stress and birefringence in the injection-molded parts. An optimization program has been used to minimize the residual stresses and birefringence calculated from a simulation program. The thermally induced stress has been calculated using a linear viscoelasticity model. The flow stress and birefringence has been calculated using the Leonov's viscoelasticity model. This has been applied to the injection molding of a circular disc and a plate. the optimization has been done either by changing process variables while maintaining the mold temperature constant or by varying the mold-wall temperature with time. This study shows the significant reduction in residual stress and birefringence is possible through the optimization of processing conditions.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.543-547
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• 2004

The molding characteristics of large-sized orthogonal stiffened plastic plates were investigated in the present study. Models with the geometry of 1800$\times$600$\times$12mm and 1200$\times$600$\times$12mm were designed for injection molding(IM) and injection-compression molding(ICM), respectively. To determine a mold system and reduce the warpage of the presented model after molding process, IM and ICM analyses using MOLDFLOW$^{TM}$ were performed. Also, the experiments were performed to verify the suggested mold system. It was shown that the change of molding method could significant effect on the warpage of designed model.l.

• Journal of Power System Engineering
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• v.4 no.3
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• pp.81-85
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• 2000

The surface gloss of the injection molded part is one of the most significant point for evaluation the quality of products appearance. The effects of molding condition on the gloss of HIPS(High Impact Poly Styrene) molded part were investigated in this work. The measurements of gloss on the surface of molded part were carried out with different melt temperature, mold temperature, injection pressure and holding pressure. We observed the result of HIPS gloss compared with our's previous ABS study. The more melt and mold temperature increased, the brighter the gloss increase. Holding and injection pressure had little effect on the gloss. The gloss was effected in order of melt temperature, mold temperature, injection pressure, holding pressure.

• Design & Manufacturing
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• v.14 no.2
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• pp.42-48
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• 2020

This study is on the injection molding analysis for the LED outdoor lighting top cover of one heat sink body type structure. Thermoplastic and thermosetting resins were applied to compare the thermal properties during the injection molding process. The thermoplastic resin is used in this study due to special characteristics that it is light, good strength and dose long not transmute quality even if pass long time. The thermosetting resin is applied to this study due to good in strength, lightweight and excellent etc, thermal conductivity. This study presented a preliminary analysis of fill time, weld line, air trap etc. for the injection molding process of LED lamp cover and body through simulation using Moldflow. As a result of the study, it was selected HTM-102 material because the thermosetting resin has excellent strength and heat conductivity.

• Transactions of Materials Processing
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• v.15 no.1 s.82
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• pp.65-70
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• 2006

In recent industry, with the miniaturization and high-precision of machine part, the development of mold manufacturing technology for mass production is accompanied by the development of new technology such as IT and BT In this study, the spiral type injection mold with a $200{\mu}m$ thickness is made to. investigating the influence of injection molding parameter and the flow length is measured through an experiment. Besides, Taguchi method is used in this experiment and the obtained data are analyzed using ANOVA method.

• Transactions of Materials Processing
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• v.15 no.1 s.82
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• pp.42-46
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• 2006

For mass production, usually injection mold has multi-cavity which is filled through geometrical balanced runner system. Despite geometrical balanced runner system, filling imbalances between cavity to cavity have always been observed. These filling imbalances are one of the most significant factors to affect quality of plastic parts. Filling imbalances are results from non-symmetrical shear rate distribution within melt when it flows through tile runner system. It has been possible to decrease filling imbalance by optimizing processing conditions, but it has not completely eliminated this phenomenon during injection molding processing. This paper presents a solution for these filling imbalances by using Runner Core pin (RC pin). The Runner Core pin which is developed in this study creates a symmetrical shear distribution within runner. As a result of using Runner Core pin, a remarkable improvement in reducing filling imbalances was confirmed.