• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.05a
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• pp.94-97
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• 2002

Micromolding methods are most suitable for mass production of plastic microlens and lens array with low cost. Among the procedures related with micromolding of microlens array, fabrication of mold insect which contains micro cavity of lens shape is the most important stage. In this study, nickel mold inserts for 45 $\mu\textrm{m}$ and 95 $\mu\textrm{m}$ diameters lens way were fabricated using electroforming process. The mother for metal mold inset was made using reflow method. A micro compression molding with polymer powders was used to test the qualities of the metal mold insets. Micro lens profile and surface roughness was measured by interferometric technique and AFM, respectively. The final molded lens replicated the mother well, and had good surface quality.

• 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.

• Design & Manufacturing
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• v.2 no.5
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• pp.5-10
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• 2008

Recently, ultra precision and light-weight micro products are needed in various industries. Injection molding products with metal insert material is often satisfied with light-weight and precision simultaneously. The researches on macro-size insert deformation have been performed but, a research on micro-size insert is meager. In this paper, the injection molding product with $300{\mu}m$ thin foil insert is designed and insert injection molding process is performed. Finally, the deformation of thin foil insert is analyzed according to insert feature and gate length.

• Transactions of Materials Processing
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• v.20 no.1
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• pp.64-72
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• 2011

In this study, we have investigated bonding of metal and plastic parts with single planar interface. This is facilitated by surface processing of aluminum sheet, which consists of slitting and punching, followed by insert-molding of polybuthylelne terephthalate(PBT). An injection mold has been built to fabricate specimen. After processing of the specimen, tensile and bending shear adhesion tests have been fulfilled according to KS M3734 and KS M3723, respectively. We also have conducted simulation of tensile and bending shear adhesion tests. Based on the tests results, the proposed bonding method outperforms existing methods based on adhesion.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.43-44
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• 2006

The production method of micro sacrificial plastic mold insert metal injection molding, namely ${\mu}-SPiMIM$ process has been proposed to solve specific problems involving the miniaturization of MIM. Two types of sacrificial plastic molds (SP-mold) with fine structures were used: 1) PMMA resist, 2) PMMA mold injected into Ni-electroform, which is a typical LIGA (${\underline{L}}ithographie-{\underline{G}}alvanoformung-{\underline{A}}bformung$) process. Stainless steel 316L feedstock was injection-molded into the SP-molds with multi-pillar structures. This study focused on the effects of metal particle size and processing conditions on the shrinkage, transcription and surface roughness of sintered parts.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.12
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• pp.8-15
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• 2021

Cold forging is a method in which molding is performed at room temperature. It has a high material recovery rate and dimensional precision and produces excellent surface quality, and it is mainly used for the production of bolted or housing products. The lifespan of cold forging molds is generally determined by the wear of the mold, plastic deformation of the mold, and fatigue strength. Cold forging molds are frequently damaged due to fatigue destruction rather than wear and plastic deformation in a high-temperature environment as it is molded at room temperature without preheating the raw material and mold. Based on the results analyzed through FEM, an effective mold structure design method was proposed by analyzing the changes in tensile and compressive stresses on molds according to the number of molds and reinforcement rings and comparing the product geometry and mold stress using three existing mold models.

• Journal of Korea Foundry Society
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• v.13 no.1
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• pp.42-49
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• 1993

Conventional manufacturing process for cast iron-babbitt metal composite is complicate and bimetallic bonding by centrifugal casting is also difficult because their melting point is largely different and nonmetallic inclusion exists on outer shell. This study is aiming to simplify multistage process by adding Cu-powder as insert metals during cast iron solidification. The variables on fabrication of composite pipe are mold rotating speed and inner surface temperature of outer metal. The optimum temperature range for fusion bonding between cast iron and Cu-layer was $1100^{\circ}C-1140^{\circ}C$ in case of mold rotating speed was 700rpm. When the inner surface of Cu-layer was at $900^{\circ}C$, the value of interfacial hardness between Cu-layer and babbitt metal were higher than Cu-matrix by forming diffusion layer, interfacial products between Cu-layer and babbitt metal are proved to be $Cu_6Sn_5({\eta})$by XRD.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.743-746
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• 2000

Plastic microlenses play an important role in reducing the size, weight, and the cost of the systems in the fields of optical data storage and optical communication. In the present study, plastic microlens arrays were fabricated using micro-compression molding process. The design and fabrication procedures for mold insert were simplified by using silicon instead of metal. A simple but effective micro compression molding process, which uses polymer powder, were developed for microlens fabrication. The governing process parameters were temperature and pressure histories and the micromolding process was controlled such that the various defects developing during molding process were minimized. The radius and magnification ratio of the fabricated microlens were $125{\mu}m$ and over 3.0, respectively.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.8
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• pp.1242-1245
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• 2001

Plastic microlenses play an important role in reducing the size, weight, and the cost of the systems in the fields of optical data storage and optical communication. In the present study, plastic microlens arrays were fabricated using micro-compression molding process. The design and fabrication procedures for mold insert were simplified by using silicon instead of metal. A simple but effective micro compression molding process, which uses polymer powder, were developed for microlens fabrication. The governing process parameters were temperature and pressure histories and the micromolding process was controlled such that the various defects developing during molding process were minimized. The radius and magnification ratio of the fabricated microlens were 125$\mu\textrm{m}$ and over 3.0, respectively.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.9
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• pp.112-118
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• 1999

Shrinkage behavior was investigated to obtain more accurate dimensions of injected molding parts for free and restricted shrinkage conditions. various parameters for metal inserted injection process, such as thickness of resin, holding pressure and time, mo이 temperature and restriction condition of mold, were considered for the analysis of shrinkage phenomena. For numerical analysis, MOLDFLOW software was used to find the deterministic parameters of filling time, temperature, pressure and holding time. Also , experimental shrinkage effects were measured through actual injection molding process and the resin thickness was under controlled as 3 mm , 5 mm, and 7mm for the shapes of plastic gear made of Polymide(PA) and Polyxymethlene(POM). The main parameters of these injection processes were found to be holding pressure, holding time and mold temperature in the case of metal inserted molding.