• Korean Journal of Materials Research
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• v.3 no.3
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• pp.300-309
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• 1993

Abstract In this work. gasification of graphite cores from nickel-coated graphite composite powders was carried out to munufacture the hollow nickel metal powders which can be used as a raw materials for porous nickel metal strips. Graphite cores were gasified by $H_2O-H_2$ mixture gases at the temperature between $800^{\circ}C$ and $900^{\circ}C$ and nearly all removed from the composite powders within 1 hour. The hollow nickel metal powders prepared from 82.2wt. % Ni-17.8wt. % C composite powders which have the graphite cores of 21${\mu}$m average size were pressed and sintered at $1150^{\circ}C$ for 1 hour in vacuum furnace. The porosities of green and sintered compacts were 45% and 30%. respectively, and pores were distributed very homogeneously in the sintered compact. It was confirmed that pore distribution and porosity in porous materials can be easily controlled by using hollow powders as a raw materials.

• Korean Journal of Materials Research
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• v.11 no.6
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• pp.465-471
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• 2001

The effect of sintering condition on the mechanical properties and leachability of polydispersed ceramic core body made by gel-casting process in aqueous medium have been investigated. The polydispersed ceramic slip that has low viscosity($\leq$1000cP, at 1000cP (at $50sec^{-1}$ ) and high solid loading(50vo1%) was obtained. The green bodies were fabricated through casting and gelation at room temperature followed by drying at $25^{\circ}C$for 48hrs under relative humidity of 80%. Crack-free green body was successfully fabricated through the above process. The strength at room temperature, apparent bulk density, and shrinkage of the ceramic core body increased propotionally with increasing sintering temperature(1100~150$0^{\circ}C$). However, porosity of the ceramic core body showed relatively low vague. Leaching rate of sintered core body increased with increasing porosity of the sintered body, and was significantly dependent upon the concentration of alkali caustic solution at the same leaching temperature.

• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.425-426
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• 2006

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.295-296
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• 2007

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.17-18
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• 2007

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.2
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• pp.67-74
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• 2009

Injection molding have been used for manufacturing various fields of automotive interior trims for years. The demands on the injection molding technique are grown with the further development of the automobile technique and the design presentations for cost reduction and environment-friendly. This paper shows that multi-component injection conditions are different from general injection, also shows how to optimize part design and mold design and how to manufacturing through the efficient use of multi-component injection in development process using core back system. To fulfill this purpose, all influential process parameters related to the quality of automobile parts were analyzed in terms of the correlation between them. Base on that, a innovative process will be developed by injection engineers to implement it in practice.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.7
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• pp.687-692
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• 2015

A mold design for in-mold coating was developed to achieve simultaneous coating and injection molding of an automotive armrest. The developed mold includes one core and two cavities which are composed of a substrate cavity and a coating cavity. The core was attached to a movable plate and two cavities were mounted on a plate sliding in a stationary plate. In a two-step process, the part was first injection molded and subsequently, with the aid of a sliding table, was transferred to a second cavity. The materials used were PC/ABS for substrate and two-component polyurethane for coating. The experiments were conducted by changing the flow rate to investigate mixing characteristics. As the flow rate increased, the mixing improved. Additionally, the bubbles appeared over the substrate surface decreased with an increase of the weight of injected coating material.

• Polymer(Korea)
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• v.32 no.6
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• pp.573-579
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• 2008

PBA/PS core-shell polymer nanoparticles were synthesized by two stage emulsion polymerization and hybridized with silica nanoparticle by simple mixing in emulsion state and following precipitation into water/methanol mixture dissolving $Na_2CO_3$. The stress-strain curve revealed that the elastic modulus was increased with increasing molecular weight of polymer and silica weight fraction but decreased with increasing size of core-shell nanoparticle. Especially, there was a rapid increase of elastic modulus with silica blending. As a result, 6 times higher elastic modulus was observed in PBA/PS core-shell baroplastic sample processed at 25$^\circ$C under 13.8 MPa for 5 min by blending with 13.0 wt% of silica nanoparticle.

• 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.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.1
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• pp.12-18
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• 2009

In this paper, for reducing the assembly torque of subminiature plastic barrel and base which are the essential parts of mobile phone camera module, the high-precision system for inspecting the screw shape of core, electrode and injection molding products was developed. For realization of inspection process, the inspection parameters for evaluating the manufacturing quality were selected and the measurement methods of selected parameters were developed. Finally, the inspection system which is possible to be applied to the field were fabricated.