• 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.

• Korean Journal of Metals and Materials
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• v.49 no.1
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• pp.32-39
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• 2011

The present investigation was performed on the die compaction and sintering behavior of Fe micro-nano mixed powder with a mixed binder for powder injection molding. Warm die compaction of the feedstock for simulation of the static injection molding process was conducted using a cylindrical mold of 10 mm diameter at $100^{\circ}C$ under 4MPa. The die compaction of the micro-nanopowder feedstock underwent a uniform molding behavior showing a homogeneous distribution of nanopowders among the micropowders without porosity and distortion. After debinding, the powder compact maintained a uniform structure without crack and distortion, leading to a high green density of 64.2% corresponding to the initial powder loading of 65%. The sintering experiment showed that the micro-nanopowder compact underwent a near full and isotropic densification process during sintering. It was observed that the nanopowders effectively suppressed the growth of micropowder grains during densification process. Conclusively, the use of nanopowder for PIM feedstock might provide a new concept for processing a full density PIM parts with fine microstructure.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.679-680
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• 2010

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.45-46
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• 2006

In recent years, micro powder injection molding $(\mu-PIM)$ is being explored as an economical fabrication method for microcomponents in microsystems technology (MST). Technical and economic comparison was performed for $\mu-PIM$ processes. Molding experiment and simulation during the filling process were performed to evaluate several different geometries and processing conditions. The influence of material parameters and process conditions on mold filling were examined as a function of features size using microchannels as an example. It was found that the heat conductivity and viscosity of feedstock, geometry and mold temperature were the most critical parameters for complete filling of micro features.

• Proceedings of the IEEK Conference
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• 2002.06a
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• pp.275-278
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• 2002

This paper proposes an efficient micro mobility scheme to support user mobility inside an access network which employs Ipv6. The proposed scheme, namely SMM(Sparse-mode Multicast for mobility), utilizes a class of multicast protocol, PIM-SM, in the visited access network to reduce signaling to the home agent as well as to the correspondent node and to minimize packet loss during the handoff when mobile user changes its point of attachment frequently. Through the simulation, the performance of the proposed SMM is analyzed and compared with those of Mobile nv6 and for the case which adpots PIM-DM. The result shows that SMM provides significantly better performance in terms of packet loss that is invariant to transmission rate and packet size.

• Design & Manufacturing
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• v.11 no.3
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• pp.1-7
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• 2017

The fabrication process of micro pattern structure with high precision and high aspect ratio using powder injection molding (PIM) is developed. In the PIM process, the metal powder is mixed with the binder systems and the mixture is injected into the metal mold. The injection molded green parts are debinded and sintered to reach final shape and properties. In this method, the optimization of physical properties such as fluidity and strength of the binder system is essential for perfect filling the high aspect ratio micro-pattern. For this purpose, the correlation between the properties of the binder system and feedstock and ${\mu}-PIM$ process was investigated, and a binder system with low viscosity at low temperature(about $110^{\circ}C$) and high strength after cooling was investigated and applied. Employing this process, high precision parts with line type micro pattern structure which has pattern size $160{\mu}m$ and aspect ratio more than 2 can be manufactured.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.60-63
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• 2009

Manufacturing technologies of micro spur gear and micro mold by micro PIM were studied with stainless steel feedstock. For molding of gears, micro mold with gear cavity of 1.2 mm in diameter was produced by wire EDM. The proper injection pressure was selected to 70bar by observation and measuring of shapes and shrinkage of gears before/after sintering. For fabrication of micro mold, a tiny polymer gear was produced by injection into the mold. Then, 316L feedstock was again injected/compressed on the polymer gear and debinded together with polymer gear followed by sintering. As a result, another metal mold with gear cavity reduced to about 20% was fabricated and through repetition of this process chain, micro gear mold with cavity about below 800 um was finally obtained. In reduction of size by injection/compression molding, height of gear tooth was shrunk more and the effort for decrease of roughness of micro cavity were carried out ultrasonic polishing and as a result, the roughness in cavity decreased from 3-4 um to about 200 nm.

• Journal of Powder Materials
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• v.9 no.4
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• pp.267-272
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• 2002

The production of micro components is one of the leading technologies in the fields of information and communiation, medical and biotechnology, and micro sensor and micro actuator system. Microfabrication (micromachining) techniques such as X-ray lithography, electroforming, micromolding and excimer laser ablation are used for the production of micro components out of silicon, polymer and a limited number of pure metals or binary alloys. However, since the first development of microfabrication technologies there have been demands for the cost-effective replication in large scale series as well as the extended range of available material. One such promising process is micro powder injection molding (PIM), which inherits the advantages of the conventional PIM technology, such as low production cost, shape complexity, applicability to many materials, applicability to many materials, and good tolerance. This paper reports on a fundamental investigation of the application of W-Cu powder to micro metal injection molding (MIM), especially in view of achieving a good filling and a safe removal of a micro mold conducted in the experiment. It is absolutely legitimate and meaningful, at the present state of the technique, to continue developing the micro MIM towards production processes for micro components.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.677-678
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• 2010

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.507-508
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• 2010