• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.871-874
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• 2004

Fabrication of a high-resolution shadow mask, or called nanostencil, is presented. This high-resolution shadowmask is fabricated by a combination of MEMS processes and focused ion beam (FIB) milling. 500 nm thick and 2x2 mm large membranes are made on a silicon wafer by micro-fabrication processes of LPCVD, photolithography, ICP etching and bulk silicon etching. Subsequent FIB milling enabled local membrane thinning and aperture making into the thinned silicon nitride membrane. Due to high resolution of FIB milling process, nanoscale apertures down to 70 nm could be made into the membrane.

• Journal of Powder Materials
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• v.6 no.1
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• pp.88-95
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• 1999

The purpose of this study is to investigate the manufacturing feasibility of WC-Co milling inserts via Powder Injection Molding (PIM) process. WC-Co is used in a wide variety of cutting tools due to its high hardness, stiffness, compressive strength and wear resistance properties. WC-Co parts for a high stress application were conventionally produced by the press and sinter method, which were Iimited to 2 dimensional shapes. Manufacturing WC-Co parts for a high stress application by PIM implies that tool efficiency can be highly improved due to increased freedom is design. P30 grade WC powder (WC-Co-TiC-TaC system) was mixed with RIST-5B133 binder and injection molded into milling inserts (Taegu Tech. Model WCMX 06T 308). The mean grain size of the powder was about 0.8$\mu$m. Injection molded specimens were debound by solvent extraction and thermal degradation method at various conditions. The specimens were sintered at 140$0^{\circ}C$ for 1 hr in vacuum. Carbon content, weight loss, dimensional change, and macro defects of the specimen were carefully monitored at each stage of the PIM process. PIMed WC-Co milling inserts reached 100% full density after sinteing. Its mechanical properties and micro-structures were comparable with the press and sintered milling insert. Carbon content of the sintered WC-Co insert was mainly determained by the atmosphere of thermal debinding. By controlling powder loading and injection molding condition, dimensional accuracy could be obtained within 0.4%. We confirm that PIM can not only be an alternative manufacturing method for WC-Co parts economically but also provide a design freedom for more effieient cutting tools.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.199-202
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• 2005

High speed milling process is emerging as an important fabrication process benefits include the ability to fabricate micro and meso-scale parts out of a greater range of materials and with more varied geometry. It also enables the creation of micro and meso-scale molds for injection molding. Factors affecting surface roughness have not been studied in depth for this process. A series of experiments has been conducted in order to begin to characterize the factors affecting surface roughness and determine the range of attainable surface roughness values for the high speed milling process. It has previously been shown that run-out creates a greater problem for the dimensional accuracy of parts created by high speed milling process. And run-out also has a more significant effect on the surface quality of milled parts. The surface roughness traces reveal large peak to valley variations. This run-out is generated by spindle dynamics and tool geometry. In order to investigate the relationship between tool setting errors and surface roughness end tilted mills were used to cut aluminum samples. The results indicate that tool setting errors have significant effects on surface roughness and cutting forces.

• Korean Journal of Materials Research
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• v.31 no.12
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• pp.677-681
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• 2021

The Mn-Zn ferrite powders were prepared by high energy ball milling, then compacted and sintered at various temperatures to assess their sintering behavior and magnetic properties. The initial ferrite powders were spherical in shape with the size of approximately 70 ㎛. After 3 h of ball milling at 300 rpm, aggregated powders ~230 nm in size and composed of ~15 nm nanoparticles were formed. The milled powders had a density of ~70 % when compacted at 490 MPa for 3 min. In the samples subsequently sintered at 1,273 K ~ 1,673 K for 3 h, the MnZnFe₂O₄ phase was detected. The density of the sintered samples had a tendency to increase with increasing sintering temperature up to 1,473 K, which produced the highest density of 98 %. On the other hand, the sample sintered at 1,373 K had the highest micro-hardness of approximately 610 Hv, which is due to much finer grains.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.38-42
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• 2002

In the recent, electro-rheological fluid has been used for micro polishing of the 3-dimensional micro-aspherical lens and some sectional parts with defects on the wide flat wafer. The ER fluid has the properties that its viscosity has drastic changed under some electric fields. Therefore, ER fluid can be applicable to the micro polishing fur some parts using these properties. In this paper, the experimental device has been constructed using the precision milling machine in order to micro polishing far some sectional parts of a 4 inches wafer It is consisted of a small steel electrode, a wafer fixture, DC10mA and 5KV power supply unit, and a controller unit. Using the ER experimental device, possibility of amending for wide flat wafer and micro polishing of some micro part has been analyzed.

• Transactions of Materials Processing
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• v.15 no.9 s.90
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• pp.673-678
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• 2006

Demands for micro parts have increased with recent advances in IT and machinery industries. However, the present technology loaves much to be desired to effectively produce parts with the volume of $1mm^{3}$ and less by mechanical method in large quantities. This paper provides a method for efficient quantity production of complete micro 3D structure using micro end-milling cutting process. The possibility has proven via manufacturing experiment of a multistage micro complex gear structure of $500{\mu}m$ in length, $500{\mu}m$ in maximum external diameter and a volume of $1mm^{3}$ and less.

• Korean Journal of Food Science and Technology
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• v.20 no.4
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• pp.504-510
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• 1988

The physicochemical properties of rice flours which were obtained by dry milling(blade, hammer, test and micro mill) and wet & dry milling (roller & micro mill) were investigated. The resulting flour particle sizes were reduced in the order that of blade, hammer, test, micro and roller & micro mill. Scanning electron microscopic examination showed that the starch granules were freed from the imbedding matrix as the particles became finer. The test-milled flour had the hightest levels of starch damage, maltose value and hot-water soluble amylose content, and the blade-milled flour showed the lowest levels. Amylograph viscosity and gelatinization temperature of the flours decreased as the particles became finer, and the addition of $Hg^{+2}$ increased the peak viscosity of the dry-milled flour pastes, whereas the wet & dry-milled flour did not show any changes. The blue values and ${\lambda}$max values of the iodine complex of the cold-water extractable ${\alpha}-D-glucan$ from flours were in the range of 0.023-0.029 and 518-522nm, respectively, indicating these materials were shown to be mainly composed of amylopectin-like polymer.

• Design & Manufacturing
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• v.17 no.2
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• pp.22-26
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• 2023

As Light-Emitting Diodes(LEDs) continue to advance in performance, their application in automotive lamps is increasing. Automotive LEDs utilize light guides not only for aesthetics but also to control light quantity and direction. Light guides employ patterns of a few hundred micrometers(㎛) to regulate the light, and the surface roughness(Ra) of these patterns can reach tens of nanometers(nm). Given that these light guides are produced through injection molding, mold processing technology with high surface quality micro-patterns is required. This study serves as a preliminary investigation into the development of high surface quality micro-pattern processing technology. It examines the surface roughness of the workpiece based on the cutting direction of the pattern and the cutting fluid type when cutting micro-patterns on STAVAX steel using cubic Boron Nitride(cBN) tools. The experiments involved machining a step-shaped micro-pattern with a height of 60 ㎛ and a pitch of 400 ㎛ in a 22×22 mm area under identical cutting conditions, with only the cutting direction and cutting fluid type being varied. The machining results of four cases were compared, encompassing two cases of cutting direction(parallel to the pattern, orthogonal to the pattern) and two cases of cutting fluid type (flood, mist). Consequently, the Ra value was found to be the highest(Ra 128.33 nm) when machining with the flood type in parallel to the pattern, while it was the lowest(Ra 95.22 nm) when machining with the mist type orthogonal to the pattern. These findings confirm that there is a difference of up to 25.8 % in the Ra value depending on the cutting direction and cutting fluid type.

• Journal of Powder Materials
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• v.17 no.4
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• pp.302-311
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• 2010

In this research, the refinement behavior of the coarse magnesium powders fabricated by gas atomization was investigated as a function of milling time using a short duration high-energy ball milling equipment, which produces fine powders by means of an ultra high-energy within a short duration. The microstructure, hardness, and formability of the powders were investigated as a function of milling time using X-ray diffraction, scanning electron microscopy, Vickers micro-hardness tester and magnetic pulsed compaction. The particle morphology of Mg powders changed from spherical particles of feed metals to irregular oval particles, then platetype particles, with increasing milling time. Due to having HCP structure, deformation occurs due to the existence of the easily breakable C-axis perpendicular to the base, resulting in producing plate-type powders. With increasing milling time, the particle size increased until 5 minutes, then decreased gradually reaching a uniform size of about 50 micrometer after 20 minutes. The relative density of the initial power was 98% before milling, and mechanically milled powder was 92~94% with increase milling time (1~5 min) then it increased to 99% after milling for 20 minutes because of the change in particle shapes.

• Laser Solutions
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• v.17 no.3
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• pp.10-14
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• 2014

By the specific character of femtosecond laser controlled volume of magnitude of micrometer scale could be ablated without melting phase in SKD11 and SUS304. According to the laser machining parameters various sectional shapes could be engraved on the surface of metals. Typical engraved lines were $10{\mu}m$ wide and deep. Coarse-milled surface was made $10{\mu}m$ lower than the original elevation by a bunch of laser-engraved lines in suitable spacing. The repeated banks with a height of $10{\mu}m$ could be made with the combination of the intact area.