• International Journal of Precision Engineering and Manufacturing
• /
• 제4권3호
• /
• pp.48-54
• /
• 2003

This paper deals with mirror grinding of a small-sized aspherical lens by a resin bonded diamond spherical wheel. Up to now, a spherical lens has been used for the lens of the optical communication optical part. However, recently, aspherical optical parts are mainly used in order to attempt the improvement in image quality and miniaturization of the optical device. It is possible to manufacture the aspherical lens which is presently being used in optical instrument through ultra-precision machining technology. Also, to realize compactness, efforts are being made to produce a micro aspherical lens, fur which the development of a high-precision, micro molding die is inevitable. Therefore, extensive research is being done on methods of producing a micro aspherical surface by high-precision grinding. In this paper, the spherical wheel was trued by cup-shaped truer and tool path was calculated by the radius of curvature of the wheel after truing and dressing. Then in the aspherical grinding experiment, WC material which is used as a melding die for the small-sized aspherical lens was ground. The results showed that a form accuracy of 0.1918 $\mu\textrm{m}$ P-V and a surface roughness of 0.064 $\mu\textrm{m}$ Rmax could be achieved.

• 한국정밀공학회지
• /
• 제18권12호
• /
• pp.82-87
• /
• 2001

This paper deals with mirror grinding of a small-sized aspherical lens by the resin bonded diamond spherical wheel. Up to now, a spherical lens has been used for the lens of the optical communication optical part. However, recently, the aspherical optical parts are mainly used in order to attempt the improvement in image quality and miniaturization of the optical device. It is possible to manufacture the aspherical lens which is presently being used in optical instrument through ultra-precision machinery technology. Also, to realize compactability, efforts are being made to produce a micro aspherical lens, for which the development of a high-precision, micro molding die is inevitable. Therefore, extensive research is being done on methods of producing an micro aspherical surface by high-precision grinding. In this paper, the spherical wheel was trued by cup-type truer and tool path was calculated by the radius of curvature of wheel after truing and dressing. And then in the aspherical grinding experiment, WC material which is used as a molding die for the small-sized aspherical lens was ground. It results was that a form accuracy of 0.1918${\mu}m$ P-V and a surface roughness of 0.064${\mu}m$ Rmax.

• 한국정밀공학회지
• /
• 제28권12호
• /
• pp.1347-1352
• /
• 2011

Recently, as the aged population grows around the world, many medical instruments, devices, and their fabrication processes are developing. Among the devices, a drug delivery stent is a good example for precision machining. Conventional drug delivery stent has problem of the remaining polymer because the drug is coated on the surface with it. If the drug is impregnated into the micro hole array on the stent surface, the polymer can be perfectly eliminated. Micro sized holes are generally fabricated by laser machining however, the fabricated holes do not have an enough aspect ratio to contain the drug or a good surface finish to deliver the stend to blood vessel tissue. To overcome these problems, we propose a vibration-assisted machining mechanism with PZT (Piezoelectric Transducers) for abrication of micro sized holes better. The results indicated that the burr size can be significantly decreased with vibration assisted in nanosecond pulse laser drilling test.

• Composites Research
• /
• 제32권3호
• /
• pp.141-147
• /
• 2019

In this study, micro-sized and nano-sized pure aluminum (Al) powders were compressed by unidirectional pressure at room temperature. Although neither type of Al bulk was heated, they had a high relative density and improved mechanical properties. The microstructural analysis showed a difference in the process of densification according to particle size, and the mechanical properties were measured by the Vickers hardness test and the nano indentation test. The Vickers hardness of micro Al and nano Al fabricated in this study was five to eight times that of ordinary Al. The grain refinement effect was considered to be one of the strengthening factors, and the Hall-Petch equation was introduced to analyze the improved hardness caused by grain size reduction. In addition, the effect of particle size and dispersion of aluminum oxide in the bulk were additionally considered. Based on these results, the present study facilitates the examination of the effect of particle size on the mechanical properties of compacted bulk fabricated by the powder metallurgy method and suggests the possible way to improve the mechanical properties of nano-crystalline powders.

• International Journal of Fuzzy Logic and Intelligent Systems
• /
• 제4권3호
• /
• pp.316-321
• /
• 2004

In this paper, we have developed a new mounting head system for flip chip. The proposed head system consists of a macro/micro positioning actuator for stable force control. The macro actuator provides the system with a gross motion while the micro device yields fine tuned motion to reduce the harmful impact force that occurs between very small sized electronic parts and the surface of a PCB(printed circuit board). In order to show the effectiveness of the proposed macro/micro chip mounting system, we compared the proposed system with the conventional chip mounting head equipped with a macro actuator only. A series of experiments were executed under the mounting conditions such as various access velocities and PCB stiffness. As a result of this study, a satisfactory voice coil actuator as the micro actuator has been developed, and its performance meet well the specifications desired for the design of the chip mounting head system and show good correspondence between theoretical analysis and experimental results.

• 한국기계가공학회지
• /
• 제13권4호
• /
• pp.21-27
• /
• 2014

The injection molding process has several advantages enabling it to produce large quantities of molded plastic products using a repetitive process. In recent years, it has been necessary to develop an injection molding process with micro/nano-sized patterns for application to the semiconductor industry and to the bio/nano manufacturing industry. In this study, we apply gas pressure to the inside of a mold and consider the gas dissolution phenomenon for a resin filling into a micro pattern with a line structure. Using numerical analysis, we calculate the filling ratio with respect to time for various internal gas pressures and various aspect ratios of the micro-patterns.

• Journal of Ginseng Research
• /
• 제42권3호
• /
• pp.361-369
• /
• 2018

Ginsenosides, dammarane-type triterpene saponins obtained from ginseng, have been used as a natural medicine for many years in the Orient due to their various pharmacological activities. However, the therapeutic potential of ginsenosides has been largely limited by the low bioavailability of the natural products caused mainly by low aqueous solubility, poor biomembrane permeability, instability in the gastrointestinal tract, and extensive metabolism in the body. To enhance the bioavailability of ginsenosides, diverse micro-/nano-sized delivery systems such as emulsions, polymeric particles, and vesicular systems have been investigated. The delivery systems improved the bioavailability of ginsenosides by enhancing solubility, permeability, and stability of the natural products. This mini-review aims to provide comprehensive information on the micro-/nano-sized delivery systems for increasing the bioavailability of ginsenosides, which may be helpful for designing better delivery systems to maximize the versatile therapeutic potential of ginsenosides.

• 한국가스학회지
• /
• 제19권5호
• /
• pp.75-80
• /
• 2015

나노 및 마이크로 크기의 알루미늄(Al) 분진은 매우 높은 연소열을 가지고 있어서 로켓 추진체와 폭발물 등을 제조하는 원료로 많이 사용되고 있다. 본 연구에서는 서로 다른 크기의 입자경 (70 nm, 100 nm, $6{\mu}m$, $15{\mu}m$)을 가진 알루미늄 분진을 사용하여 열분해 위험성을 실험적으로 검토하였다. 이를 위해 열중량분석장치(TGA)를 사용하여 승온속도의 변화에 따른 열분해특성을 조사하고 입경이 다른 나노 및 마이크로 크기의 Al에서의 중량개시온도(Temperature of weight gain)로부터 발화온도를 추정하였다. 승온속도가 동일한 조건에서 Al분진의 중량개시온도는 입경이 증가할수록 또한 공기중 승온속도가 증가할수록 증가하는 경향을 나타냈다. 이러한 실험결과로부터 Al분진의 열분해 위험성은 분진 입자경의 증가와 함께 감소할 것으로 추정되었다.

• 한국정밀공학회지
• /
• 제31권5호
• /
• pp.381-387
• /
• 2014

This paper introduces a system to machine micro-sized patterns effectively on surface based on micro-milling process using tools with simultaneous rotation and oscillation, oscillation micro milling. To review the effectiveness of proposed concept, we integrated a micro-spindle supported by active magnetic bearings with a precision 3-axis air bearing stage using double-wedge mechanism, and tested this oscillation milling. Two types of oscillation milling were tested, which are linear oscillation milling with a flat end mill and elliptical oscillation milling with a ball end mill with 0.3 mm of diameter. The spindle was rotating 110 krpm and workpiece was moving constant speed of 2~8 mm/sec during the oscillation milling. As the results, multiple oval shape dimples were generated in regular spacing, and the variation of elliptical motion made different shapes of patterns. The results showed that proposed oscillation milling can be successfully used for machining repeated micro-patterns.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2003년도 춘계학술대회 논문집
• /
• pp.656-659
• /
• 2003

Although Hereafter a mass production will claim for patterning nano sized thickness or line in micro-nano industry. existent lithography fabrication has many usable fields, it has complex fabrication steps, expensive values and row work rates. Development of Dip-pen type nano plotter using polymer actuator can construct row cost mass production system because it will change existent lithography fabrication more simple and easy.