• 한국정밀공학회지
• /
• 제29권12호
• /
• pp.1279-1284
• /
• 2012

Micro structures which are widely used at various fields are commonly fabricated by lithograph, etching and laser methods. Recently, with the emergence of micro tools and ultra-precision machine tools, fabrication of the micro structures obtained using end-milling are studied. However, there are some problems due to the diameter of the micro end-mill getting smaller below $100{\mu}m$. The micro run-out resulted from miniaturization of end-mills have influence seriously on accuracy of micro structures. The error of run-out with a tooling jig showed a decrease of about $9.3{\mu}m$. Furthermore, micro structures with width of $30{\mu}m$ could be applied through experiments of slot machining obtained using 30 and $50{\mu}m$ end-mill. Also, narrow angle structures with $30^{\circ}$ angle could be applied through analysis of machining acute angle structures. Based on basic experiments, micro fluidics channels and spiral patterns for air bearing were machined.

• 한국정밀공학회지
• /
• 제18권7호
• /
• pp.174-178
• /
• 2001

In order to reduce the lead-time and cost, recently the technology of rapid protoyping and manufacturing(RPM)has been widely used. Machining process is still considered as one of the effective RPM methods that have been developed and currently available in the industry. It also offers practical advantages such as precision and versatility. Some considerations are still required during the machining process. One of the most important points is fixturing. There should be an effective method of fixturing since the fixturing time depends on the complexity of geometry of the part to be machined. In this paper, the rapid manufacturing process has been developed combining machining with automatic filling. The proposed fixturing technique using automatic filling can be widely applicable to free surface type of product such as a fan. In the filling stage, remeltable material is chosen for the filling process. An automatic set-up device attachable to the table of the machine has also been developed. The device ensures the quality during a series of machining operations. This proposed process has shown to be a useful method to manufacture the required products with the reduced the response-time and cost.

• 한국정보과학회논문지:소프트웨어및응용
• /
• 제31권9호
• /
• pp.1204-1217
• /
• 2004

기존의 통계적인 기법과 기계학습 기법 등을 이용한 자동 문서 분류는 주로 문서 벡터만으로 분류기를 학습하여 분류를 행하기 때문에 특정 범주로 문서를 분류하는데 명확치 않은 경우가 빈번히 발생하여 일정 수준 이상의 정확도를 얻는 데에는 한계를 보이고 있다. 이러한 문제를 해결하기 위해 본 논문에서는 기존 문서 분류 알고리즘에 범주 간의 관련성을 반영하여 분류를 시행하는 방법을 제안한다. 이 방법은 간단한 알고리즘에 비해 좋은 성능을 보이고 있는 k-NN 분류 알고리즘을 이용하여 일차적인 문서 분류를 수행한 후 특정 범주로 분류하기가 명확치 않을 경우, 객체 기반 시소러스에서 제공되는 범주들 간의 일반화 관계, 집성화 관계, 연관화 관계 그리고 인스턴스 관계를 이용하여 문서가 할당될 범주를 결정함으로써 자동 문서 분류의 정확도를 향상시킬 수 있다. 본 논문에서 제안된 방법으로 실험한 결과 k-NN 분류 알고리즘의 분류 결과에 비해 재현율은 유지되면서 최고 13.86% 까지 정확률이 향상되었다.

• 한국정밀공학회지
• /
• 제28권6호
• /
• pp.701-708
• /
• 2011

Although Titanium material has superior properties, it belongs to difficult-to-machine materials. The present research applies magnetic abrasive finishing to precision machining of internal-face of titanium pipes, and analyzed & assessed the influence of grinding conditions on magnetic abrasive effects through the removed amount and surface roughness of materials. There was the influence on grinding properties according to change of rotational speed, a total input of mixed powder and an input of grinding liquid, and when the total input, rotational speed and ratio of electrolytic iron versus magnetic abrasives are 8g and 1000rpm, it was most advantageous in aspects of surface roughness and material removal amount, and the grinding liquid remarkably improved the surface roughness and material removal amount only with addition of trace amounts of light oil rather than dry machining conditions. And a result of considering the influence on grinding properties by using an inert gas (Argon gas) for improving grinding properties of the internal-face of titanium pipe, the present research has obtained improvement effects in the removal amount and surface roughness through utilization of an inert gas.

• 한국정밀공학회지
• /
• 제26권6호
• /
• pp.131-135
• /
• 2009

In this study, we performed the compressive strength test of trabecular bone in knee joint for measuring the elastic modulus and ultimate strength. The main knee joint is femorotibial articulation between the lateral and medial femorotibial condyle. In the case of osteoarthritis, some patients have only medial condylar osteoarthritis. We performed the mechanical test for comparison the difference of the each condylar strength. We used diamond core-drill and linear precision saw for making the specimens. Specimens were cored from both condyle in distal femur and proximal tibia in fresh cadaver (male 10, female 12), and tested by universal test machine with temperature control saline circulation system. Results of the test in distal femoral parts, averaged elastic modulus was $360.61{\pm}159.40MPa$ for male, $150.89{\pm}70.65MPa$ for female. Averaged ultimate strength was $6.79{\pm}2.91MPa$ for male, $2.89{\pm}1.31MPa$ for female. Male was 2.4 times stronger than female. In the proximal tibial parts, averaged elastic modulus was $108.80{\pm}52.88MPa$ for male, $73.45{\pm}55.06MPa$ for female. Averaged ultimate strength was $2.59{\pm}1.39MPa$ for male, $1.75{\pm}1.16MPa$ for female. Male was 1.5 times stronger than female. In the distal femoral condyle, medial condyle had more strength than lateral condyle at middle region. But lateral condyle had more strength than medial condyle at anterior & posterior regions (p<0.02). In the proximal tibial condyle, medial condyle had more strength than lateral condyle. (p<0.01).

• 한국정밀공학회지
• /
• 제27권3호
• /
• pp.135-141
• /
• 2010

Researchers continue to explore possibilities for expanding additive manufacturing (AM) technologies into direct product manufacturing. One limitation is in the materials available for use in AM that can meet the needs of end-use applications. Stereolithography (SL) is an AM technology well known for its precision and high quality surface finish capabilities. SL builds parts by selectively crosslinking or solidifying photo-curable liquid resins, and the resin industry has been continuously developing new resins with improved performance characteristics. This paper introduces a unique SL machine that can fabricate parts out of multiple SL materials. The technology is based on using multiple vats positioned on a rotating vat carousel that contain different photo-curable materials. To change the material during the process, the build platform is raised out of the current vat, a new vat with a different material is rotated under the platform, and the platform is submerged into the new vat so that the new material can be used. This paper introduces a new vat exchange mechanism, cleaning process, recoating process, resin leveling mechanism and process planning technologies for the implementation of multiple material SL. An overview of the system framework is provided and the system integration and control software is described. In addition, several multiple material test parts are designed, fabricated, and described.

• 소성∙가공
• /
• 제17권2호
• /
• pp.124-129
• /
• 2008

Net shape forging technologies give many effects into the costs and qualities for the finished products. So, the studies to reduce the additional machining amount are very important in forging industry. Specially, there are two main topics in cold forging industry, such as, tool life and precision forging. In this study, new forging technique was proposed to eliminate the machining process for fixing up the length and improve the lead accuracy of gear. The luck-up hub is manufactured through many processes, such as upsetting, piercing and direct extrusion. The gear is formed in direct extrusion process; however, lead accuracy of the gear is over allowance limit. Therefore, the additional sizing process must be added. In this study, process design for closed-die forging of a lock-up hub used for a component of automobile transmission was made using three-dimensional finite element simulations, and the strain distributions and velocity distributions are investigated through the post processor. The rigid-plastic finite-element method for back pressure forging has been used in order to reduce development time and die cost. Using the FEM simulation, we found the optimum value of back pressure. The prototypes of lock-up hub parts were forged into the net-shape. In the experiment, lead precision of tooth are measured by the CCMM(Contact Coordinate Measuring Machine). The dimensional accuracy of forged part was improved up to the 40% when back press was applied.

• International Journal of Precision Engineering and Manufacturing
• /
• 제8권2호
• /
• pp.38-43
• /
• 2007

This paper describes ultrasonically assisted grinding used to obtain a glossy surface quickly and precisely. High-quality surfaces are required for plastic injection molding dies used in the production of plastic parts such as dials for cellular phones. Traditionally, in order to finish the dies, manual polishing by a skilled worker has been required after the machining processes, such as electro discharge machining (EDM), which leaves an affected layer, and milling, which leaves tooling marks. However, manual polishing causes detrimental geometrical deviations of the die and consumes several days to finish a die surface. Therefore, a machining process for finishing dies without manual polishing to improve the surface roughness and form accuracy would be extremely valuable. In this study, a 3D positioning machine equipped with an ultrasonic spindle was used to conduct grinding experiments. An electroplated diamond tool was used for these experiments. Generally, diamond tools cannot grind steel because of excessive wear as a result of carbon atoms diffusing into bulk steel and chips. However, ultrasonically assisted grinding can achieve a fine surface (roughness Rz of $0.4{\mu}m$) on die steel without severe tool wear. The final aim of this study is to realize mirror surface grinding for injection molding dies without manual polishing. To do this, it is necessary to fabricate an electroplated diamond tool with high form accuracy and low run-out. This paper describes a tool-making method for high precision grinding and the grinding performance of a self-electroplated tool. The ground surface textures, tool performance and tool life were investigated A ground surface roughness Rz of 0.14 um was achieved Our results show that the spindle speed, feed rate and cross feed affected the surface texture. One tool could finish $5000mm^2$ of die steel surface without any deterioration of the ground surface roughness.

• Genomics & Informatics
• /
• 제14권2호
• /
• pp.53-61
• /
• 2016

Toxoplasma gondii is an intracellular Apicomplexan parasite and a causative agent of toxoplasmosis in human. It causes encephalitis, uveitis, chorioretinitis, and congenital infection. T. gondii invades the host cell by forming a moving junction (MJ) complex. This complex formation is initiated by intermolecular interactions between the two secretory parasitic proteins-namely, apical membrane antigen 1 (AMA1) and rhoptry neck protein 2 (RON2) and is critically essential for the host invasion process. By this study, we propose two potential leads, NSC95522 and NSC179676 that can efficiently target the AMA1 hydrophobic cleft, which is a hotspot for targeting MJ complex formation. The proposed leads are the result of an exhaustive conformational search-based virtual screen with multilevel precision scoring of the docking affinities. These two compounds surpassed all the precision levels of docking and also the stringent post docking and cumulative molecular dynamics evaluations. Moreover, the backbone flexibility of hotspot residues in the hydrophobic cleft, which has been previously reported to be essential for accommodative binding of RON2 to AMA1, was also highly perturbed by these compounds. Furthermore, binding free energy calculations of these two compounds also revealed a significant affinity to AMA1. Machine learning approaches also predicted these two compounds to possess more relevant activities. Hence, these two leads, NSC95522 and NSC179676, may prove to be potential inhibitors targeting AMA1-RON2 complex formation towards combating toxoplasmosis.

• 한국산업융합학회 논문집
• /
• 제23권4_2호
• /
• pp.675-682
• /
• 2020

Multi-wire sawing is the prominent technology employed to cut hard material ingots into wafers. This paper aimed to research the effect of diamond toughness index on the cutting performance of electroplated diamond wire. Three different toughness index of diamond abrasives were used to manufacture electroplated diamond wires. The cutting performance of electroplated diamond wire is verified through experiments, in which sapphire ingot are cut using single wire sawing machine. A single wire saw for constant load slicing is developed for the cutting performance evaluation of electroplated diamond wire. Choosing the cutting depth, total cutting depth, cutting force and wear of electroplated diamond wires as evaluation parameters, the performance of electroplated diamond wire is evaluated. The results of this study showed that there was a significant direct relationship between the toughness index of diamond abrasives and the cutting performance. Results demonstrated that diamond abrasive with a high toughness index showed higher cutting performance. However, all diamond abrasives showed similar cutting performance under low load conditions. The results of this paper are useful for the development of cutting large diameter ingots and cutting high hardness ingots at high speed.