• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 2005년도 춘계학술대회 논문집
• /
• pp.278-281
• /
• 2005

Today, manufacturing capability at the micro or nano scale production field is requested strongly in view of parts and product miniaturization. Miniaturized parts and products will introduce lots of benefits in terms of high precision functionality and low energy consumption. This paper presents the results of micro milling machine tool development for micro machining process. Finite element analysis has been performed to know the relationship between design dimensional variables and structural stiffness in terms of static, dynamic, thermal aspects. Performance evaluation through machining has been tested and discussed for achievable machining characteristics.

• 대한산업공학회지
• /
• 제24권4호
• /
• pp.601-611
• /
• 1998

The machining accuracy of CNC machine tools will decrease the production lead time because the coordinate compensation of the tool path will be unnecessary to meet design specifications. Improving the accuracy of machined parts enhances the reliability and functionality of the assembly as well as the life of the product. Among various factors affecting the accuracy of machined parts, the ambient temperature is the major factor that refers to the temperature surrounding the machine and workpiece. In this study, an experiment was conducted to confirm the dimensional variations caused by changes in the ambient temperature. The ambient temperature resulted in overcutting when it increased. A developed pre-processor converts the CNC program to compensate the dimensional variations caused by temperature changes. This methodology can be used to determine the machining accuracy and improve the positioning accuracy of a machine tool.

• 한국분말재료학회지
• /
• 제10권3호
• /
• pp.151-156
• /
• 2003

In the present work some properties of nanopowders and possible areas of their applications are discussed. Main attention is paid to the use of nanodispersed powders (NDP) in new materials production technologies.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2003년도 international symposium on advanced powder metallurgy
• /
• pp.67-67
• /
• 2003

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
• /
• pp.680.2-680.2
• /
• 2006

• 산업경영시스템학회지
• /
• 제43권1호
• /
• pp.123-131
• /
• 2020

There have been a lot of studies in the past for the method of predicting the failure of a machine, and recently, a lot of researches and applications have been generated to diagnose the physical condition of the machine and the parts and to calculate the remaining life through various methods. Survival models are also used to predict plant failures based on past anomaly cycles. In particular, special machine that reflect the fluid flow and process characteristics of chemical plants are connected to hundreds or thousands of sensors, so there are not many factors that need to be considered, such as process and material data as well as application of derivative variables. In this paper, the data were preprocessed through time series anomaly detection based on unsupervised learning to predict the abnormalities of these special machine. Next, clustering results reflecting clustering-based data characteristics were applied to produce additional variables, and a learning data set was created based on the history of past facility abnormalities. Finally, the prediction methodology based on the supervised learning algorithm was applied, and the model update was confirmed to improve the accuracy of the prediction of facility failure. Through this, it is expected to improve the efficiency of facility operation by flexibly replacing the maintenance time and parts supply and demand by predicting abnormalities of machine and extracting key factors.

• 한국산업경영시스템학회:학술대회논문집
• /
• 한국산업경영시스템학회 2002년도 춘계학술대회
• /
• pp.403-412
• /
• 2002

Machine condition diagnosis is the technique to perceive the machine errors and the abrasion online without overhaul. We need the steps to predict the life span and reliability of a machine for the abrasion as with perceiving the degree of the abrasion of certain machine parts to make errors. In this study we deals with the methods to check and manage periodically and to configure the judgement criteria for the state of a machine. For the applications of CDT(Condition Diagnosis Technique) we also suggest the methods to check comparing the measured vibration values with the absolute criteria and to check the abnormality by vibration level.

• 산업경영시스템학회지
• /
• 제19권37호
• /
• pp.1-7
• /
• 1996

The grouping of parts into families and machines into cells poses an important problem for the improvement of productivity and quality in the design and planning of the flexible manufacturing system(FMS). This paper proposes a new algorithm of forming machine-part groups in case of the bottleneck machine problem and shows the numerical example. This algorithm could be applied to the large scale machine-part grouping problem.

• 한국분말재료학회지
• /
• 제16권1호
• /
• pp.9-15
• /
• 2009

Amorphization and crystallization behaviors of $Ti_{50}Cu_{50}Ni_{20}Al_{10}$ powders during high-energy ball milling and subsequent heat treatment were studied. Full amorphization obtained after milling for 30 h was confirmed by X-ray diffraction and transmission electron microscope. The morphology of powders prepared using different milling times was observed by field-emission scanning electron microscope. The powders developed a fine, layered, homogeneous structure with prolonged milling. The crystallization behavior showed that the glass transition, $T_g$, onset crystallization, $T_x$, and super cooled liquid range ${\Delta}T=T_x-T_g$ were 691,771 and 80 K, respectively. The isothermal transformation kinetics was analyzed by the John-Mehn-Avrami equation. The Avrami exponent was close to 2.5, which corresponds to the transformation process with a diffusion-controlled type at nearly constant nucleation rate. The activation energy of crystallization for the alloy in the isothermal annealing process calculated using an Arrhenius plot was 345 kJ/mol.

• 한국고분자학회:학술대회논문집
• /
• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
• /
• pp.368-368
• /
• 2006

Micro-molded parts can be defined as parts with microgram weight, parts with micro-structured surface, and parts with micro-precision. In this study, various micro-scale molded parts for various polymers were produced by using a precision micro-molding machine. Molded parts with nano-structure surface were also produced to analyze the effect of molding conditions on replication of surface pattern and higher-order structure development of molded parts. Replication of molded parts was influenced by material properties, molding conditions and size of surface pattern. Higher-order structure of molded parts was investigated by using polarized microscope. Skin-shear-core regions inside the molded parts were observed and shear region affected to surface replication.