• 산업공학
• /
• 제19권1호
• /
• pp.43-52
• /
• 2006

In order to make best use of NC machine tools with minimal labor costs, they need to be in operation 24 hours a day without being attended by human operators except for setup and tool changes. Thus, unattended machining is becoming a dream of every modern machine shop. However, without a proper mechanism for real-time monitoring of the machining processes, unattended machine could lead to a disaster. Investigated in this paper are ways to using PC camera as a real-time monitoring system for unattended NC milling operations. This study defined five machining states READY, NORMAL MACHINING, ABNORMAL MACHINING, COLLISION and END-OF-MACHINING and modeled them with DEVS (discrete event system) formalism. An image change detection algorithm has been developed to detect the table movements and a flame and smoke detection algorithm to detect unstable cutting process. Spindle on/off and cutting status could be successfully detected from the sound signals. Initial experimentation shows that the PC camera could be used as a reliable monitoring system for unattended NC machining.

• Journal of Welding and Joining
• /
• 제32권6호
• /
• pp.22-28
• /
• 2014

Most publications on friction stir welding describe phenomena or results with given process parameters like feed rate, rotation speed, angle and depth of penetration. But without a complete documentation of tool design, the results under the same process parameters are completely different. For this purpose, the Institute of Cutting and Joining Manufacturing Processes (tff), University of Kassel investigated the influence of tool roughness on the friction stir welding process. Therefore a defined surface finish was produced by turning and die sinking. As basis of comparison the constant parameters were rotation speed, feed rate, tilt angle and a heel plunge depth. Sound butt-welds were produced in aluminium alloy 6082 (AlMgSi1) with 1.5 mm sheet thickness with a turned reference tool with a surface of $Ra=0.575{\mu}m$ in position controlled mode. The surfaces are manufactured from a very fine to a very rough structure, classified by the VDI-classes with differences in the arithmetical mean roughness. It can be demonstrated with the help of temperature measures, that less heat is generated at the surfaces of the shoulder and the pin by the higher roughness due to lower active friction contact surface. This can also be seen in the resulting wormhole defects.

• 한국기계가공학회지
• /
• 제5권3호
• /
• pp.65-70
• /
• 2006

The AWJM(Abrasive Water-jet Machining) technology is one of the cutting technologies, which can cut various materials with 2 or 3 times of the speed of sound. In this study, processing conditions such as jet-pressure, cutting speed, orifice diameter and stand-off distance, are used by following the design of experiments with 3 levels. Al6061 material which is normally applied on the field, is applied. Through the S/N ratio analysis with measured values, the optimization value of processing conditions to minimize the surface roughness and taper value is obtained. The order of significance is as follows; jet pressure, cutting speed, abrasive mixing ratio, orifice diameter and stand-off distance. RSM(Response Surface Method) is applied to find the optimal processing conditions to minimize both the surface roughness and the taper value by using jet pressure, cutting speed and abrasive mixing ratio.

• 한국기계가공학회지
• /
• 제21권7호
• /
• pp.98-104
• /
• 2022

Circular sawing and milling are general machining processes used for routing fiber-reinforced plastics (FRP). In this study, the productivity and cutting quality of a circular saw and flat endmill were compared. As a result, the productivity of the circular saw was approximately ten times higher than that of the endmill for the same tool life, and the burr size of the circular saw was 14 times smaller than that of the flat-end mill. The spectrogram analysis of the cutting sound also showed that the acoustic emission of the circular saw was more uniform than that of the flat end mill. Circular sawing is thus a more suitable process for the straight cutting of pultrusion FRP than a flat endmill.

• 한국기계가공학회지
• /
• 제11권5호
• /
• pp.142-147
• /
• 2012

Machining tool conditions directly affect to quality of product and productivity of manufacturing. Many researches performed for tool condition monitoring in machining process to improve quality and productivity. Conventional methods use characteristics of signal for cutting force, motor current consumption, vibration of machine tools and machining sound. Recently, diameter of machining tool is become smaller for minimizing of mechanical parts. Tool condition monitoring using conventional methods are relatively difficult because micro machining using small diameter tool has low machining load and high cutting speed. These days, the direct monitoring for tool conditions using vision system is performed actively. But, vision system is affected by external conditions such as back ground of image and illumination. In this study, minimizing technology of external conditions using distribution analysis of image data are developed in micro machining using small diameter drill and tap. The image data is gathered from vision system. Several sets of experiment results are performed to verify the characteristics of the proposed machining technology.

• 반도체디스플레이기술학회지
• /
• 제16권3호
• /
• pp.20-24
• /
• 2017

For process improvement and cutting down on expenses in solar cell industry, it is necessary to improve recycling process of wafer manufacturing. In this research, a study is introduced to develop classifier which is for recycling of abrasive. First of all, recycling process of wafer manufacturing is analyzed. And then, 3 steps of experiments such as oil removal, impurities removal and classification were executed. For the classification of slurry, a classifier is designed and manufactured. From experiments, it is verified that ultra sound vibration and flux are very important factors for classification. By experiencing the recycling processes and making devices, the technique can be initiated industry if needed such as decreasing waste and cutting down on expenses.

• Journal of Welding and Joining
• /
• 제32권5호
• /
• pp.50-57
• /
• 2014

Friction Stir Welding (FSW) is a complex process with several mutually interdependent parameters. A slight difference from known settings may lead to imperfections in the stirred zone. These inhomogeneities affect on the mechanical properties of the FSWed joints. In order to prevent the failure of the welded joint it is necessary to detect the most critical defects non-destructive. Especially critical defects are wormhole and lack of penetration (LOP), because of the difficulty of detection. Online thermography is used process-accompanying for defect detecting. A thermographic camera with a fixed position relating to the welding tool measures the heating-up and the cool down of the welding process. Lap joints with sound weld seam surfaces are manufactured and monitored. Different methods of evaluation of heat distribution and intensity profiles are introduced. It can be demonstrated, that it is possible to detect wormhole and lack of penetration as well as surface defects by analyzing the welding and the cooling process of friction stir welding by passive online thermography measurement. Effects of these defects on mechanical properties are shown by tensile testing.

• 터널과지하공간
• /
• 제10권4호
• /
• pp.516-525
• /
• 2000

최근, 도시 재개발과 산업설비 개·보수에 따른 노후화된 콘크리트 및 철근구조물에 대하여 환경 공해가 발생하지 않는 해체 기술 개발에 대한 요구가 급증하고 있다. 본 연구는 철근 구조물의 폭발절단 해체를 위한 성형폭약을 개발하기 위하여 폭발절단 효과에 영향을 주는 요소인 대상 구조물의 재질 및 형상, 두께와 강도 특성, 성형폭약의 형상, 폭약의 종류, 장약량, liner의 종류, stand-off distance, 성형폭약의 폭 및 너비, 기폭방법에 따른 영향과 폭발 절단시 발생되는 폭풍압에 의한 진동 및 소음의 영향 등을 검토함으로 폭발절단 최적조건을 선정하였다. 따라서, 본 연구를 통해 얻어진 폭발절단기술은 강교, 공장, 폐선박 등의 해체에도 적용될 것이다.

• International Journal of Internet, Broadcasting and Communication
• /
• 제13권2호
• /
• pp.1-6
• /
• 2021

For competitive hotel business, the hotel must have a sound prediction capability to balance the demand and supply of hospitality products. To have a sound prediction capability in the hotel, it should be prepared to be equipped with a new technology such as quantum computing. The quantum computing is a brand new cutting-edge technology. It will change hotel business and even the whole world too. Therefore, we study the impact of quantum computing on supply chain management (SCM) and hotel performance. Toward the goal we have developed the research model including six constructs: quantum (computing) prediction, communication, supplier relationship, service quality, non-financial performance, and financial performance. The result of the study shows a significant influence of quantum (computing) prediction on hotel performance through the mediating role of SCM in the hotel. Quantum prediction is highly significant in enhancing the SCM in the hotel. However, the direct effect between the quantum prediction and hotel performance is not significant. The finding indicates that hotels which would install the quantum computing technology and utilize the quantum prediction could hugely benefit from the performance improvement.

• 한국환경과학회지
• /
• 제16권7호
• /
• pp.771-778
• /
• 2007

This study has been conducted to achieve the following objectives: First, in order to understand the horizontal propagation and attenuation characteristics for the railroad traffic noise, we selected areas within 100 meters away from the railroad and then selected Saemaul-ho and Mugoongwha-ho as the subjects for our experiment. In this way, we analyzed the horizontal propagation and attenuation characteristics for the traffic noise occurring in diversified areas. Second, in order to understand the vertical propagation and attenuation characteristics for the railroad traffic noise, we measured and analyzed the distributional characteristics of vertical sound pressure levels on each floor of multi-storied apartment buildings according to changes of traffic load and types, and the existence or nonexistence of soundproof walls. For the case of the railroad traffic noise, we also selected Samaul-ho and Mugoongwha-ho as the subjects for our experiment, and we measured and analyzed the different noise levels on each floor of multi-storied apartment buildings from the soundproof wall. The results of Horizontal propagation and attenuation characteristics for the railroad traffic noise are as follows: In cases of the flat land, cutting land, and bridge area, as distance increases, the sound pressure level steadily decreases. The sound pressure level for the bridge area is higher than that of the flat land with a measurement of $5.5{\sim}10.2\;dB(A)$. Vertical propagation and attenuation characteristics for the railroad traffic noise are as follows: The amount of sound pressure level decrease is $14.2{\sim}14.8\;dB(A)$ for Samaul-ho and $13.5{\sim}14.3\;dB(A)$ for Mugoongwha-ho when measuring the vertical sound pressure levels at heights lower than 4.5 m, which indicates a fairly large decrease. At 6 m, the amount of decrease is 8.6 dB(A) for Samaul-ho and 8.2 dB(A) for Mugoongwha-ho, which indicates a small decrease.