• 한국생산제조학회지
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• 제23권3호
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• pp.250-258
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• 2014

Due to recent industrial growth and development, there has been a high demand for light and highly durable materials. Therefore, a variety of new materials has been developed. These new materials include carbon fiber reinforced plastic (CFRP or CRP), which is a wear-, fatigue-, heat-, and corrosion-resistant material. Because of its advantageous properties, CFRP is widely used in diverse fields including sporting goods, electronic parts, and medical supplies, as well as aerospace, automobile, and ship materials. However, this new material has several problems, such as delamination around the inlet and outlet holes at drilling, fiber separation, and tearing on the drilled surface. Moreover, drill chips having a fine particulate shape are harmful to the work environment and engineers' health. In fact, they deeply penetrate into machine tools, causing the reduction of lifespan and performance degradation. In this study, CFRP woven and unidirectional prepregs were formed at $45^{\circ}$ and $90^{\circ}$, respectively, in terms of orientation angle. Using a high-speed steel drill and a TiAIN-coated drill, the two materials were tested in three categories: cutting force with respect to RPM and feed speed; shape changes around the input and outlet holes; and the shape of drill chips.

• 한국터널지하공간학회 논문집
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• 제17권6호
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• pp.605-614
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• 2015

주방식 지하구조물은 여러 개의 암주의 룸으로 구성된 격자 형태의 구조물로 굴착순서에 따라 주방식 지하구조물의 시공성과 경제성이 좌우될 수 있다. 본 연구에서는 주방식 지하구조물의 굴착공정에서 중요하게 다뤄질 수 있는 발파굴착 공정을 장비 운영과 현행 발파 규정 및 건설공사 표준품셈에 근거하여 검토하였다. 굴착공법으로는 점보드릴을 이용한 발파공법을 가정하였으며, 기존연구에서 제시한 가로 세로 순차시공방식으로 검토하였다. 주방식 지하구조의 계획부지 크기에 따라 굴착공기와 장비운영 등을 고려하여 전체 굴착공정을 예상할 수 있었으며 막장운영 계획에 따라 운영가능한 장비수를 고려하여 전체 굴착공기를 예상할 수 있었다.

• 한국진공학회지
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• 제18권5호
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• pp.337-345
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• 2009

패키지 기판의 지름 $100{\mu}m$ 이하 미세 드릴 구멍의 경우 습식 디스미어 공정만으로는 구멍 내부의 스미어를 효과적으로 제거할 수 없다. 본 연구에서는 습식 디스미어 공정의 이전 단계에서 대기압 플라즈마를 처리하여 소수성의 기판 표면을 친수성으로 개질하고자 하였다. 대기압 플라즈마 공정은 리모트 DBD 방식의 전극을 이용하여 패키지 제조 공정에 적합한 인라인 형태의 장비로 구성되었다. 대기압 플라즈마를 처리한 결과 접촉각 기준으로 $71^{\circ}$의 소수성 절연 필름 표면이 $30^{\circ}$ 정도의 친수성 표면으로 개질되었다. 대기압 플라즈마 처리 유무에 따른 습식 디스미어 공정의 특성을 평가하기 위하여 절연 필름의 두께, 드릴 구멍 지름, 표면 조도의 변화를 측정하였는데, 대기압 플라즈마 처리 시 기판 전면에서 공정 특성의 균일도가 향상되는 것을 확인하였다. 또한 대기압 플라즈마 처리 유무에 따른 드릴 구멍의 SEM 사진 분석 결과 대기압 플라즈마 처리 시 구멍 내부의 스미어가 효과적으로 제거됨을 실험적으로 확인하였다.

• 한국정밀공학회지
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• 제30권1호
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• pp.113-119
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• 2013

To develop a new nuclear fuel, it needs to make a test fuel rod and carry out burn-up test in the test loop of a research reactor to check the irradiation characteristics of the nuclear fuel. At that time, several sensors such as thermocouples, LVDTs and SPNDs are needed to be attached in and out of the fuel rod and connect them with instrumentation cables. Then, the instrumentation cables deliver the signals measured by the sensors to the measuring device located outside of the reactor pool. In particular, to install a thermocouple in a fuel rod, it needs to drill off holes on the alumina blocks and sintered $UO_2$ pellets. However, because the hardness of a sintered $UO_2$ pellet is 700 Hv (or HRC 61) and that of an alumina block is 1480 Hv, a special drilling machine which adapts a diamond coated drill bit had developed. In this study, several case experiments have been carried out to find an optimal drilling condition of the drilling machine. And, using the optimal drilling condition, minimum numbers of the holes that a drill bit can drill off are verified.

• Safety and Health at Work
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• 제6권4호
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• pp.268-278
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• 2015

Background: This study aimed to assess the whole-body vibration (WBV) exposure among large blast hole drill machine operators with regard to the International Organization for Standardization (ISO) recommended threshold values and its association with machine- and rock-related factors and workers' individual characteristics. Methods: The study population included 28 drill machine operators who had worked in four opencast iron ore mines in eastern India. The study protocol comprised the following: measurements of WBV exposure [frequency weighted root mean square (RMS) acceleration ($m/s^2$)], machine-related data (manufacturer of machine, age of machine, seat height, thickness, and rest height) collected from mine management offices, measurements of rock hardness, uniaxial compressive strength and density, and workers' characteristics via face-to-face interviews. Results: More than 90% of the operators were exposed to a higher level WBV than the ISO upper limit and only 3.6% between the lower and upper limits, mainly in the vertical axis. Bivariate correlations revealed that potential predictors of total WBV exposure were: machine manufacturer (r = 0.453, p = 0.015), age of drill (r = 0.533, p = 0.003), and hardness of rock (r = 0.561, p = 0.002). The stepwise multiple regression model revealed that the potential predictors are age of operator (regression coefficient ${\beta}=-0.052$, standard error SE = 0.023), manufacturer (${\beta}=1.093$, SE = 0.227), rock hardness (${\beta}=0.045$, SE = 0.018), uniaxial compressive strength (${\beta}=0.027$, SE = 0.009), and density (${\beta}=-1.135$, SE = 0.235). Conclusion: Prevention should include using appropriate machines to handle rock hardness, rock uniaxial compressive strength and density, and seat improvement using ergonomic approaches such as including a suspension system.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.264-268
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• 2003

Recently reduction of industrial products in size and weight has been increased by application of micro-drills in gadgets of high precision and a great interest of a micro-drilling has been raised. Due to the lack of tool stiffness and the chip packing, the micro-drilling requires not only the robust tool structure which has not affected by vibration but also effective drilling methods designed to prevent tool fracture from cutting troubles. This paper presents an optimum design shape of a 0.15 mm micro-drill associated with a new manufacturing process to improve the production rate and to lengthen the tool life and suggestions on the micro-drilling characteristic properties associated with the tool life and workpiece quality.

• 한국표면공학회지
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• 제28권2호
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• pp.77-82
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• 1995

In this study, we examined the relationships between the coating film's properties, such as microhardness, adhesion of coating fil $m_strate, and machining tool's life time. Samples were prepared by coating TiN on the 5.5 diameter twist drills using reactive ion plating technology, For measuring microhardness and adhesion of fil $m_strate, HSS plate was used for substrate. TiN coated drill's life time was dependent on the adhesion of fil $m_strate and averagely increased by several ten times more than uncoated drill's. The major parameter affecting TiN coated drill's life time was the strong adhesion between coating film and substrate.ate.

• 한국기계가공학회지
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• 제10권1호
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• pp.73-79
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• 2011

In this study, coring with diamond core drill on the sintered $Al_2O_3$ ceramic plate were carried out with different coring conditions such as various cutting speed and feed rate to evaluate their effectiveness on the wearing behavior of diamond tool and coring quality. The wearing rate of diamond core drill were getting better with increasing cutting speed and feed rate but the quality of cored hole were getting worse as increasing cutting speed and feed rate.

• 한국공작기계학회논문집
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• 제13권3호
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• pp.133-140
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• 2004

Recently reduction of industrial products in size and weight has been increased by application of micro-drills in gadgets of high precision and a great interest of a micro-drilling has been raised. Due to the lack of tool stiffness and the chip packing, the micro-drilling requires not only the robust tool structure which has not affected by vibration but also effective drilling methods designed to prevent tool fracture from cutting troubles. This paper presents an optimum design shape of a 0.15 mm micro-drill associated with a new manufacturing process to improve the production rate and to lengthen the tool life and suggestions on the micro-drilling characteristic properties associated with the tool life and workpiece quality.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1253-1256
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• 2005

An Experiment was carried out to study burr minimization in drilling on the inclined exit surface. Several different drills, exit surface angles and cutting conditions were selected to determine their influences on burr formation. In drilling operation, there are not only flat exit surfaces but also inclined exit surfaces which is described as inclination angle. Inclination of exit surface causes a quiet different burr formation when comparing with flat surface. Burr formation mechanisms are analyzed according to the drill geometries and cutting conditions. Several schemes for burr minimization on inclined exit surface were proposed. Burr geometry in each drill and cutting condition are measured by laser measurement system.