http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
나노초 펄스 파이버 레이저를 이용한 탄소섬유강화플라스틱의 미세 구멍 어레이 레이저 드릴링
정도관(Do Kwan Chung) 한국기계가공학회 2024 한국기계가공학회지 Vol.23 No.5
Micro-hole array processing using laser irradiation off-time control was studied to obtain excellent machining shape without thermal damage during laser drilling of CFRP. When continuous micro-holes are machined, closer hole spacings worsen the machined shape owing to thermal damage. For a microhole, a single point is repeatedly irradiated with a laser. The laser irradiation off-time control method sets the laser off time for a set of irradiations, which suppresses heat accumulation and prevents thermal damage. This technique was used to process a micro-hole array with a hole spacing of 0.3 mm without thermal damage. Furthermore, the laser off-time was applied to the laser scanning method, which has a laser off-time for each set of laser scans, and a micro-hole array with a hole spacing of 0.14 mm was fabricated without thermal damage. For small hole spacings, the laser scanning method using the laser off-time yielded better machining results than the laser irradiation off-time control. The laser scanning method was unsuitable for this experimental setup when the hole spacing exceeded 0.4 mm. The laser irradiation off-time control method was suitable for large hole spacing.
EDM Using Wire Electrical Discharge Milling Electrode
정도관(Do Kwan Chung) Korean Society for Precision Engineering 2022 한국정밀공학회지 Vol.39 No.1
In this study, a wire electrical discharge milling electrode was developed, and electric discharge machining characteristics were studied by using the electrode. The wire electrical discharge milling electrode is a form, in which the wire is conveyed by using a cylindrical rod with a hemispherical end as a guide, and it also rotates in one direction around the guide axis. If the wire electrical discharge milling electrode is used in electrical discharge machining (EDM), there is no need to consider electrode wear compensation. The EDM characteristics according to capacitance of the RC circuit and the rotational speed of the wire electrical discharge milling electrode were examined. The machining conditions were selected, and a hemispherical shape with good shape accuracy and fine surface finish was fabricated in two stages of roughing and finishing. By applying the wire electrical discharge milling electrode to the electric discharge milling process, straight and curved shapes were successfully machined.
Micro Machining of CFRP Using Nanosecond Pulsed Fiber Laser
정도관(Do Kwan Chung),박진성(Jin Sung Park),김기훈(Ki Hun Kim) Korean Society for Precision Engineering 2019 한국정밀공학회지 Vol.36 No.9
CFRP (Carbon fiber reinforced plastic) has been widely used in different industries such as aerospace, automobile, sports and medical. Laser processing of CFRP has a great potential for industrial applications. In this paper researched the micro cutting and drilling of CFRP with 0.5 mm thickness using 1064 nm ytterbium nanosecond pulsed fiber laser. It also investigated machining characteristics of micro cutting and drilling according to laser power, frequency, scan speed and number of scan (or irradiation). Complete cutting and through-hole drilling were achieved with low frequency when the laser power was low and with low and middle frequency when the laser power increased. However, those were not achieved a frequency of 100 kHz. The cutting width increased when the power increased and decreased when the frequency and the scan speed increased. The hole size increased when the power and the number of irradiation increased and decreased when the frequency increased. In the case of micro hole array, the hole was blocked during the next hole machining when the hole spacing was narrow. The resin was melted by the heat thus blocking the pre-drilled hole. We devised the laser scan method, and the micro hole array with narrow hole spacing was fabricated successfully.
정도관(Do Kwan Chung),김보현(Bo Hyun Kim),주종남(Chong Nam Chu) Korean Society for Precision Engineering 2006 한국정밀공학회지 Vol.23 No.3
In this paper, micro electrical discharge milling using deionized water as dielectric fluid was investigated. In EDM, dielectric fluid is an important factor which affects machining characteristics. When deionized water was used as dielectric fluid, machining characteristics were investigated according to voltage, capacitance, and resistivity of deionized water. Machining gap increased with increasing voltage and capacitance. As the resistivity of deionized water decreased, the machining gap increased. The wear of a tool electrode and machining time can be reduced by using deionized water instead of EDM oil. Surface roughness was also improved when deionized water was used.
정도관(Chung, Do-Kwan),김보현(Kim, Bo-Hyun),주종남(Chu, Chong-Nam) 한국신재생에너지학회 2005 한국신재생에너지학회 학술대회논문집 Vol.2005 No.06
Micro EDM milling using deionized water as dielectric fluid was investigated. After machining micro grooves using deionized water with different voltage. capacitance. and resistivity of deionized water, machining characteristics were investigated. The wear of a tool electrode and the machining time can be reduced by using deionized water instead of kerosene. Micro hemispheres were machined in deionized water and kerosene and their machining characteristics were compared.
송기영(Ki Young Song),정도관(Do Kwan Chung),박민수(Min Soo Park),주종남(Chong Nam Chu) Korean Society for Precision Engineering 2010 한국정밀공학회지 Vol.27 No.10
Electrical discharge drilling (ED-drilling) is a widespread machining method used to bore small holes with a high aspect ratio. This paper presents additional methods by which ED-drilling can improve machining speed, tool wear, and machined surface quality. Firstly, for high machining speed, and low tool wear, a new-type electrode that was ground on one side or both sides of the cylindrical electrodes was suggested to expel debris. The debris which is generated during the machining process can cause sludge deposition and secondary discharge problems: major reasons to decrease machining speed. This new-type electrode also reduced tool wear that was due to the decrease of unstable discharge in a machining gap by helping to expel waste water and debris from the gap. Secondly, to improve the machined surface roughness, an electrolyzation process was included after drilling. This process made the machined surface smooth by means of an electrochemical reaction between an electrode and a workpiece. In this study, the machining speed, electrode wear, and surface roughness were improved by the newtype electrode and the electrolytic process.
송기영(Ki Young Song),정도관(Do Kwan Chung),박민수(Min Soo Park),주종남(Chong Nam Chu) Korean Society for Precision Engineering 2009 한국정밀공학회지 Vol.26 No.8
In this study, a simple and effective method was proposed to minimize electrolytic corrosion on the workpiece during ED-drilling using water as a working fluid. The adhesion of a cover plate onto the surface of the workpiece was greatly effective for suppressing electrolytic corrosion during ED-drilling. The experiment revealed that the adhesion of the cover plate prevented corrosion without causing significant changes in machining characteristics. Using the machining method proposed in this paper, electrolytic-corrosion-free holes can be machined without change in the machinery system. By using corrosion-free hole as a start hole for wire EDM, a lead frame die with high quality was fabricated successfully.
김산하(Sanha Kim),정도관(Do Kwan Chung),김보현(Bo Hyun Kim),오광환(Kwang Hwan Oh),정성호(Sungho Jeong),주종남(Chong Nam Chu) Korean Society for Precision Engineering 2009 한국정밀공학회지 Vol.26 No.10
Although nanosecond pulsed laser drilling and milling are rapid and non-wear processes in micromachining, the quality cannot meet the precision standard due to the recast layer and heat affected zone. On the other hand, electrical discharge machining (EDM) is a well-known high precision machining process in micro scale; however, the low material removal rate (MRR) and tool wear remain as drawbacks. In this paper, hybrid process of laser beam machining (LBM) using nanosecond pulsed laser and micro EDM was studied for micro drilling and milling. While the quality of the micro structure fabricated by this hybrid process remains as high as direct EDM, the machining time and tool wear can be reduced. In addition, variable depth of layer was introduced as an effective method improving efficiency of hybrid milling.
김보현(Bo Hyun Kim),정도관(Do Kwan Chung),주종남(Chong Nam Chu) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.6
Micro EDM milling using deionized water as dielectric fluid were investigated. By micro EDM milling, micro structures such as micro grooves were machined on stainless steel. After machining micro grooves with different voltage, capacitance, and resistivity of water, machining characteristics such as gap, tool wear, maximum feedrate and surface quality were investigated. The wear of a tool electrode can be reduced by using deionized water. With different dielectric fluids, kerosene and deionized water, micro hemispheres were machined and their machining characteristics were compared.