• 소성∙가공
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• 제13권3호
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• pp.253-261
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• 2004

The machining technology for the brittle materials such as ceramics are applied to the fields of MEMS(micro electromechanical system) by the progress of new machining technologies such as Etching, Diamond machining, Micro drilling, EDM(Electro discharge machining), ECDM(Electro discharge machining), USM(Ultrasonic machining), LBM(Laser beam machining), EBM(Electron beam machining). Especially, the USM technology can be applied to the dieletric brittle materials such as silicon, borosilicate glass, silicon nitride, quartz and ceramics with high aspect ratio. The micro machining system with machining force controlled position servo is developed in this paper and the optimized ultrasonic machining algorithm is constructed by the force controlled position servo control. The load cell is adapted in the force measuring and the servo control algorithm, suit for the ultrasonic machining characteristics, is estabilished with using the PID auto-tunning functions at the PMAC system which is generally adapted in the field of robot industries. The precision force signal amplifier is constructed with high precision operational amplifier AD524. The vacuum adsorption chuck which is made of titanum and internal flow line is engraved, is used in the workpiece fixing. The mahining results by USM shows that there are some deviation between the force command and the actual machining force that the servo control algorithm should be applied in the machining procedures. Therefore, the constant force controlled position servo system is developed for the micro USM system and by the examination machining process in USM, the stable USM system is realized by tracking the average value of machining force.

• 한국기계가공학회지
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• 제14권3호
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• pp.105-111
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• 2015

Ultrasonic machining (USM) does not involve heating or any electrochemical effects, and subsequently causes low surface damage, has small residual stress, and does not rely on the conductivity of the workpiece. These characteristics are suitable for the machining of brittle materials, such as glass or ceramics. However, USM for brittle materials generates cracks on the workpiece while machining, especially at the hole exit with a small diameter. In this study, wax coating was used to deposit wax on the back side of the workpiece to decrease the occurrence of cracks at the exit holes in USM, and it was finally removed with a cleaning process. The experimental results show that this technique is beneficial for restricting the occurrence of cracks in glass or ceramics.

• 대한기계학회논문집A
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• 제31권10호
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• pp.1039-1045
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• 2007

Ultrasonic machining (USM) is suitable for machining hard, brittle and non-conductive materials such as silicon, glass and ceramics. Usually, when micro holes are machined on glass by USM, roundness of hole entrance is poor and cracks appear around the hole exit. In this paper the machining characteristics were studied for roundness improvement and exit crack prevention. From experiments, the tool bending and the shape of tool tip affect hole roundness. When the tool tip is hemispherical, good roundness of holes was obtained. The feedrate and the rotational speed of the tool affect the exit crack. With the machining conditions of 150 rpm in spindle speed and $0.5\;{\mu}m/s$ in feedrate, micro holes with less than $100\;{\mu}m$ in diameter were machined without an exit crack.

• 한국정밀공학회지
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• 제19권7호
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• pp.133-140
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• 2002

Ultrasonic Machining (USM) is widely used in cutting of non-conductive, brittle workpiece materials such as engineering ceramics. However, USM has a limitation in its application to micro machining because problems are occurred in attaching micro tools to the machine and maintaining high precision. Therefore Micro Ultrasonic Machining (MUSM) with WEDM is proposed in this research. The experiments are produced as the change of shaft diameter and abrasive size.

• 한국공작기계학회논문집
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• 제13권2호
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• pp.104-111
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• 2004

Ultrasonic machining is a non-thermal, non-chemical, md non-electorial material removal process, and thus results in minimum modifications in mechanical properties of the brittle material during the process. Also, ultrasonic machining is a non-contact process that utilize ultrasonic vibration to impact a brittle material. In this research characteristics of micro-hole machining for brittle materials by ultrasonic machining(USM) process have been investigated. And the effect of ultrasonic vibration on the machining conditions is analyzed when machining fir non-conductive brittle materials using tungsten carbide tools with a view to improve form and machining accuracy.

• 대한기계학회논문집A
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• 제37권2호
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• pp.213-218
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• 2013

초음파 가공(Ultrasonic Machining:USM)은 새로운 기계가공기술 분야 중의 하나이다. 초음파 가공 과정은 비열, 비화학, 그리고 비전도의 방법이기 때문에 공작물 재료의 물리적, 화학적 변화가 없다. 이러한 특성으로 인해 초음파 가공기술은 유리, 세라믹 등과 같은 취성재료의 가공에 적합하다. 그러나 단점으로는 초음파 진동을 이용하여 취성재료를 가공하는 경우 크랙이 빈번하게 발생한다. 본 논문에서는 유리와 세라믹의 미세 구멍가공에서 다구찌 방법을 이용하여 크랙발생을 최소화하는 최적의 가공조건을 얻고자 하였다. 이를 통해 공작물의 입구 및 출구에서 발생하는 크랙 현상을 감소시켰다.

• 한국기계가공학회지
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• 제14권4호
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• pp.160-166
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• 2015

Ultrasonic machining (USM) has been considered a new, cutting-edge technology that presents no heating or electrochemical effects, with low surface damage and small residual stresses on brittle workpieces. However, nowadays, many researchers are paying careful attention to the disadvantages of USM, such as low productivity and tool wear. On the other hand, in this study, a high-performance rotary ultrasonic drilling (RUD) spindle is designed and assembled. In this system, the core technology is the design of an ultrasonic vibration horn for the spindle using finite element analysis (FEA). The maximum spindle speed of RUM is 9,600 rpm, and the highest harmonic displacement is $5.4{\mu}m$ noted at the frequency of 40 kHz. Through various drilling experiments on glass workpieces using a CVD diamond-coated drill, the cutting force and cracking of the hole entrance and exit side in the glass have been greatly reduced by this system.

• 한국기계가공학회지
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• 제2권1호
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• pp.32-38
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• 2003

Engineering ceramics have many unique characteristics both in mechanical and physical properties such as high temperature hardness, high thermal, chemical and electrical resistance. However, its machinability is very poor in conventional machining due to its high hardness and severe tool wear. In the current experimental study alumina($Al_2O_3$) was ultrasonically machined using SiC abrasives under various machining conditions to investigate the material removal rate and surface quality of the machined samples. Under the applied amplitude of 0.02mm, 27kHz frequency, three slurry ratios (abrasives water by weight) of 11, 13 and 15 with different tool shapes and applied pressure levels, the machining was conducted. Using the mesh number of 240 abrasive, slurry ratio of 11 and static pressure of $25kg/cm^2$, maximum material removal rate of $18.97mm^3/mm$ was achieved with mesh number of 600 SiC abrasives and static pressure of $30kg/cm^2$, best surface roughness of $0.76{\mu}m$ Ra was obtained.

• 한국정밀공학회지
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• 제17권7호
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• pp.20-27
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• 2000

한국은행의 지식기반산업의 국민 경제적 역할 분석에 따르면, 91년부터 99년까지 지식기반산업의 연평균 성장률은 13.7%로 다른 산업의 4.1%보다 3배 이상 높은 것으로 조사되었다. 그중 항공기, 사무계산 및 회계용 기기, 의약품, 영상 음향 통신장비 등 첨단제조업은 이 기간 중 연평균 20.1% 성장을 기록하였다. 이와 같은 첨단제조업에서는 제품 내 부품의 정밀가공 기술이 필수적이다. 그 중에서도 미세 가공에 대한 관심은 지속적으로 증가하고 있는 추세이다.(중략)