• 대한치과교정학회지
• /
• 제39권4호
• /
• pp.203-212
• /
• 2009

골밀도가 높고 두꺼운 피질골에 마이크로임플란트를 self-drilling 방식으로 식립하는 경우 과도한 수준의 골부하 (bone loading)가 발생할 위험이 있으며 이는 인접골의 정상적인 골개형(bone remodeling)에 장애를 초래할 수 있다. 이에, 본 연구에서는 유한요소해석으로 두께 1.0 mm의 피질골에 Absoanchor SH1312-7 마이크로임플란트((주)덴토스, 대구, 대한민국)가 self-drilling 방식으로 식립되는 과정(10회전, 식립깊이 5 mm)을 모사(simulation)하였으며 식립 단계별로 피질골에 발생되는 스트레인을 조사하였다. 식립중 마이크로임플란트 첨부의 절삭연(cutting flute)에 의한 골삭제로 생기는 나사길(threaded groove)의 치수를 얻기 위하여 가토 경골에 마이크로임플란트를 식립/제거한 후 Micro CT (Explore Locus RS, GE Healthcare, Ontario, Canada)를 이용하여 기하형상을 측정하였으며 이를 치밀골의 유한요소모델에 반영하였다. 해석결과, 치밀골에 발생되는 스트레인은 임플란트 식립깊이에 따라 증가하였고, 초기단계에서 나사산에 인접한 골에 국한되던 과부하 부위(스트레인이 4,000${\mu}$-strain을 상회하는 영역)가 식립깊이 증가에 따라 인접골 전체, 즉 나사산 인접부는 물론 골(valley) 부위에 접하는 모든 영역으로 확장되었다. 본 연구를 통해, self-drilling 방식으로 마이크로임플란트를 식립할 때 치밀골에 발생하는 스트레인 크기는 생리적인 골개형을 저해할 수 있는 수준임을 확인할 수 있었다.

• 한국기계가공학회지
• /
• 제9권3호
• /
• pp.56-61
• /
• 2010

Recently, UV pulse laser is widely used in micro machining of the research, development and industry field of IT, NT and BT products because the laser short wavelength provides not only micro drilling, micro cutting and micro grooving which has a very fine line width, but also high absorption coefficient which allows a lot of type of materials to be machined more easily. To analyze the dynamic deformation during a very short processing time, which is nearly about several tens nanoseconds, the commercial Finite Element Analysis (FEA) code, LS-DYNA 3D, was employed for the computitional simulation of the UV laser micro machining behavior for thin copper material in this paper. A finite element model considering high strain rate effect is especially suggested to investigate the micro phenomena which are only dominated by mechanically pressure impact in disregard of thermally heat transfer. From these computational results, some of dynamic deformation behaviors such as dent deformation shapes, strains and stresses distributions were observed and compared with previous experimental works. These will help us to understand micro interaction between UV laser beam and material.

• 한국기계가공학회지
• /
• 제11권1호
• /
• pp.62-67
• /
• 2012

Recently UV laser is widely used to process micro parts using various materials such as polymers, metals and ceramics because it has a very high intensity at the focused spot area. It is generally known that there are still some difficulties for alumina($Al_2O_3$) ceramics to directly make micro patterns like holes and lines on the surface of working material using 355nm UV laser because the alumina has a very low absorption coefficient at that wavelength. But nowadays new alumna with nano-porous holes is developed and applied to advanced micro functional parts of IT, BT and BT industries. In this paper, we are going to show the mechanism of photo-thermal ablation for nano-porous ceramics. Inside hole there is a lot of multiple reflections along the depth of hole. Experimentally we can find the micro hole drilling and micro grooving on the surface of nano-porous alumina.

• 한국생산제조학회지
• /
• 제24권5호
• /
• pp.502-507
• /
• 2015

In this study, a microscale drilling process was conducted to evaluate the cutting characteristics of functionally graded materials. A mixture of M2 and Cu powders were formed and sintered to produce disk specimens of various compositions. Subsequently, a microscale hole was created in the specimen by using a desktop-size micro-machining system. By using design of experiments and analysis of variance, it was found that the M2-Cu composition, spindle speed, and the interactions between these two factors had significant effects on the magnitude of cutting forces. However, the influence of feed rate on the cutting force was negligible. A mathematical model was established to predict the cutting force under a wide range of process conditions, and the reliability of the model was confirmed experimentally. In addition, it was observed that increasing the wt% of Cu in an M2-Cu specimen increased the high-frequency amplitude of cutting forces.

• 센서학회지
• /
• 제13권1호
• /
• pp.72-77
• /
• 2004

In this paper, we fabricated an apparatus of the electro-chemical discharge drilling for boring narrow through-hole into a glass. In the electrolyte, electro-chemical discharge creates high temperature condition by the electro-discharge energy. Therefore, glass are removed by the accelerated chemical reaction with glasses and chemicals in the high temperature condition. For optimization of the electro-chemical discharge drilling, the process condition was studied experimentally as a function of the electrolyte concentration, supply voltage and process time. The optimum condition was from DC25V to DC30V of applied voltage, 35 wt% NaOH solution.

• 한국해양공학회지
• /
• 제16권6호
• /
• pp.60-64
• /
• 2002

This paper describes the machining characteristics of the MoSi$_2$--based composites through the process of electric discharge drilling with various tubular electrodes. In addition to hardness characteristics, microstructures of Nb/MoSi$_2$laminate composites were evaluated from the variation of fabricating conditions, such as preparation temperature, applied pressure, and pressure holding time. MoSi$_2$-based composites have been developed in new materials for jet engines of supersonic-speed airplanes and gas turbines for high-temperature generators. These high performance engines may require new hard materials with high strength and high temperature-resistance. Also, with the exception of grinding, traditional machining methods are not applicable to these new materials. Electric discharge machining (EDM) is a thermal process that utilizes a spark discharge to melt a conductive material. The tool electrode is almost -unloaded, because there is n direct contact between the tool electrode and the work piece. By combining a non-conducting ceramic with more conducting ceramic, it was possible to raise the electrical conductivity. From experimental results, it was found that the lamination from Nb sheet and MoSi$_2$ powder was an excellent strategy to improve hardness characteristics of monolithic MoSi$_2$. However, interfacial reaction products, like (Nb, Mo)SiO$_2$and Nb$_2$Si$_3$formed at the interface of Nb/MoSi$_2$, and increased with fabricating temperature. MoSi$_2$composites, with which a hole drilling was not possible through the conventional machining process, enhanced the capacity of ED-drilling by adding MbSi$_2$, relative to that of SiC or ZrO$_2$reinforcements.

• 소성∙가공
• /
• 제13권3호
• /
• pp.253-261
• /
• 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.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2010년도 춘계학술발표대회 초록집
• /
• pp.32-38
• /
• 2010

Hybrid material(ceramic+metal) processes were developed for micro filter using ceramics coating at metal filter surface by thermal spray method, micro hole drilling at ceramic coated filter surface by femtosecond laser, and fiber laser direct welding of ceramic and metal (SUS304, SM45C) by capillary effect. Thermal spray process was used for ceramic powders and metal filters. The used ceramic powders were $Al_2O_3+40TiO_2$(Metco 131VF) powder of maximum particle size $5{\mu}m$ and ${Al_2O_3}99+$(Metco 54NS) power of maximum particle size 45m. Ceramic coated filters using thermal spray method had a great influence on powder material, particle size and coating thickness but had a fine performance as a micro filter. CW fiber laser was used to drill the top ceramic layer and melt the bottom metal layer for joining applications.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1995년도 춘계학술대회 논문집
• /
• pp.58-63
• /
• 1995

절삭가공 중에서도 높은 비중을 차지하는 구멍가공은 전자제품, 공작기계 뿐만 아니라 산업 전반에 걸쳐 소형 화, 다양화, 대량생산화 함에 따라 미세화, 고속화하게 되었다. 본 연구에서는 미세드릴 가공시에 발생하는 스러스트를 측정하여 이송, 절삭속도, 피삭재 두께 변화 등 각 절삭조건이 공구수면과 가공확대오차에 미치는 문제점을 해결하기 위한 방안으로 스텝이송 방식을 채택하여 그 효과에 대한 평가를 목적으로 한다.

• 한국정밀공학회지
• /
• 제21권8호
• /
• pp.65-72
• /
• 2004

For the burrs formed in machining are irregular and very sharp in shape, it is usually very difficult to measure burr accurately. It was proved that micro burr geometry can be measured imprecision by the Conoprobe sensor using conoscopic holography method. We developed 3D burr measurement system using this sensor. The system is composed of Conoprobe sensor, XY table, controller and 3D measurement program. Some measurements using the developed system are conducted for the burrs formed in micro drilling and piercing. Specific software fur burr measurement includes several function, calculation of burr volume, average burr height. Burs formed on a curved surface were compensated and measured successfully using the basic surface compensation function.