• Journal of the Korean Society for Precision Engineering
• /
• v.22 no.3 s.168
• /
• pp.15-20
• /
• 2005

This paper describes the PCB drilling using an ultra high-speed air bearing spindle system and micro drill. For this research, we have developed the ultra high-speed air bearing spindle of 125,000 rpm and made an experiment for the application possibility in the PCB drilling. In order to estimate the drilling performance, we have investigated the size and damage of drilled hole, and the wear of drill at 90,000rpm. Results are as follows; we have confirmed the possibility in the PCB drilling of air bearing spindle. In case of micro-drilling PCB at $0.1mm\sim0.3mm$, the increase in the number of drilling has resulted in a bigger size of holes and also a bigger size of damage. It has been found that the wear of micro drill tends to concentrate in the main cutting edge.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.08a
• /
• pp.303-303
• /
• 2011

최근 세포 포집 소자 제작에 있어 세포의 종류와 크기의 다양성을 고려하여 정확하게 포집하기 위한 고정밀화, 소형화 된 도구 제작 기술 개발이 중요한 현안으로 떠오르고 있다. 본 연구에서는 선행 기술에서의 세포 포집 한계를 극복하기 위한 방안으로 펨토초 레이저 가공을 통한 미세 세포 포집 장치 제작에 관한 실험을 진행하였다. 펨토초 레이저의 짧은 파장의 대역 범위와 전력 특성이 미세 소자 제작을 가능하게 함에 따라 수백, 수천 개의 세포 포집에 있어 보다 안정적이고 신뢰도 높은 포집 장치 구현을 실현시킬 수 있다. 실험에서는 펨토초 레이저의 가공 조건을 가변하며 MEMS 소자에 홀(hole)을 형성시켰다. flatness 200인 Polycarbonate 재질의 기판 위에 CNC공작기계를 사용하여 유로를 제작하고 상부에 젤라틴 코팅 부분 2를 포함한 총 두께 12의 membrane 필름을 부착하였다. 이후 775 nm 파장의 펨토초 레이저를 사용하여 10${\times}$10 개수의 홀을 형성 한 후 홀 주위의 thermal damage와 레이저의 파워에 따른 홀의 형태와 크기 변화를 비교하였다. 실험 결과 membrane 막의 젤라틴 코팅 측면 홀의 평균 직경은 레이저의 파워와 비례하여 증가하였으며, 레이저 파워가 일정한 임계치에 도달하면 특정 시점에서 수렴됨을 확인하였다. 또한 PET 측면의 직경은 서서히 증가하고 빠르게 일정한 값으로 수렴됨을 확인하였다. 본 실험에서는 펨토초 레이저의 특성 파라미터와 레이저의 가공 조건을 수립함으로써 실험에서 사용 된 레이저를 이용한 드릴링 방안을 제시한다.

• The korean journal of orthodontics
• /
• v.38 no.4
• /
• pp.228-239
• /
• 2008

Objective: The aim of this study was to evaluate the strain induced in the cortical bone surrounding an orthodontic microimplant during insertion. Methods: A 3D finite element method was used to model the insertion of a microimplant (AbsoAnchor SH1312-7, Dentos Co., Daegu, Korea) Into 1 mm thick cortical bone with a pre-drilled hole of 0.9 mm in diameter. A total of 1,800 analysis steps was used to simulate the 10 turns and 5 mm advancement of the microimplant. A series of remesh in the cortical bone was allowed to accommodate the change in the geometry accompanied by the implant insertion. Results: Bone strains of well higher than 4,000 microstrain, the reported upper limit for normal bone remodeling, was observed in the bone along the whole length of the microimplant. At the bone in the vicinity of the screw tip, strains of higher than 100% was recorded. The insertion torque was calculated at approximately 1.2 Ncm which was slightly lower than those measured from the animal experiment using rabbit tibias. Conclusions: The insertion process of a microimplant was successfully simulated using the 3D finite element method which showed that bone strains from a microimplant insertion might have a negative impact on physiological remodeling of bone.

• Restorative Dentistry and Endodontics
• /
• v.30 no.3
• /
• pp.178-183
• /
• 2005

This study was done to evaluate whether vital bleaching agents could influence on the translucency of the bovine enamel. The anterior bovine teeth that were extracted one day before and without any gross discoloration were obtained and then were preserved in physiologic saline. 6 mm cylindrical tooth specimens were fabricated with diamond puncher perpendicularly on labial surface of bovine tooth. After embedded in transparent acrylic resin with labial surface being exposed, they were cut to a thickness of 1.2 mm with low speed diamond saw (Isomat, Buehler Co., Lake Bluff, IL, USA). They were smoothly ground to 1 mm thickness of enamel with sandpaper. 24 specimens were randomly divided into 3 groups and control group respectively. Opalescence (10% carbamide peroxide, Ultradent, South Jordan, USA), Rembrandt (10% carbamide peroxide, DenMat, USA) and Opalescence F (15% carbamide peroxide with fluoride, Ultradent, USA) were applied on labial sides of the bovine enamel for 7 days (bleaching agents were reapplied every 24 hours) and the opposite surface was contacted to cotton that soaked in distilled water. The control group was soaked in distilled water. Three stimulus value X, Y and Z were evaluated with colorimeter (Color ' Color Differencerneter, Model TC-6FX, Tokyo Denshoku Co., Japan) on the labial surface of all specimen three times on white and black background plate before the bleaching agents were applied and on 3rd, 5th and 7th day after applied. The degree of translucency was normally assessed by measuring the inverse property, opacity (contrast ratio). 10% Opalescence, 15% Opalescence-F, and control group showed no significant variation in the translucency of bovine enamel, However Rembrandt decreased the translucency of it (p < 0.01).