• Title/Summary/Keyword: Micro-drill tip

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Micro-drilling of alumina green body with diamond abrasive drills (다이아몬드 입자 전착 드릴에 의한 알루미나 성형제의 미소구멍가공)

  • 이학구;방경근;김포진;이대길
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2002.05a
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    • pp.926-931
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    • 2002
  • Although ceramic plates with many micro-hales are used as MCP (Micro-channel plate) for electron amplification, catalytic converters, filters, electrical insulators and thermal conductors in integrated circuits, the drilling of micro-hales in the ceramics is difficult because of their low thermal conductivity, high hardness and brittleness. Therefore, in this work, the machining of ceramic green body fellowed by sintering of green body was employed fur fabricating ceramic plates with many micro-holes. The micro-drilling of alumina green body was performed with diamond abrasive WC drills, and the cutting force w.r.t. drilling times was measured for the determination of toot life. From the investigation of the wear of micro-drill tip w.r.t. drilling times, the wear mechanism of tip during micro-drilling of ceramic green body was suggested.

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Model for predicting tool life of diamond abrasive micro-drills during micro-drilling of ceramic green bodies (세라믹 성형체의 미소구멍 가공 시 다이아몬드 입자 전착 드릴의 공구 수명 예측 모델)

  • 이학구;이대길
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2003.06a
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    • pp.593-598
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    • 2003
  • Ceramic plates containing many micro-holes are used in diverse applications such as MCP (Microchannel Plate). catalytic converters, filters, electrical insulators in integrated circuits, and so on. One of the efficient methods for machining many holes in ceramic plates is wet drilling of ceramic green bodies followed by sintering them. Since the strength of ceramic green bodies is much lower than the strength of sintered ceramic plate, ceramic green bodies can be drilled with high feed rate. The axial force during micro-drilling of ceramic green bodies increases rapidly at high feed rate, which induces the crack in workpiece. Therefore, the tool lift of micro-drill with respect to feed rate may be determined by the predicting increase of axial force. In this work, the axial force during micro-drilling was calculated using the chip flow model on the micro-drill tip. from which the tool life of diamond abrasive micro-drill during micro-drilling of ceramic green bodies was calculated.

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Effect of Laser Pre-Drilling on Insertion Torque of Orthodontic Miniscrews: A Preliminary Study

  • Kim, Keun-Hwa;Choi, Sung-Hwan;Cha, Jung-Yul;Hwang, Chung-Ju
    • Journal of Korean Dental Science
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    • v.10 no.2
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    • pp.66-73
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    • 2017
  • Purpose: To evaluate the effect of different-sized drill tips and laser irradiation times on the initial stability of orthodontic miniscrews placed in Er,Cr:YSGG-laser pre-drilled holes in an animal model. Materials and Methods: Laser pre-drilled holes were made in dog mandibular bone with an Er,Cr:YSGG laser using irradiation times of 5, 7, 9, 11, and 13 seconds, and tip diameters of 0.4 and 0.6 mm. The maximum diameter and depth of the pre-drilled holes was measured with micro computed tomography. The maximum insertion torque was measured during placement the miniscrew. Result: Laser pre-drilled holes were conical shaped. The maximum diameter of pre-drilled holes increased with longer laser irradiation times (P>0.05) and larger tip diameters (P<0.05). The depth of pre-drilled holes increased with longer laser irradiation times and larger tip diameters (P<0.05). When the 0.4 mm tip, but not the 0.6 mm tip, was used, the insertion torque decreased significantly with longer laser irradiation times (P<0.05). Conclusion: Tip diameter impacted insertion torque more than irradiation time. It takes at least 9 seconds using a 0.6 mm tip to create a 0.8 mm diameter and 1.0 mm depth hole in thick cortical bone.

Tensile Strength Properties of the Diffusion Bonding Copula Shape for Micro PCD Tool Fabrication (초소형 PCD 공구 제작을 위한 확산접합부의 형상에 따른 인장강도 특성)

  • Jeong, Ba Wi;Kim, Uk Su;Chung, Woo Seop;Park, Jeong Woo
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.14 no.2
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    • pp.25-30
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    • 2015
  • This study involved the fabrication of precision machine tools using a polycrystalline diamond tip [sintered PCD and cemented carbide (WC-Co) tip] and WC-Co shanks via diffusion bonding with a paste-type nickel alloy filler metal. Diffusion bonding is a process whereby two materials are pressed together at high temperature and high pressure for a sufficient period of time to allow significant atomic diffusion to occur. For smooth progress, a filler metal of nickel alloy was used at the interface. Optical microscopy images were used to observe the copula of the bonded layer. It was confirmed that cracks occurred near the junction in all cases. The tensile strength of the bond was measured using a universal testing machine (UTM) with WC-Co proportional test specimens.

An Experimental Study on the MSG Reinforcement of Steel Pipe Pile Installed by PRD (MSG공법에 의한 PRD강관말뚝 보강에 관한 사례 연구)

  • Chun, Byungsik;Kang, Heejin;Kong, Jinyoung
    • Journal of the Korean GEO-environmental Society
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    • v.8 no.6
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    • pp.5-12
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    • 2007
  • Mudstone has characteristics that it has high enough strength and stiffness in a dry condition, but the strength and stiffness decrease in a wet condition with groundwater infiltration. The sliding of cut slope frequently encountered in Pohang area has been reported due to the rapid reduction of shear strength in mudstone after being exposed to the air. The study in this paper shows that mudstone having enough strength in a boring stage has lost the strength after installing PRD (percussion rotary drill) steel pipe pile inducing an insufficient bearing capacity. Field test has been performed to investigate the most favorable method for increasing a pile bearing capacity in mudstone with various methods such as MSG (Micro Silica Grouting) around the tip and side of a pile, the perimeter grouting combined with Micro pile reinforcement, and concrete filling after tip reinforcing grouting. MSG has been turned out to be the most favorable method for increasing a pile bearing capacity in mudstone, confirmed by the static load test.

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