• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.04a
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• pp.115-119
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• 1992

산업의 발전과 더불어 새로운 재료의 개발에 대한 요구가 날로 증가하고 있으며 이와 같은 요구에 부응하기위하여 각종의 신소재가 개발되고있다. 이들 신소재 중에서 섬유강화 복합재료는 높은 비탄성과 비강도특성 때문에 구조물의 경량화가 요구되는 우주선, 항공기 등에 주로 이용 되어 왔으며 최근에는 복합재료의 가격이 저렴해 지면서 이 재료의 높은 비탄성과 감쇠특성을 이용하고자 스포츠용품 및 기계 부품에도 섬유강화 복합재료의 이용이 증가 되고 있다. 항공기나 고속회전체의 부품을 복합재료로 제작하였을 경우 복합재료를 다른 금속이나 다른 복합재료부품에 접합(joining)시켜야 하는데 이 때문에구조물의 효율은 Joint에서 주로 죄우된다. Joint를 제작하기 위해서는 복합재료의 표면을 가공한 수 Adhesive를 이용하거나 Bolt로 체결하기 위해 구멍 뚫기 작업이 필요하여 드릴링을 하였을때 이 재료가 매우 연마성이 강하여 심한 공구마멸을 일으키며, 드릴의 입구와 출구쪽에서 각 ply들의 박리 현상이 발생하고, 드릴가공된 벽면으로부터 섬유 또는 레진의 탈락현상등이 발생하는 결점을 가지고 있다. 따라서 본 연구에서는 이러한 결점을 최소화하여 고정밀도의 높은 생산성을 얻기위한 가공기술에 대한 자료를 만들고 최적 절삭조건 및 복합재료가공용 드릴의 설계를 위한 지침을 제시하고자 고속도강 표준드릴을 사용하여 유리섬유 에폭시 복합재료및 탄소섬유 에폭시 복합재료의 드릴링 실험에서 절삭조건이 가공면 생성, 공구마멸, 절삭력에 미치는 영향에 대하여 조사하였다.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.3
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• pp.207-213
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• 2014

A study was carried out to fabricate the cutting tool geometry with micro/nanoscale on the single crystal diamond tool by using the FIB. The FIB technique is an ideal tool for TEM sample preparation that allows for the fabrication of electron-transparent foils. The FIB is appropriate techniques to sample and subsequently define the chemical composition and the structural state of mineral inclusion on the micro/nanoscale. The combination of FIB with a SEM allows for 3D information to be obtained from samples including 3D imaging. Cutting strategies were demonstrated to improve the performance of cutting tool geometry and to generate high aspect ratio micro cutting tool. A finely focused beam of 30keV Ga+ ions was used to mill cutting tool shapes for various micro patterns. Therefore FIB sputtering is used to shape a variety of cutting tools with dimensions in the $1-5{\mu}m$ range and cutting edge radii of curvature of under 50nm.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.1
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• pp.35-40
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• 2016

End milling process is one of the broadly used manufacturing process for precision machined parts and products. Machining performance is often limited by chatter vibration at the tool-workpiece interface. Chatter vibration is a type of machining self-excited vibration which originated from the variation in cutting forces and the flexibility of the machine tool structure. Even though lots of cutting tooling methods are developed and used in machining process, precise analysis of cutting tooling effect in view of chatter vibration behavior. This study presents numerical and experimental approaches to verify and effects of various cutting parameters to affect to chatter vibration stability. Acquired knowledge from this study will apply the optimal cutting conditions to improve a machining process.

• Restorative Dentistry and Endodontics
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• v.27 no.6
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• pp.577-586
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• 2002

The purpose of this in vitro study was to compare the effects of root canal cleanness following two Ni-Ti rotary instruments with different rake angle. Thirty-six sound, extracted human premolars with single root were randomly divided into three groups. The used rotary instruments were HEROShaper (Group 1, Micro-Mega, Besancon, France, n=12) and ProFile (Group 2, Maillefer, Ballaigues, Switzerland, n=12). Control group (n=12) was only extirpated with barbed broach (Mani, Matsutani Seisakusho Co., Japan) Group 1 & 2 teeth were prepared to a #40/.04 taper at the apex followed by 1 mm using crown-down technique. After canal preparation and frequent irrigation with 5.25% sodium hypochlorite, the roots split longitudinally into a bucco-lingual direction. Root halves were cross-sectioned in apical third portion again. All root specimens were processed for SEM investigation and photographed. Separate evaluations by one endodontist were undertaken for smear layer on prepared walls with a five score-index for each using reference photograph in root halves. The penetration depth of smear layer into dentinal tubules was also estimated in the other halves. Following results were obtained: 1. Smear layer was observed on all the prepared walls with two experimental groups except control group. 2. Smear layer characteristics in two experimental groups; 1) HEROShaper group showed snowy, dusty appearance and were shown open dentinal tubuli on the prepared walls of almost specimens, and the thickness of smear layer covering onto dentinal surfaces was within 1-2 ${\mu}m$ in a few specimens. 2) ProFile group showed shiny, burnished appearance and complete root canal wall covered by a homogenous smear layer with no open dentinal tubuli in all specimens. The penetration of smear layer into dentinal tubules was found in all specimens and the thickness was at 2-4 ${\mu}m$ in all specimens. These results demonstrated that a completely clean root canal could not be achieved regardless of positive or negative rake angle, which is in accordance with the majority of previous studies on root canal cleanliness In conclusion, through irrigation with antibacterial solutions or chelating agents is recommended to remove the smear layer on prepared canal wall in spite of Ni-Ti instrumentation.

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

• Journal of the Korean Society for Precision Engineering
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• v.13 no.1
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• pp.53-61
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• 1996

A clear understanding of the surface formation mechanism due to cutting is very important to help produce a good quality surface. Much of the roughness along the length of a bar being cut in a lathe can be explained in terms of macroscopic tool shape and feed rate. However, the roughness along the direction of cutting requires a different explanation. The formation of surface roughness is a problem in flow and fracture of materials in the vicinity of the tool edge. On a microscopic scale the cutting edge is rounded because it is impossible to grind a perfectly sharp cutting edge. Even if a perfectly sharp cutting edge were obtained it would soon become dull as a result of rapid breakdown and wear of the cutting edge. A research project is proposed in which in the main object is to model the surface formation mechanism due to cutting. The tool was assumed to be dull, that is, its edge has a finite radius. In order to study the effect of the radius of cutting edge on the surface formation, tools having different cutting edges were used. For orthogonal cutting experiment, cast iron and glass were chosen as brittle materials. Plowing forces acting in the cutting edge were estimated and its effect on the surface roughness was studied by observing the machined surface using optical microscope.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.4
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• pp.1-7
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• 2011

The mode analysis of end-milling was introduced using recursive parametric modeling. Also, a numerical mode analysis of FRF in end-milling at different conditions was performed systematically. In this regard, a REIVM(recursive extended instrumental variable method) modeling algorithm was adopted and natural modes of real and imaginary part were discussed. This recursive approach can be used for the on-line system identification and monitoring of an end-milling for this purpose. For acquiring a cutting force, an experimental practice was performed. And these end-milling forces were used for the calculation of FRF(Frequency response function) and its mode analysis. Also, the FRF was analysed for the prediction of end-milling system. As a results, this algorithm was successful in each condition for the detection of natural modes of end-milling. After numerical analysis of the FRF, the tooth passing frequency was discriminated in their FRF, power spectrum and mode calculation.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.2
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• pp.30-36
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• 2007

In order to estimate the maximum undeformed chip thickness in grinding operation, it is necessary to obtain the successive cutting point spacing. In the past it was obtained by experiments. In this paper, the average successive cutting point spacing has been obtained using the given grinding input conditions and it is possible to estimate the maximum undeformed chip thickness without using any experimentally obtained data. The validity of the proposed analysis has been verified based on two sets of grinding scratch tests using WA and CBN grinding wheels.

• Journal of Biosystems Engineering
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• v.22 no.2
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• pp.199-209
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• 1997

A one-pass rice whitener with hard metal blades was developed to solve the problems of the existing one-pass rice whitener. The developed one-pass rice whitener was tested and improved through various milling experiments. It showed high performance such as the capacity of 3.5 t/h, the energy consumption of $1.0 kWh/100kg$, milled rice recovery of 91.6%, broken rice rate of 2.2%, the crack rate of 1.9% at the 750 rpm of the roller shaft, compared with those other domestic and foreign one-pass rice whiteners. Especially, it could whiten broun rice of high moisture (16～l7%) with water sprayed at low internal pressure of less than $0.2 kg/cm^2$ and low temperature due to the characteristics of the cutting part composed of 24 hard metal blades. The developed one-pass rice whitener was industrilized and distributed to some rice processing complexs in one fourth price compared with that of imported one-pass rice whiteners.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.3
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• pp.22-29
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• 2004

Runout causes severe differences among cutting force waveforms due to changes of rotational radii. Thus a runout model must be included in a cutting force model to simulate cutting force accurately. In this paper, a runout modeling method and a measurement method using a dialgauge were developed, which were easy to apply. To calculate runout parameters, a computer program algorithm which obtained runout parameters from measurement values was developed. Cutting force waveforms simulated from cutting force model considering runout effect and measured from experiments had good agreements for their wave size and order.