• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.4
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• pp.271-280
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• 2016

Predicting cutting forces in machine tools is essential to productivity improvement and process control in the manufacturing field. Furthermore, milling machining is more complicated than turning machining. Therefore, several studies have been conducted previously to simulate milling forces; this study aims to simulate the cutting forces in milling machines using multi-layered neural networks. In the experiments, the number of layers in these networks was 3 and 4 and the number of neurons in the hidden layers was varied from 20 to 200. The root mean square errors of simulated cutting force components were obtained from taught and untaught data for the various neural networks. Results show that the error trends for untaught data were non-uniform because of the complex nature of the cutting force components, which was caused by different cutting factors and nonlinear characteristics coming into play. However, trends for taught data showed a very good coincidence.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.30 no.1
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• pp.74-81
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• 2007

절삭가공에서 가공조건은 가공비용의 감소와 제품 품질의 향상에 영향을 주는 주요 요인 중의 하나이다. 본 논문에서는 밀링작업을 대상으로 가공조건을 보다 효율적으로 수정하고 이를 지속적으로 향상시킬 수 있는 방법론과 이를 기반으로 개발된 작업설계시스템을 소개한다. 개발된 시스템은 (1) 표준 가공조건을 세부 공정별 요구 사항이 만족되도록 수정하고, (2) 퍼지아트맵 신경회로망 모델을 이용하여, 생성된 가공조건을 온라인(incremental) 학습한 후, (3) 보다 효율적인 새로운 가공조건이 생성되었을 때 이를 교체알고리즘이라 불리는 제안된 알고리즘을 이용하여 기존의 가공조건을 대체하는 3가지 핵심 기능으로 구성된다. 우선 새로운 방법론이 적용된 작업설계시스템의 전반적인 내용을 소개한 후, 다음으로 다양한 시뮬레이션을 통하여 제안된 방법론의 성능을 예시한다. 마지막으로 실제부품에 적용한 실행 결과를 기술하고 토의한다.

• Journal of the Semiconductor & Display Technology
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• v.10 no.3
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• pp.49-52
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• 2011

This paper shows the results of classical molecular dynamics modeling for the interaction between spherical nano abrasive and substrate in chemical mechanical polishing processes. Atomistic modeling was achieved from 3-dimensional molecular dynamics simulations using the Morse potential functions for chemical mechanical polishing. The abrasive dynamics was modeled by three cases, such as slipping, rolling, and rotating. Simulation results showed that the different dynamics of the abrasive results the different features of surfaces. The simulation concerning polishing pad, abrasive particles and the substrate has same results.

• 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.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2019.11a
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• pp.101-103
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• 2019

기존 해상용 등명기의 경우 빛을 평행하게 만들기 위해 볼록렌즈를 정교하게 절삭하여 곡률을 제작하는 기술이 까다로워 해상용 등명기 제작비용이 비싼 프레넬 렌즈를 사용하고 있다. 따라서 프레넬 렌즈를 사용하지 않고 평행 광을 만들 수 있는 포물선 반사체(parabolic reflector)의 원리를 도입하였다. 포물선 반사체의 원리는 포물선 초점에 있는 LED 광원에서 빛을 반사체에 반사하여 평행 광을 만드는 원리이며, 포물선 반사체에 반사된 빛은 45° 기울기의 원뿔형 반사체에 한 번 더 반사되어 지표면과 평행한 빛을 360° 방향으로 균일하게 내보낸다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.20-20
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• 2009

치아의 치석제거 및 치골절삭에 사용되는 초음파 스케일러는 일반적으로 마그넷형과 압전형으로 구분할 수 있으며, 최근에 들어 소형화, 저전력, 정밀성, 저비용 등의 장점으로 인해 압전형이 주로 사용되고 있다. 국내의 대부분의 치과에서 한 대 이상 운용되는 초음파 스케일러는 대부분 유럽 제품으로며, 국내에서는 이를 대체하기 위한 제품이 출시되고 있으나 아직까지 유럽 제품에 비해 출력강도, 정밀도 등에서 성능이 모자란 현실로 시장에서 외면 받고 있다. 본 연구에서는 앞서 언급한 압전 초음파 스케일러에 대한 체계적인 연구를 진행하여 외국에 비해 상대적으로 성능이 떨어지는 초음파 스케일러의 성능을 개선하고자 하였다. 이를 위하여 스케일러의 진동 발생부, 즉 압전 세라믹과 SUS 재질의 head, tail 부로 구성된 진동발생부의 최적구조톨 도출하기 위하여 유한요소 해석을 실시하였으며, 스케일러의 중심주파수 28kHz에서 최대 출력이 발생할 수 있는 구조를 도출하였다. 스케일러의 Head 와 Tail 부문의 두께와 직경, 길이 변화에 따른 중심주파수 및 출력 변위의 경향분석을 실시하였으며, 이상의 결과를 바탕으로 실제 스케일러를 제작하여 시뮬레이션의 유효성을 검증하였다. 이상의 과정으로 거쳐 개발된 압전 초음파 스케일러는 다양한 Tip 종류의 영향을 최소화할 수 있으며, 중심주파수는 28~30kHz 에서 뛰어난 성능을 나타내어 기종 유럽제품의 성능을 앞지르는 특성을 확보할 수 있었다.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.5
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• pp.431-439
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• 2015

One of common challenges in designing modern production machines is realizing high speed motion without sacrificing accuracy. To address this challenge it is necessary to maximize the stiffness of the mechanical structure and the control system with consideration on the main disturbance input, cutting forces. This paper presents analysis technologies for realizing high stiffness in production machines. First, CAE analysis techniques to evaluate the dynamic stiffness of a machine structure and a new method to construct the physical machine model for servo controller simulations are demonstrated. Second, cutting forces generated in milling processes are analyzed to evaluate their effects on the mechatronics system. In the effort to investigate the interaction among the structure, controller, and process, a flexible multi-body dynamics simulation method is implemented on a magnetic bearing stage as an example. The presented technologies can provide better understandings on the mechatronics system and help realizing high stiffness production machines.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.6 s.183
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• pp.151-159
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• 2006

This paper describes a design process of end-milling cutters: solid model of the designed cutter is constructed along with computation of cutter geometry, and the wheel geometry as well as wheel positioning data f3r fabricating end-mills with required cutter geometry is calculated. In the process, the main idea is to use the cutting simulation method by which the machined shape of an end-milling cutter is obtained via Boolean operation between a given grinding wheel and a cylindrical workpiece (raw stock). Major design parameters of a cutter such as rake angle, inner radius can be verified by interrogating the section profile of its solid model. We studied relations between various dimensional parameters and proposed an iterative approach to obtain the required geometry of a grinding wheel and the CL data for machining an end-milling cutter satisfying the design parameters. This research has been implemented on a commercial CAD system by use of the API function programming, and is currently used by a tool maker in Korea. It can eliminate producing a physical prototype during the design stage, and it can be used for virtual cutting test and analysis as well.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.12
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• pp.1700-1706
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• 2016

To improve the number of simultaneous transmissions of machine-to-machine traffic in a spread spectrum ALOHA channel, we propose a new spreading technique called doubly truncated cyclic code shift keying (DTCCSK). By truncating the codeset of cyclic code shift keying, DTCCSK freely adjusts the spreading factor and the symbol length. As a result, DTCCSK exhibits both a high spectral efficiency of M-ary signaling and low implementation complexity of a direct sequence.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.1
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• pp.245-252
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• 2018

In this paper, the dual band circular polarization patch antenna was designed by using band rejection characteristics of CSRR structure for geostationary satellites. A quadrangular CSRR structure was etched on the ground at the rear of the patch antenna's feed to obtain band rejection characteristics in between the receiving frequency band(1525~1559MHz) and transmission band(1626.5~1660.5MHz), and the corner of the patch antenna was truncated to enable circular polarization. It was confirmed that the resonant frequency of the patch antenna differs according to the size anc location of the CSRR and cirular polarization characteristics with simulation and measurement results. Measurement results shows the gain of about 0.2dB and 1.5dB in the TX and RX band.