• 한국기계가공학회지
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• 제19권11호
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• pp.64-69
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• 2020

To determine the effective factors for microparticle blasting with precise sequence position control in the x-axis and y-axis directions, we conducted a statistical experimental analysis of blasted square shapes by considering five condition factors. The control input and output were operated simultaneously by rotation-linear motion conversion and fine particles were blasted onto the aluminum specimen by precise position control driving using multiple execution codes. The micro-driving device used for processing was capable of microparticle blasting and of controlling the system through contact with a limit sensor at high speed and a two-degree-of-freedom driving mechanism. Our experiments were conducted on 1,050 specimens of pure aluminum (containing <1% of other elements). The effects of several factors (e.g., particle and nozzle diameters, blasting pressure, and federate and blasting cycle numbers) on the surface roughness and blasted surface's depth were verified through a statistical experimental analysis by applying the dispersion analysis method. This statistical analysis revealed that the nozzle diameter, the blasting pressure, and the blasting cycle number were the dominant factors.

• 한국기계가공학회지
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• 제20권6호
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• pp.10-16
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• 2021

Drilling is a crucial process that takes up a significant amount of weight during machining operations. In addition, drill tip-type tools and related operations have been developed for manufacturing industries to achieve economic efficiency. In this study, SM45C carbon steel, widely used for machine structures, was utilized as the working material after quenching and tempering. Insert-tip types of carbide tools, such as TiN and TiAlN, were used as tool materials. Drilling conditions such as the spindle revolution, feed rate, step of cut, and tool diameter were used to measure roughness, roundness, and straightness using the orthogonal array table statistical method. The surface roughness, roundness, and straightness characteristics based on the conditions were analyzed using ANOVA. The results showed that the spindle speed and feed rate were the main factors influencing carbide insert-tip drilling under the same conditions as the experimental conditions.

• 대한치과보철학회지
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• 제42권3호
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• pp.307-326
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• 2004

Statement of problem. The long-term success of implants is the development of a stable direct connection between bone and implant surface, which must be structural and functional. To improve a direct implant fixation to the bone, various strategies have been developed focusing on the surface of materials. Among them, altering the surface properties can modify cellular responses such as cell adhesion, cell motility and bone deposition. Purpose. This study was to evaluate the cellular behaviors on the surface-modified titanium by morphological observation, cellular proliferation and differentiation. Material and methods. Specimens were divided into five groups, depending on their surface treatment: electropolishing(EP) anoclizing(AN), machining(MA), blasting with hydroxyapatite particle(RBM) and electrical discharge machining(EDM). Physicochemical properties and microstructures of the specimens were examined and the responses of osteoblast-like cells were investigated. The microtopography of specimens was observed by scanning electron microscopy(SEM). Surface roughness was measured by a three-dimensional roughness measuring system. The microstructure was analyzed by X-ray diffractometer(XRD) and scanning auger electron microscopy(AES). To evaluate cellular responses to modified titanium surfaces, osteoblasts isolated from neonatal rat were cultured. The cellular morphology and total protein amounts of osteoblast-like cell were taken as the marker for cellular proliferation, while the expression of alkaline phosphatase was used as the early differentiation marker for osteoblast. In addition, the type I collagen production was determined to be a reliable indicator of bone matrix synthesis. Results. 1. Each prepared specimen showed specific microtopography at SEM examination. The RBM group had a rough and irregular pattern with reticulated appearance. The EDM-treated surface had evident cracks and was heterogeneous consisting of broad sheet or plate with smooth edges and clusters of small grains, deep pores or craters. 2. Surface roughness values were, from the lowest to the highest, electropolished group, anodized group, machined group, RBM group and EDM group. 3. All groups showed amorphous structures. Especially anodized group was found to have increased surface oxide thickness and EDM group had titaniumcarbide(TiC) structure. 4. Cells on electropolished, anodized and machined surfaces developed flattened cell shape and cells on RBM appeared spherical and EDM showed both. After 14 days, the cells cultured from all groups were formed to be confluent and exhibited multilayer proliferation, often overlapped or stratified. 5. Total protein amounts were formed to be quite similar among all the group at 48 hours. At 14 days, the electropolished group and the anodized group induced more total protein amount than the RBM group(P<.05). 6. There was no significant difference among five groups for alkaline phosphatase(ALP) activity at 48 hours. The AN group showed significantly higher ALP activity than any other groups at 14 days(P<.05). 7. All the groups showed similar collagen synthesis except the EDM group. The amount of collagen on the electropolished and anodized surfaces were higher than that on the EDM surface(P<.05).

• 한국기계가공학회지
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• 제7권2호
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• pp.52-59
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• 2008

The objective of this study is to develop an automatic object changer unit to improve processing problems existed in the conventional horizontal machining center. To achieve this goal, this study designed a horizontal transfer as the second project continued to the first project that designed a upward and downward traverse unit. A horizontal traverse unit shows a symmetric structure and consists of frame, which consists of four unit tools, motor and reducer, which are fixed at a frame, operation unit with pinions, first traverse unit, and second traverse unit. Constraint conditions based on the operation mechanism with these elements were configured and obtained following results after modeling a model for a traverse motor. In the kinematic expression of sliding motion with one degree of freedom, the sliding motion is constrained. Also, the rack 3 installed at a frame is used to configure possible kinematic constraint conditions of the rack 2 according to the rolling motion of the pinion 2 in the first traverse unit. In addition, the moment of inertia that is a type of kinetic energy in a converted horizontal traverse unit in the side of the reducer can be applied to introduce the moment of inertia of a converted horizontal traverse unit in the side of the reducer by using the sum of kinetic energy in the rack and pinion, which is a part of the horizontal traverse unit. Also, the equation of motion of the converted upward and downward traverse unit in the side of the motor using the equation of motion of the motor. Furthermore, the horizontal traverse unit predetermines the mass of the first and second traverse unit and applied load including the radius and reduction ratio of the pitch circle in the pinion 1 and applied load to the rack 2. Then, a proper motor can be determined using several parameters in the upward and downward traverse unit in order to verify such predetermined specifications. In future studies later this study, a simulation that verifies the results of the previous two stages of studies using a finite element method.

• 대한공업교육학회지
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• 제33권2호
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• pp.259-272
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• 2008

목형의 곡면을 수작업으로 제작할 때 많은 경험이 있다 하더라도 정확한 곡면 형상, 좌우대칭 등의 작업에는 상당한 어려움이 따른다. 기계를 사용한 단순한 2차원 목형은 NC 프로그램을 작성하여 간단히 가공할 수 있지만, 복잡한 곡면 형상의 가공은 3차원 CAM s/w, 공구, 재료 등 다양한 변수가 따르기에 축척된 많은 데이터를 필요로 한다. 3차원 곡면 가공 제품 중 제품의 설계 및 디자인 s/w가 다르다면, 데이터의 호환 및 가공 시스템을 구성하기에는 더더욱 어려움이 따른다. 최근 레저에 대한 관심이 증가함에 따라 레저보트 업체에서는 수작업 대신 레저장비에 대한 소비자의 디자인 및 설계제작 요구에 대응하기 위해서 가공 자동화 및 정밀도 향상을 위하여 CAD/CAM 시스템을 이용한 3차원 모델링 및 CNC 공작기계를 사용한 새로운 개념의 플러그 제작 자동화 기술 개발이 필요하게 되었다. 따라서 본 연구는 수작업으로 제작하던 레저보트의 목형을 정밀도와 생산성 향상을 위하여 디자인을 강조한 3차원 디자인 s/w로 디자인하고, 이 디자인 한 데이터를 이용하여 3차원 CAM s/w에서 모델링 한 후, 가공 데이터를 산출하여 정밀가공기계인 머시닝센터로 가공하고자 하는 것이다. 이 연구 결과를 바탕으로 전문계 고교에서도 CAD 및 단순 가공 기술교육에서 벗어나 다양한 디자인으로 된 곡면 가공 수요자의 요구에 대응하기 위한 3차원 모델링과 3차원 정밀 가공 시스템의 교육 및 개발에 도움이 되었으면 한다. 본 연구는 선박의 하단부인 헐(Hull)의 목형인 플러그(plug)를 가공하기 위하여 플러그의 재료, 2차원 도면 형상을 3차원 형상으로의 모델링, 3차원 디자인 모델링, 가공을 위한 CAM, CNC 공작기계를 이용한 가공 기술 등 여러 가지 융합되고 복합적인 기술인 CAD/CAM 시스템을 활용한 모델링 및 플러그 가공 기술을 개발하는 것이다. 학생들에게는 기술개발의 중요성을, 업체에게는 생산성 향상이 주목적이다.

• 대한의용생체공학회:의공학회지
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• 제23권3호
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• pp.217-225
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• 2002

이식형 인공중이는 일반적인 공기전도형 보청기가 가지는 난점인 고이득에서의 왜곡과 음향 피이드백에 의한 링잉 현상을 해결할 수 있는 동시에 음질과 주파수 특성 및 청음명료도가 우수하다 본 논문에서는 마이크로머시닝 기술을 이용하여 차동 전자 트랜스듀서를 제작한 후 이를 사용하여 이식형 인공중이 시스템을 구현하였다. 제작된 시스템을 이용하여 무부하 진동실험. 사체를 이용한 부하진동실험 및 살아있는 개를 이용하여 동물이식실험을 실시함으로써 이의 성능을 확인하였다. 무부하 진동실험을 통하여 제작된 트랜스듀서는 입력되는 소리신호와 같은 형태의 진동을 일으킴을 확인하였고, 사체의 이소골에 트랜스듀서를 이식하고 부하실험을 실시함으로써 트랜스듀서의 이소골 구동능력과 진동특성을 조사하였다. 그리고 개를 이용하여 동물이식실험을 실시한 후 뇌간 유발 반응검사를 실시함으로써 생체 내에서의 이식형 인공중이의 동작을 확인하였다. 이를 통하여 제작된 차동 전자 트랜스듀서를 이용한 이식형 인공중이 시스템의 성능을 검증하였고 난청자에게 적용할 경우에도 잘 동작할 수 있음을 증명함으로써 임상실험을 실시할 수 있는 근거를 마련하였다.

• 천문학논총
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• 제32권1호
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• pp.359-361
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• 2017

We report our research on aluminum mirror optics for future infrared astronomical satellites. For space infrared missions, cooling the whole instrument is crucial to suppress the infrared background and detector noise. In this aspect, aluminum is appropriate for cryogenic optics, because the same material can be used for the whole structure of the instrument including optical components thanks to its excellent machinability, which helps to mitigate optical misalignment at low temperatures. We have fabricated aluminum mirrors with ultra-precision machining and measured the wave front errors (WFEs) of the mirrors with a Fizeau interferometer. Based on the power spectral densities of the WFEs, we confirmed that the surface accuracy of all the mirrors satisfied the requirements for the SPICA Coronagraph Instrument. We then integrated the mirrors into an optical system, and examined the image quality of the system with an optical laser. As a result, the total WFE is estimated to be 33 nm (rms) from the Strehl ratio. This is consistent with the WFEs estimated from the measurement of the individual mirrors.

• Journal of Electrical Engineering and Technology
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• 제6권2호
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• pp.263-269
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• 2011

In this study, the compositions for the microwave dielectric materials were investigated to obtain the improved dielectric properties, the high temperature stability, and the sintering temperature of less than $900^{\circ}C$, which was necessary for cofiring with the internal conductor of silver. In addition, the dielectric sheets were prepared by the tape casting technique, after which the sheets were laminated and sintered. In this process, the optimum ratio of powder and binder, laminating pressure, temperature, and possibility for cofiring with the internal conductor were studied. Finally, multilayer chip treplexer filter for the 800-2,000 MHz range were fabricated, and the frequency characteristics of the triplexer filter were investigated. When the $0.6TiTe_3O_8-0.4MgTiO_3+3wt%SnO+7wt%H_3BO_3$ ceramics were sintered at $820^{\circ}C$ for 0.3 hours, the microwave dielectric properties of the dielectric constant of 29.91, quality factor of 33,000 GHz, and temperature coefficient of resonant frequency of -2.76 ppm/$^{\circ}C$ were obtained. Using the Advanced Design System (ADS) and High Frequency Structure Simulator (HFSS), the multilayer chip triplexer filter acting at the range of 800-2,000 MHz were simulated and manufactured. The manufactured triplexer filter had the excellent frequency properties in the CDAM800, GPS and PCS frequency regions, respectively.

• Design & Manufacturing
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• 제14권2호
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• pp.14-20
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• 2020

In OLED panel production process, it is necessary to cut a part of protective film as a preprocess for lighting inspection. The current method is to recognize only the fiducial mark of the cut-out panel. Bare Glass Cutting does not compensate for machining cumulative tolerances. Even though process defects still occur, it is necessary to develop technology to solve this problem because only the Align Mark of the panel that has already been cut is used as the reference point for alignment. There is a lot of defective lighting during panel lighting test because the correct protective film is not cut on the panel power and signal application pad position. In laser cutting process to remove the polarizing film / protective film / TSP film of OLED panel, laser processing is not performed immediately after the panel alignment based on the alignment mark only. Therefore, in this paper, we performed real time inspection which minimizes the mechanism tolerance by correcting the laser cutting path of the protective film in real time using Machine Vision. We have studied calibration algorithm of Vision Software coordinate system and real image coordinate system to minimize inspection resolution and position detection error and edge detection algorithm to accurately measure edge of panel.

• 한국산학기술학회논문지
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• 제10권10호
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• pp.2596-2601
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• 2009

후판의 맞대기 용접 시 용접부의 이면에 홈을 파는 가우징 작업은 숙련된 용접 작업과 그라인딩 작업을 필요로 한다. 기존의 가우징은 산소 아크 용접기를 이용하여 제거하고자 하는 부분을 용융시킨 뒤 고압 산소로 불어내는 방식으로 제거된 분진이 작업환경을 열악하게 하며 제거된 부분을 다시 그라인딩 작업으로 평탄화하는 후처리 작업이 필요하기 때문에 생산성을 크게 떨어뜨리고 있다. 이를 절삭에 의한 기계적 제거 작업으로 바꾸어 기존 용접법에 의한 가우징 작업의 단점을 보완하고 생산성을 향상시키고자 절삭 가우징 장치를 개발하고 실험하였다. 개발된 절삭 가우징 장치는 분당 재료제거량이 $13,565mm^3/min$으로 기존 용접법에 의한 가우징에 비해 작업효율이 약 3배 개선되었다. 또한 가공인건비가 1/3 수준으로 감소되는 것을 기대할 수 있으며 소음과 분진으로 인한 작업환경문제가 크게 개선됨을 확인하였다.