• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1998년도 춘계학술대회 논문집
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• pp.40-52
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• 1998

Among the non-traditional machining methods, Abrasive waterjet machining process shows big promise in drilling difficult-to-machine materials due to its numerous advantages such as absence of heat affect zone and thermal distortion. Acoustic emission signal technique is used to understand about material removal mechanisms during abrasive waterjet drilling process. More information about the drilling process is derived through frequency decomposition of auto regressive moving average modeling representing acoustic emission signals.

• 한국공작기계학회논문집
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• 제13권1호
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• pp.1-8
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• 2004

Thermal distortion is a critical issue in machine tools, especially in high speed machining. This is the reason why recent machine tools have thermal compensation function. To compensate thermal distortion, it is necessary to make a model that has some relationship between temperature and deformation. Various experimental methods ye widely been used in thermal test: constant spindle speed, unit step speed increase, random spindle speed, etc. This paper focuses on which type of spindle operation condition is good for thermal experiment. Also, experimental data is modeled using multiple linear regression models and compared each other to select a method. Consequently, it turned out at e condition of 75％ constant of maximum spindle speed is good enough to generate temperature and distortion data.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1992년도 추계학술대회 논문집
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• pp.136-144
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• 1992

Recently, Silicon Nitrde ceramic is regarded as the representative engineering ceramic with the excellent mechanical properties and many functions for mechanical components and parts among various kinds of ceramics in the mechanical industry. But, during the manufacturing of engineering ceramics, there is many volumetric shrinkage coupled with a distortion of the parts which is produced. Due to the requirement for high accuracy of size, form, and surface finish of the components, machining is needed surely. Nowdays, grinding with a resin bond type diamond wheels has been generally applied to machining of the engineering ceramics in the whole world because that it can be conveniently proceeded for workers to dress of tool and made with high reliability in producing factories among many bond type super-abrasive wheels yet. It is important task for attaining prescribed mechanical components with high reliability to observe the grinding mechanism of ceramics as like generation of cracks and chipping of material during process. Because they considerably effects on the strength characteristic of machined mechanical components. In this study, various surface grinding experiments using resin bond type diamond wheels are carried out for Silicon Nitride ceramic. Grinding mechanism of ceramics is observed experimentally and the relationship with various conditions is also attained. Form this experimental study, some useful machining data and information to determine proper machining condition for grinding of Silicon Nitride ceramic is obtained.

• 한국생산제조학회지
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• 제7권5호
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• pp.15-28
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• 1998

Recently may investigations have been studied on the high-speed machining by using machine tools. A CNC machine tool makes some tool path errors caused by software acceleration/deceleration. The faster a cutting feedrate is, the bigger the tool path errors are. Some known methods reduce these kinds of errors, but they make the total cutting time increased. This paper presents a feed-forward algorithm that can be generated by distorting the original tool path, and reduces the tool path errors and the total cutting time. The algorithm to generate a new tool path is represented as following; 1)calculating each distance of software acceleration/deceleration between two adjacent blocks, 2) estimating the distorted distance which is the adjacent-ratio-constant(k1, k2) multiply the distance of software acceleration/deceleration, 3) generating a 3-degree Bezier curve approximating the distorted tool path, 4) symmetrically transforming the Bezier curve about the intersection point between two blocks, and 5) connecting the transformed Bezier curve with the original tool path. The algorithm is applied to FANUC 0M. The study is to promote the high-precision machining and to reduce the total cutting time.

• 전기전자학회논문지
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• 제23권1호
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• pp.22-28
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• 2019

본 연구는 차량용 보링 생산 공정에서 기계적인 에러를 체크하기 위한 품질 체크용 모니터링 시스템을 개발한다. 기계적인 에러는 이상적인 절단경로와 비교하여 실제 절단경로의 공간위치 차이에서 나타난다. 제조공정 제품의 오차를 모니터하기 위해 제품의 인지왜곡, 죄임 에러, 기계공구의 회전과 운동에러의 반경회전과 같이 보링 품질에 영향을 미치는 다수 요소들을 설명한다. 생산품질을 입증하기 위해 IT 융합에 기반한 공정 에러율을 분석하고 분석 데이터를 메모리에 저장하는 품질체크 방법을 제안한다. 따라서 불량 생산 제품을 감지함으로써, 생산 코스트와 베어링의 손실을 줄일 수 있다.

• Design & Manufacturing
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• 제15권3호
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• pp.32-38
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• 2021

Plate-shaped works are one of the materials that can be applied to the entire industry due to their various shapes and sizes. Plate-shaped parts workpieces are thin and wide, and when processing is completed, they are often bent or deformed in various directions, making it difficult to produce normal products. In particular, this study intends to study the processing deformation and distortion of plate-shaped parts fastened to the jig during milling processing. In this study, a method for preventing deformation occurring in plate-shaped parts was derived through jig element change and CAE analysis, and this was applied to actual processing to produce products with stable dimensions. Through a finite element analysis experiment, it was found that installing two supports on the back of the plate-shaped part results in minimal deformation and the optimal distance between the two supports is 150 mm. Through this experiment, when processing a thin plate product, a support was installed in a direction opposite to the cutting force applied to the thin plate to prevent deformation of the product, thereby improving defects.

• 소성∙가공
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• 제22권6호
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• pp.323-327
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• 2013

In this paper, the flow lines as a function of product design as well as the forging process design are explored using typical application examples. The prediction of flow lines using metal forming simulation technology is introduced along with their characterization. Experimental studies have shown that the metal flow lines have a strong influence on the structural rigidity of the final product. In this study we present several typical applications. One example is the case of severely cut metal flow lines during machining, especially in the region where periodic contacting forces are applied. Another example is the case of abnormal distortion of flow lines which can cause too much elongation or hot shortness due to viscous heating in the region of distortion. A third example is the case of a macrosegregation region which needs to be controlled so it is not adjacent to the region where the force is applied in the use of the final component. An example of weight reduction for an automobile component with improved flow lines is also introduced. These typical applications can provide process engineers with the insight in designing automobile or mechanical components as well as in designing the manufacturing methods to produce various parts.

• 디지털융복합연구
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• 제10권10호
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• pp.301-306
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• 2012

본 논문은 머신비전시스템에서 정확한 이미지 획득을 위한 방법을 제안한다. 각종 렌즈에서 요구되는 가장 중요한 기능으로는 실물과 동일한 고품질의 결상을 구현하는 광학적 역할이다. 그러나 머신비전시스템의 입력부에서는 렌즈의 수차로 인하여 왜곡현상이 발생한다. 이러한 문제를 해결하기 위해 실세계 좌표계와 영상 좌표계 간의 변환 관계를 정의해주는 매핑 기능으로, 행렬연산을 통하여 두 좌표간의 거리를 계산하여 정확한 위치를 지정하게 된다. 레이저 정밀 가공작업에서도 Galvanometer를 사용하면 비구면 초점 렌즈에 의하여 발생되고 있는 렌즈 수차를 보정하여야 가공 오차를 개선 할 수 있다. 비구면 렌즈의 수차는 2차원 곡선의 형태를 가지고 있으나, 기존의 렌즈 보정 방법인 선형방법은 매우 많은 점들을 검사하여 보정시간이 많이 소요되는 문제점이 있었다. 가공장비에서 렌즈의 수차로 인하여 발생하는 가공오차를 감소시키기 위하여 Bilinear interpolation 기법을 적용하는 방법을 제안하였다. 제안한 방법은 기존 선형방법과 비교하여 위치 오차의 평균값과 표준편차가 향상되었음 실험을 통하여 입증하였으며 실제 레이저 응용업무에 적용하고 있다.

• 한국산학기술학회논문지
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• 제20권1호
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• pp.290-296
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• 2019

차량용 HUD는 자동차 전면 유리창에 안전 운전과 편의 운전 관련 다양한 정보를 표시해 주는 장치로 중요한 역할을 수행한다. 본 논문에서는 증강현실 기술에 적용이 가능한 대면적 비구면 자유형상 미러를 가공하기 위해 초정밀 가공기를 이용하여 가공을 실시하였고 그 결과를 측정하였다. 초정밀 다이아몬드 절삭은 정밀도가 높을 뿐만 아니라 표면 거칠기와 잔류 응력을 낮게 할 수 있어서 우수한 표면 무결성을 갖는 고급 부품의 생산에 유리하다. 또한 비구면 자유 형상의 몰드를 사용함으로써 광학 전달 함수의 개선, 왜곡 경로의 감소 및 특수 이미지 필드 곡률의 실현과 같은 장점을 얻을 수 있다. 이와 같은 비구면 자유형상 금형을 가공하기 위한 방법으로는 초정밀가공기를 이용한 다이아몬드 절삭 방법을 사용하였으며, 제작된 비구면 자유형상 미러 금형의 평가는 비구면 형상 측정기를 이용하여 실시하였다. 이러한 방법에 의해 $1{\mu}m$ 이하의 형상 정밀도(PV)와 $0.02{\mu}m$ 이하의 표면 거칠기(Ra)를 갖는 비구면 자유형상 금형을 제작할 수 있었다.

• 한국정밀공학회지
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• 제15권7호
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• pp.7-17
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• 1998

Stereolithography is a process used to rapidly produce stereolithographic parts directly from three dimensional CAD models. However design methodologies to create components to be built by stereolithography are different from those required by conventional machining processes. As a typical case in point, the support structures are required to support a component at build stage, but are later removed once building and curing are complete. These structures are used to anchor the component to the platform and to prevent sagging or distortion. This paper deals with the Support Map data structure prepared to find the appropriate regions of supports. Interferences between supports and parts, and support structure themselves as well, are checked and thus the system are searching the statically stable regions to remove the surplus support structures. Cross shaped tooth profiles are designed for easy eliminating the support structures.