• 한국정밀공학회지
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• 제32권3호
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• pp.243-251
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• 2015

In order to develop an automatic system for welding thin steel plates with curvature such as the corrugated membranes of an LNG storage tank, a rotating mechanism should be firstly designed for the torch to easily follow the weld seam with a constant distance and angle. In this study, a torch rotating mechanism consisting of three circular links, two square-type links and a torch link was proposed for automation of the welding process. A weld-seam tracking system with two axis slides and the proposed rotating mechanism was successfully simulated with a dynamic simulation software. A prototype tracking system was manufactured and a tracking test with the system was then carried out. The test results with tracking system showed that the rotating mechanism could be implemented and it was feasible to be used in automatic tracking of weld seam with curvature.

• 대한기계학회논문집
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• 제18권11호
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• pp.3057-3065
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• 1994

An experimental study has been made for heat transfer and particle deposition during the Modified Chemical Vapor Deposition process which is currently utilized to manufacture high quality optical waveguides. The distributions of tube wall temperatures, rates and efficiencies of particle deposition were measured. Results indicate that the temperature distributions of the tube wall in the axial direction yield the quasi-steady form in which temperature distributions fit in one curve if the relative distance from the moving torch is used as an axial coordinate. Due to the repeated heatings from the traversing torch, the wall temperatures are shown to reach the minimum ahead of torch and it is shown that the two torch formulation suggested by Park and Choi is valid to predict this minimum temperature. Measured wall temperatures, particle deposition efficiencies and tapered entry length are compared with the previous modelling results and shown to be in agreement.

• 한국산학기술학회논문지
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• 제14권4호
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• pp.2021-2026
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• 2013

냉각법은 용접과 동시에 용접토치로 부터 일정한 거리 떨어져 있는 용접부를 냉각기체를 이용하여 냉각시켜 용접변형을 최소화시키는 기술이다. 냉각기체에 의해 용접부의 온도를 감소시키면 용접부에 발생하는 열응력이 감소되고 그 결과 소성변형이 최소화되어 최종적으로 용접좌굴과 각변형을 방지할 수 있는 기술이다. 이 방법은 용접부 표면을 냉각시키는 방법으로 용접부를 직접 냉각시킴으로서 현장 적용성 면에서 다른 용접변형 방지법 보다 효율적이다. 본 연구에서는 맞대기용접을 대상으로 용접 후면의 냉각조건(폭, 길이)을 변화시켜 열탄소성해석을 실시하여 해석적방법으로 용접 각변형에 미치는 영향을 검토하였다. 그 결과 용접토치와 냉각 선단과의 거리는 25mm, 냉각 길이는 80mm, 냉각 폭은 30mm의 경우가 각변형 저감에 제일 큰 효과가 있었다. 이때 냉각길이는 길면 길수록 각변형을 감소시킨다.

• Journal of Welding and Joining
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• 제34권6호
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• pp.20-27
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• 2016

This study deals with the proper conditions of the trail rolling method (TRM) for the prevention of the buckling welding distortion at the AA5083 GMA butt weldment. For it, the effect of the working conditions of TRM including the rolling depth and the rolling distance between the welding torch and the roller on the longitudinal welding shrinkage force of the weldment was evaluated by using 3 dimensional thermo-mechanical FE analyses. The longitudinal welding shrinkage force inducing the buckling welding distortion at the GMA butt weldment was mitigated with an increase in the rolling depth and the rolling distance between the welding torch and the roller. Based on the results, the proper conditions of trail rolling method were established to reduce the longitudinal welding shrinkage force of the GMA butt weldment to below the critical value corresponding to the bucking distortion.

• Journal of Welding and Joining
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• 제16권5호
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• pp.119-133
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• 1998

To implement full automation in pipe welding, it si most important to develop special sensors and their related systems which act like human operator when detecting irregular groove conditions. In this study, an automatic pipe Gas Metal Arc Welding (GMAW) system was proposed to full control pipe welding procedure with intelligent sensor systems. A five-axes manipulator was proposed for welding torch to automatically access to exact welding position when pipe size and welding angle were given. Pool status and torch position were measured by using a weld-pool image monitoring and processing technique in root-pass welding for weld seam tracking and weld pool control. To overcome the intensive arc light, pool image was captured at the instance of short circuit of welding power loop. Captured image was processed to determine weld pool shape. For weld seam tracking, the relative distance of a torch position from the pool center was calculated in the extracted pool shape to move torch just onto the groove center. To control penetration of root pas, gap was calculated in the extracted pool image, and then weld conditions were controlled for obtaining appropriate penetration. welding speed was determined with a fuzzy logic, and welding current and voltage were determined from a data base to correspond to the gap. For automatic fill-pass welding, the function of human operator of real time weld seam control can be substituted by a sensor system. In this study, an arc sensor system was proposed based on a fuzzy control logic. Using the proposed automatic system, root-pass welding of pipe which had gap variation was assured to be appropriately controlled in welding conditions and in torch position by showing sound welding result and good seam tracking capability. Fill-pass welding by the proposed system also showed very successful result by tracking along the offset welding line without any control of human operator.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2011년도 후기공동학술대회 논문집
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• pp.91-91
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• 2011

• 한국산학기술학회논문지
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• 제14권3호
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• pp.1016-1021
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• 2013

수소혼합가스토치를 이용하여 유리 모서리 접합 시 접합부의 형상은 수소혼합가스의 유량, 토치의 이송속도, 토치와 유리사이의 거리 등 많은 공정변수들에 의해 영향을 받는다. 모서리 접합형상은 유리패널의 단열 및 기밀, 강도성능에 영향을 미치므로, 공정변수에 따른 접합부 형상예측에 대한 연구가 수행되어야 한다. 따라서 본 논문에서는 공정변수 설정 및 실험분석을 통하여, 공정변수에 따른 단면형상을 예측할 수 있는 회귀식을 도출하였다. 도출된 회귀식에 각 공정변수값을 적용하여 접합형상을 예측하고, 실제 모서리 접합 실험결과와 비교하여 회귀식의 타당성을 검증하였다.

• 한국정밀공학회지
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• 제17권7호
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• pp.132-140
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• 2000

Plasma arc cutting is one of the most widely used processes in metal cutting fields and is a process that produces parted metal plates by cutting them with an arc plasma established between the electrode tip and the plate(workpiece). When the tip-to-workpiece distance varies during cutting, the cut quality, for example the kerf width, is deteriorated by the change of plasma arc. The variations of tip-to-workpiece distance are due to the different factors such as inaccuracies in setting the torch or workpiece, thermal distortions during cutting, and uneven surface of workpiece. The control to keep the tip-to-workpiece distance constant is thus indispensable to improve the flexibility of automatic plasma arc cutting system applications. In this study, an arc sensor which utilizes the electrical signal obtained from the plasma arc itself was developed. The arc sensor has an advantage that no particular sensing device is necessary and real-time sensing of the tip-to-workpiece distance is possible directly under the plasma arc. The relationship between plasma arc voltage and tip-to-workpiece distance was determined through the repeated experimental results. The model was used for developing an automatic tip-to-workpiece distance control system of plasma arc cutting. It could be shown that the proposed system has a successful capability of tip-to-workpiece distance control.

• 분석과학
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• 제25권5호
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• pp.265-272
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• 2012

기존의 Okamoto cavity를 변형시킨 WR-340 도파관을 사용한 cavity를 제작하고 고출력(2.45 GHz, 2 kW)의 헬륨, 질소 및 아르곤 마이크로파 플라즈마(MIP; Microwave Induced Plasma)를 성공적으로 형성시켰다. 플라즈마 생성의 주요한 요인들은 내부전도체의 직경과 내부전도체와 외부전도체간의 간격, 내부전도체 끝과 토치의 위치 등이 있으며 그 중 헬륨 마이크로파 플라즈마에 대하여 cavity의 디자인을 최적화시키고 그 특성을 조사하였다. ICP(Inductively Coupled Plasma)용 mini 토치와 자체 제작한 나선형흐름토치를 비교 연구한 결과, 헬륨 플라즈마 기체 흐름량은 약 25 L/min~30 L/min로서 서로 비슷하였다. 토치 상단부에 석영관을 덧씌워 공기유입을 막은 결과, 340 nm 근처의 NH분자선들이 없어지거나 감소하였다. 플라즈마의 온도 및 전자밀도를 측정한 결과, 4,350 K의 들뜸 온도와 $3.67{\times}10^{11}/cm^3$의 전자밀도를 얻었다. 이 값들은 기존의 다른 마이크로파 플라즈마와 비슷하거나 약간 작은 값이다. 고출력의 플라즈마로서 수용액을 직접 분석하는 것이 가능하였고 현재 Cl의 검출한계는 116 mg/L 수준으로서 아직 분석적인 최적화가 필요한 단계이다.

• 대한기계학회논문집A
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• 제35권11호
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• pp.1491-1497
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• 2011

용접 장치 설계 시 고려해야 할 중요한 요소 중의 하나는 용접 궤적과 토치의 간격 오차를 줄이는 것이다. 특히 원호와 직선이 결합된 용접 궤적의 경우는 변곡점에서 오차의 영향이 크게 작용한다. 본 연구의 대상은 선체 블록 내부 탱크와 탱크 사이의 유체(물, 기름 등) 이동을 방지하기 위하여 설치되는 커버플레이트(Cover Plate) 용접으로서, 커버플레이트 원호용접은 위보기, 수직, 아래보기의 3 가지 자세를 동시에 포함한다. 본 연구는 작업 궤적의 각 구간 사이에서 발생하는 토치의 궤적 오차를 최소화할 수 있는 2 축 소형 용접 장치 개발에 관한 것으로서, 원호와 직선 부 사이의 변곡점에서 발생하는 토치 궤적 오차를 최소화하기 위한 구동 메커니즘 도출 과정에 대하여 기술하였다.