• Journal of the Korean Society for Precision Engineering
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• v.17 no.4
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• pp.69-80
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• 2000

Generally, die polishing is a lime consuming process, resulting in 30∼50％ of the whole die manufacturing time. However, die polishing has not been automated yet, since it needs a great deal of experience and skill. This paper describes a new development of automated system for die polishing and focuses on the successful achievements of the element techniques to realize from hand skill to automation, as followings: (1) The 5 axes polishing system by the aid of robot with 2 degrees of freedom, is developed for the application of curved surface die. (2) The CAM system realizes a 5 axes tool path control for polishing and measuring. (3) The conductive elastic tool is able to meet curved surfaces of die and gives a high efficient and quality polishing characteristics. (4) The surface roughness measurement device with noncontact laser is developed and has a high reliability without surface damage.

• Transactions of Materials Processing
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• v.20 no.3
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• pp.206-213
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• 2011

A flexible die, which is composed of a number of punches with adjusted heights to form a three-dimensional curved surface, is a crucial part of a flexible forming technology. In this study, the punch and control system of the flexible die were designed. The flexible die is divided into three modules, namely, punch, control and joint, and the corresponding modules were developed. The punch module materializes a three-dimensional forming surface by the control module, which is composed of an AC servo motor set and a linear guide. The joint module is necessary for the sequential motion between the servo motor set and the punch module. A sequential motion algorithm for the AC servo motor set, that uses the data of the punch relative heights, was also proposed. Finally, a flexible stretch forming test was carried out using the presently designed flexible die.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.359-362
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• 2003

The bending phenomenon has been known to be occurred by the different of velocity at the die exit. The difference of velocity at the die exit section can be obtained by the different velocity of billets through the multi-hole container and by the cohesion of billet inside the porthole die chamber. The bending phenomenon can be controlled by the different hole diameter. The experiments using aluminium material for the curved tube product had been done. The results of the experiment show that the curved tube product can be formed by the extru-bending process without the defects such as the distortion of section and the thickness change of the wall of tube and the folding and wrinkling. It is known that the welding and extruding of each billet has done simultaneously although the curved tube is extruded with four billets.

• Journal of Ocean Engineering and Technology
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• v.16 no.2
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• pp.38-43
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• 2002

Die-less forming is a cold forming process which is to bend thick flat plates into compound curved plates using two asymmetric rollers. This forming method has several advantages compared with line heating which is widely used to fabricate compound curved pieces in shipyards. The die-less forming, however, has scarcely been studied. Even the deformation mechanism in this forming process has not been understood clearly. So, in this paper, the deformation characteristics of die-less forming is investigated analytically and numerically. for the analytic investigation, slab method based on equilibrium equation is applied. And the mechanism of curvature generation is derived for the asymmetry in roller applied. And three dimensional numerical analyses are performed with realistic modeling of interactions between the rollers and work-piece using finite element program, ABAQUS. It is shown that curvature generation is mainly due to the difference of normal positive strain distribution between the top and bottom surface of the work-piece. And a convex-type curved plate is formed if the center region of the work-piece is rolled with asymmetric rollers of which the lower is larger than the upper in diameter.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.114-117
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• 2008

Curved thick plate forming in shipbuilding industry is currently performed by a thermal process, called as Line Heating by using gas flame torches. It was examined as an alternative way in this study to manufacture curved thick plates by the multi-punch die forming. Experiments and finite element analyses were conducted to evaluate the feasibility of the reconfigurable discrete die forming to the thick plates. Configuration of the multi-punch dies suitable for multi-curvature was investigated. As a result, single step forming by reconfigurable discrete die with scale factor improved formability.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.6
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• pp.96-102
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• 2000

The finishing process for dies and molds is an important process because it has influence on final quality of products. And it is difficult to automatize finishing process so that the process has depended on expert's skill until now. However, recently a study on development of die automatic finishing machine has been progressed, and actually this machine is applied to fabrication of die. But the research about tooling system is not enough and finishing tool must have high machining efficiency and adaptability of curved surface. So, this study investigated the application of conductive elastic tool which is composed of metal-resin bonded pellet and elastic backing material. The metal-resin bonded pellet is used to finish the surface by conventional mechanical grinding or electro-chemial grinding method. And elastic backing material is used to follow the curved surface. So conductive elastic tool has long lifetime, uniform removal rate and adaptability of curved surface.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.1312-1315
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• 1996

Polishing work for a curved surface die demands simple and repetitive operations and requires much time while it also demands high precision. Therefore it is operated by skilled worker in handiwork. But workers avoid polishing work gradually because of the poor environments such as dust and noise. In order to reduce the polishing time and to alleviate the problem of shortage of skilled workers, researches for automation of polishing have been pursued in the developed countries such as Japan. In this research we develop a polishing robot with 2 degrees of freedom motion and pneumatic system, and attach it to machining center with 3 degrees of freedom to form an automatic polishing system which keeps the polishing tool vertically on the surface of die and maintains constant pneumatic pressure. The developed polishing robot is controlled by real time sliding mode control using DSP(digital signal processor). A synchronization between machining center and polishing robot is accomplished by using M code of machining center. A performance experiment for polishing work is executed by the developed polishing robot.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.743-747
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• 1997

Polishing work for a curved surface die demands simple and repetitive operations and requires much time while it also demands high precision. Therefore it is operated by skilled worker in handiwork. Howener workers avoid polishing work gradually because of the poor environments such as dust and noise. In order to reduce the polishing time and to alleviate the problem of shortage of skilled workers, researches for automation of polishing have been pursued in the developed countries. In the research, a polishing robot with 2 degrees of freedom motion attached to machining center with 3 degrees of freedom and pneumatic system forms an automatic polishing system which keeps the polishing tool vertically on the surface of die and maintains constant pneumatic pressure. A synchronization between machining center and polishing robot is accomplished by using M code of machining center. A rulled surface and shadow mask are polished by the developed polishing robot.

• Transactions of Materials Processing
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• v.13 no.8
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• pp.663-670
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• 2004

The bending phenomenon has been known to be occurred by the difference of velocity at the die exit. The difference of velocity at the die exit section can be obtained by the different velocity of billets through the multi-hole container. The difference of velocity at the die exit can be controlled by the two variables, the one of them is the different velocity of extrusion punch through the multi-hole container, the other is the difference of hole diameter of muliti-hole container. In this paper the difference of hole diameter is applied. So it can bend during extruding products because of the different amount of two billets when billets would be bonded in the porthole dies cavity. And the bending curvature can be controlled by the size of holes. The experiments with aluminum material for the curved tube product had been done for circular or rectangular curved tube section. The results of the experiments show that the curved tube product can be formed by the extru-bending process without the defects such as distortion of section and thickness change of wall of tube and folding and wrinkling. The curvature of product can be controlled by shape of cross section and the difference of billet diameters. And it is known that the bonding and extruding and bending process can be done simultaneously in the die cavity by the experiments that rectangular hollow curved tubes could be extruded by porthole dies with four different size billets made of aluminum material. And it shows that bending phenomenon can happen during extruding with for different billets from the analysis by DEFORM-3D.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.118-121
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• 2008

Flexible die is more efficacious than fixed die which is generally used in stretch forming process in view of production cost. Accordingly, in order to verily the validity of the flexible forming process, curved thin skin structure forming analyses using the fixed and flexible die were performed. As results, merit and demerit with regard to the fixed and flexible die were confirmed. The result of the stretch forming process analysis using the flexible die was better than that using the fixed die in view of the elastic recovery. However wrinkles were occurred on the sheet material due to die cavities between the punches in the flexible forming process, thus the solutions against these problems were presented.