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안동규,박승화,김형수 한국정밀공학회 2010 International Journal of Precision Engineering and Vol. No.
The aims of the present study is to manufacture an injection mould with a pair of conformal cooling channels in each blade of the mould for a plastic fan part via laser-aided direct metal tooling (DMT) process to achieve both rapid and uniform cooling characteristics. The features of the design and the manufacturing process for the injection mould as well as the characteristics of the manufactured mould were discussed. Three-dimensional injection moulding analyses were performed to obtain a proper design of the conformal cooling channels. Injection moulding experiments were carried out to investigate the practical applicability of the fabricated mould and the influence of the cooling time on the qualities of the moulded product. The results of the experiments showed that a plastic fan part with superior qualities can be fabricated from the designed mould when the cooling time is 13 s. The efficiency of the designed mould was examined through a comparison of the product from the newly designed mould and that from a previously designed mould with linear cooling channels in terms of product qualities as well as the cooling and cycle times. The results of the comparison showed that the newly designed mould can remarkably reduce the positional error distributions and the eccentricity of the moulded product. In addition, it was shown that the cooling and cycle times of the designed mould can be shortened to 35.0 % and 25.7 % of those of the previously designed mould, respectively.
안동규,김대원,Yeol-Ui Yoon 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.1
The objective of this paper is to examine the influence of injection molding parameters on the core shift to obtain the optimal injection molding conditions of a plastic battery case with thin and deep walls using numerical analyses and experiments. Unlike conventional injection molding analysis, the flexible parts of the mold were represented by 3-D tetrahedron meshes to consider the core shift in the numerical analysis. The design of experiments (DOE) was used to estimate the proper molding conditions that minimize the core shift and a dominant parameter. The results of the DOE showed that the dominant parameter is the injection pressure, and the core shift decreases when the injection pressure decreases. In addition, it was shown that the initial mold temperature and the injection time hardly affect the core shift. The results of the experiments showed that products without warpage are manufactured when the injection pressure is nearly 32 MPa. Comparing the results of the analyses with those of the experiments, optimal injection molding conditions were determined. In addition, it was shown that the core shift should be considered to simulate the injection molding process of a plastic battery case with thin and deep walls.
안동규,이상용 대한설비관리학회 1997 대한설비관리학회지 Vol.2 No.2
Assuming that confidence in making jugements on these individual ratios can be different, a study of the properties of different eigen weight vectors, including that of Saaty and the one recently proposed by Cogger and Yu is performed. A general framework for construction of eigen weight vectors incorporating this differing that confidence in obtaining the individual ratios will be proposed and discussed. The algorithm used in this study is based on the concepts of vague set theory. Linguistic variables and vague values are used to facilitate a decision maker's subjective assessment about attribute weightings and the appropriateness of alternative versus selection attributes in order to obtain final scores which are called vague appropriateness indices. A numerical example is presented to show the practical applicability.
VLM-s 공정을 위한 EPS 폼의 단순 경사 열선 절단시 절단 경사각이 절단폭과 모서리 형상에 미치는 영향
안동규,양동열 대한용접접합학회 2003 대한용접·접합학회지 Vol.21 No.5
The dimensional accuracy and global roughness between successive layers of VLM-s, which is a new rapid prototyping process using hotwire cutter and EPS foam, depend significantly on the operating parameters of hotwire cutter. In the present study, the effect of cutting angle on the kerf width and edge shape in hotwire cutting of EPS foam for the case of single-sloped cutting with one cutting angle was investigated. Through single-sloped cutting tests, the modified relationship between kerf width and effective heat input, considering the effect of the cutting angle, and the relationship between the melted area and the cutting angle were obtained. In order to investigate the effect of cutting angles on the thermal field in EPS foam, transient heat transfer analyses using single-sloped volumetric heat flux model and locally-conformed mesh were performed. Through the comparison between experimental and numerical results, it was shown that the proposed analysis model is needed to estimate the three-dimensional temperature distribution of the EPS foam for the case of single-sloped hotwire cutting.
고출력 CW Nd:YAG 레이저를 이용한 인코넬 718 판재 절단시 모서리부 절단 특성 분석
안동규,변경원,Ahn, Dong-Gyu,Byun, Kyung-Won 대한용접접합학회 2008 대한용접·접합학회지 Vol.26 No.5
The objective of this paper is to investigate the effects of the laser power, the material thickness, comer angles, and the loop size on the formation of the comer in the cutting of Inconel 718 super-alloy sheet using high-power CW Nd: YAG laser. In order to investigate the influence of comer angles and loop sizes on the melted area and the formation of comer in the sharp comer, angular cutting tests and loop cutting tests were carried out. The results of the angular cutting tests were shown that the melted area is minimized and the melting mode is changed from nose melting in the thickness direction to the secondary melting induced by the attached dross when the comer angle is $90^{\circ}$. Through the results of loop cutting tests, the variation of the melted area and the comer shape in the sharp comer according to the loop size were examined. In addition, it was shown that a proper loop size is approximately 3 mm. The results of above experiments will be reflected on the knowledge base to generate optimal cutting path of the laser.