• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.846-849
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• 2000

In this paper backward extrusion process with lower die rotation was studied to improve the conventional backward extrusion problems ; requirement of large forming machine, the difficulty to selecting of die material caused by high surface pressure, high cost of forming machine caused by improvement of noise and vibration, and etc. In this experiment, model material, plasticine, was used of specimen. The result values of torsional and conventional backward extrusions were analyzed and compared. FE-simulation is used for analysis with DEFPRM-3D. These results show that the torsional backward extrusion is very useful process because this process can obtain the homogeneous deformation, low forming load. Decreasing forming load improves die life and makes it possible to use press of relatively low capacity. Also this process can reduce corner cavity, improve the initial cast-structure, owing to the high deformation and uniform starin distribution.

• 소성∙가공
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• 제8권2호
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• pp.188-199
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• 1999

Semi-Solid Forming Process(Thixoforming, Rheocasting) is a novel forming process which has some advantages compared with conventional die casting, squeeze casting and hot/cold forging. In this study. Thixoforming process was selected as analysis processing in terms of billet handling and easiness of automation process. The Thixoforming process consists of reheating process of billet, billet handling, filling inot the die cavity and solidification of SSM part. In filling process, two rheology models which were Newtonian and Non-Nettonian model (Ostwald-deWaele)were verified with experimental results. The Ostwald-deWaele model shows the good agreement to the real flow and filling phenomena in die cavity. To give a boost the economical efficiency of Thixoforming process and to ensure the good forming result, reheating device coupled die set was proposed and the initial billet temperature for system that was found from experimental resluts. This study presents an overview of application of numerical analysis for simulation of semi-solid metal forming process to reduce the lead time for development of manufacturing part in industrial field.

• Design & Manufacturing
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• 제9권1호
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• pp.23-26
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• 2015

For mass production of plastics, injection molds have multi-cavities. However, filling imbalance between cavity to cavity always has occurred in multi-cavities mold, and this has caused low quality of plastics part. In this study, the closed-loop-control system which can control temperature of hot manifold and nozzle in hot runner mold for filling balance has been suggested, and a series of experiment about difference of filling time and weight in cavity-to-cavity was conducted. As a result of using closed-loop-control system, a remarkable improvement in reducing filling imbalance was confirmed.

• Design & Manufacturing
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• 제9권3호
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• pp.34-40
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• 2015

In the study, Three-dimensional drawing parts for conformal cooling circuit cavity & core and their 3D Metal parts using DMLS(Direct MetalLaser Sintering) and NC integrated machining center were showned. For conformal cooling circuit cavity and core parts, I discussed its practicality to DMLS multiple machinins process introducing general manufacturing process and comparing with them.

• 대한기계학회논문집
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• 제17권6호
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• pp.1478-1485
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• 1993

본 연구에서는 압축 성형다이 가열선의 최적위치를 결정하는 문제를 다이의 형상 최적설계 문제로 정식화하고자 한다. 최적화 문제의 목적은 다이 내면의 온도를 지정된 온도로 균일하게 유지하는 것이다. 또한 Lee, Choi와 Kwak의 형상 설계 민감 도 해석을 위한 직접 미분 방법을 응용하여 가열선 위치변화에 관한 민감도 계산을 위한 경계 적분 방정식을 유도하고, 경계요소법으로 온도와 온도의 민감도를 해석하고 자 한다. 수치적 응용의 예로서, 넓은 평판의 성형을 위한 압축 성형다이의 가열선의 최적위치를 결정하는 문제를 다루고, 최적위치에서 가열선의 개수가 온도의 균일성에 미치는 영향을 검토한다.

• 소성∙가공
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• 제9권5호
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• pp.533-538
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• 2000

This study has been carried out to develop a CRT die using hot forging. The conventional CRT die made by casting has defects such as void and inclusion. These defects of the cast die make micro-spots on the surface of the CRT which affect the quality of the final product. So, a hot forging process is developed to avoid these defects of CRT die by the model material test and the rigid-plastic FEM. Firstly, model material tests are carried out with plasticine billets in order to investigate the material flow pattern in the die cavity and to get the reasonable initial values for designing the preform in the FE simulation. And then a finite element analysis has been performed to Predict the preform and the forging load of a CRT die. We also suggest an integrated die-set which combines two die-sets into one die-set to save manufacturing time and cost in case of similar die-size.

• 한국기계가공학회지
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• 제5권2호
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• pp.27-35
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• 2006

Al used in automobiles is mostly material, and according to the innovation of technique is in rapid development. Al die casting is an important field as today's trend of lightweight on automobiles. Valve housing in steering system improves driver's controling. The valve housing which is widely reliable to the most automobiles are developed this moment in our automobile industry. Therefore, they are produced by casting method which cost three times or even more expensive in production. If valve housing which is a part of steering system is produced by gravity casting, the space for manufacturing equipment will be increased, and more time and workers would be brought into service. For such reason, die casting would replace gravity casting in order to minimize cost of time, manpower, and working space. This study is the forming analysis of the 2 cavity die casting for automobile valve housing.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 The 8th Asian Symposium on Precision Forging ASPF
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• pp.152-157
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• 2003

A typical die-set for enclosed-die forging of half axle gears in double action hydraulic press is presented, the important factors those influence on precision forming of half axle gears are analyzed, warm forming process of half axle gears is simulated by FEM software $DEFORM\_3D$. The results show, that proper die structure and dimension, suitable web thickness and position can improve material filling, ensure full filling of tooth cavity.

• 한국정밀공학회지
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• 제18권7호
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• pp.167-173
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• 2001

The simulated die-casting process in which the traditional plaster casting process is combined with Rapid Prototyping technology is being used to produce AI, Mg, and Zn die-casting prototypes. Unlike in the die-casting process, molten metal in the conventional plaster casting process is fed via a gravity pour into a mold and the mold does not cool as quickly as a die-casting mold. The plaster castings have much larger and grosser grain structure as compared with the normal die-castings and the thin walls of the plaster mold cavity may not be completely filled. Because of lower mechanical properties induced by the large grain structure and incomplete filling, the conventional plaster casting process is not suitable for the trial die-casting process to obtain quality prototypes. In this work, an enhanced trial die-casting process has been developed in which molten metal in the plaster mold cavity is vibrated and pressurized simultaneously. Patterns for the casting are made by Rapid Prototyping technologies and then plaster molds, which have a runner system, are made using these patterns. Pressurized vibration to imparted molten metal has made grain structure of castings much finer and improved fluidity of the molten enough to obtain complete filling at thin walls which may not be filled in the conventional plaster casting process..

• 한국주조공학회지
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• 제35권4호
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• pp.80-87
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• 2015

The Al die casting process has been widely used in the manufacturing of automotive parts when the process requires near-net shape casting and a high productive rate. However, porosity arises in the casting process, and this hampers the wider use of this method for the creation of high-durability automotive components. The porosity can be controlled by the shot condition, but, it is critical to set the shot condition in the sleeve, and it remains difficult to optimize the shot condition to avoid air entrapment efficiently. In this study, the 4.5 mm, 2.0 mm plate die castings were fabricated under various shot conditions, such as plunger velocities of 0.7 m/s ~ 3.0 m/s and fast shot set points of the cavity of -25%, 0%, 25%, and 50%. The mold filling behavior of Al melts in the cavity was analyzed by a numerical method. Also, according to the shot conditions, the results of numerical analyses were compared to those of die-casting experiments. The porosity levels of the plate castings were analyzed by X-ray CT images and by density and microstructural analyses. The effects of the porosity on the mechanical properties were analyzed by tensile tests and hardness tests. The simulation results are in good general agreements with the die-casting experimental results. When plunger velocity and fast shot set point are 1.0 m/s and cavity 25% position, castings had optimum condition for good mechanical properties and a low level of porosity.