• Design & Manufacturing
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• v.2 no.6
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• pp.23-27
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• 2008

It is well known that the family-mold has an advantage to reduce the cost for production and mold. However, defects are frequently occurred by over packing the smaller volume cavity during molding, especially when the family-mold has a volumetric difference between two cavities. In this study, the cavity-filling imbalance was confirmed by the temperature and the pressure sensors, and a variable-runner system was developed for balancing the cavity-filling. Experiments of balancing the cavity filling was carried out in the family-mold with the variable-runner system, and balancing the cavity-filling was confirmed by changing the cross-sectional area of a runner in the variable-runner system with the temperature and pressure sensors. The influence of the injection speed to the balancing-capability of the variable-runner system was also examined in the experiment.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.2
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• pp.340-348
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• 2002

Deformation analysis of injection molded articles whose geometry is considered as the assembly of thin flat plates has been conducted. For the in-mold analysis, thermo-viscoelastic stress calculation of thermo-rheologically simple amorphous polymer and in-mold deformation calculation considering the in-plane mold constraint have been done. Free volume theory has been used to represent the non-equilibrium density state during the fast cooling. At ejection, instantaneous deformation takes place due to the redistribution of in-mold residual stress. During out-of-mold cooling after ejection, thermoelastic model based on the effective temperature has been adopted for the calculation of out-of-mold deformation. In this study, emphasis is also made on the treatment with regard to lateral constraint types during molding process. Two typical mold geometries are used to test the numerical simulation modeling developed in this study.

• Design & Manufacturing
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• v.11 no.1
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• pp.26-29
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• 2017

Burrs generated during shear forming such as notching and piercing may cause lifting during product assembly, which may deteriorate the productivity and quality of products. In this study, various shear angles and variable clearances between the punch and the die were applied in experimental notching tests to investigate the shear fracture surface and the burr height due to various conditions. The experimental results show that the clearance has the greatest effect on shear and fracture surfaces. It is considered that the height of the shear section increases slightly as the shear angle increases.

• Journal of Navigation and Port Research
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• v.32 no.9
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• pp.699-703
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• 2008

Fiber reinforced plastics (FRP) have been widely used because of their high specific strength, high specific stiffness and etc. Although these kinds of FRP have various merits in applications, it has been had one of the complicated problems to manufacture their wooden mold. For these reasons, the simple methods to manufacture the mold required in the FRP industries. To improve these kinds of problems, the molding system using composite materials was developed. By this new manufacturing techniques and high functional FRP composite mold was built. Comparing with wooden mold, the process efficiencies of frame manufacturing process and inner mold manufacturing process were improved approximately 40% and 70%, respectively.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.36 no.3
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• pp.52-59
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• 2004

The greater Increase of the demand for environmental friendly materials especially for packaging industry leads to the larger interest in the reusable and recycable materials such as pulp mold. Although the pulp mold has great characteristics for packaging, some deficiency compared with other packaging material like EPS(Expandable Polystyrene) need to be overcome, for example, the relative higher cost. In this report, since the water drainage rate at the forming zone of a wet pulp mold process could have a great influence on the economical efficiency not only by increasing machine speed but also reducing the drying energy, the optimum ways for increasing drainage were investigated The mechanism of vacuum drainage In pulp mold forming was successfully evaluated by using RDA(Retention and Darinage Analyzer). Since the conditions of stock were greatly affected by the pulping time of low consistency pulper, the optimum pupling time was investigated with considerations of all stock preparation processes. The change of stock temperature and the addition of polyelectrolyte could improve the vacuum drainage rate. It was founded that the wire mesh types of mold former had a little influence on the retention because of the relatively mild vacuum drainage. However, the bigger size of dewatering hole showed better drainage rate and could reduce the plugging and con lamination of mold.

• Transactions of Materials Processing
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• v.23 no.8
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• pp.482-488
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• 2014

Flexible forming technology has advantages in sheet metal forming, because it can be implemented to produce various shaped molds using a single apparatus. Due to this advantage, it is possible to apply it to the manufacture of an aircraft winglet mold. Presently, most aircraft winglets are manufactured from composite materials. Therefore, the mold for the curing process is an essential element in the fabrication of such composite materials. Compared to conventional mold forming, flexible forming has some advantages such as reduced manufacturing cost and uniformity of mold thickness. If the thickness of the mold is consistent, then the heat transfer will occur uniformly during the curing process leading to improved formability of the composite material. In the current study, numerical simulations were performed to investigate the possibility of flexible forming for manufacturing of the winglet mold. In order to match the size of the actual product, the shape of objective surface was divided to fit the dimensions of the apparatus. The results from the numerical simulations are compared with the objective surface to verify the accuracy. In conclusion, the current study confirms the feasibility and the potential to manufacture winglet molds by flexible forming.

• Design & Manufacturing
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• v.1 no.1
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• pp.27-32
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• 2007

In the optical application demand for high quality lens is increasing. Plastics lenses are demanded more than glass lenses for large size lenses as well as micro-size lenses. It is difficult to apply typical straight cooling channels of injection mold to lens molding due to its non-uniform temperature distribution. In this study, we manufactured molds for plastic lenses with the conventional cooling channels and conformal cooling channels produced by the DMLS process. We evaluated cooling performance for the 2 molds by injection molding experiment. Also, uniformity of the temperature distribution was tested by infrared camera and temperature monitoring. We confirmed that the cooling performance and temperature uniformity with the conformal cooling channels is much improved from the ones with the conventional. The cooling time with the conformal cooling channels was reduced 30% compared with the conventional cooling channels.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.4
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• pp.525-540
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• 1997

The effect of mold rotation on the transport process and resultant macrosegregation pattern during solidification of an Al-Cu alloy contained in a vertical axisymmetric annular mold cooled from the inner wall is numerically investigated. The mold initially at rest starts to rotate at a prescribed angular velocity simultaneously with the beginning of cooling. Computed results for a representative case show that the mold rotation essentially suppresses the development of both thermal and solutal convections in the melt, creating distinct characteristics such as the liquidus front, flow pattern and temperature distribution from those for the stationary mold. Thermal convection which develops at the early stages of cooling is soon extinguished by the rotating flow induced during spin-up, and thus does not effectively remove the initial superheat from the melt. On the other hand, solutal convection, though it weakens considerably and is confined within the mushy zone, still predominates over the solute redistribution process. With increasing the angular velocity, the solute transport in the axial direction is enhanced, whereas that in the radial direction is reduced. The final macrosegregation formed in the mold rotating at moderate angular velocities appears to be favorable in comparison with the stationary casting, in that not only relatively homogenized composition is achieved, but also a severely positive-segregated channel is restrained.

• Journal of Korea Foundry Society
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• v.25 no.5
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• pp.209-215
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• 2005

The design of the Metal mold casting should consider several variables such as the material properties and shape of the mold. In particular, the thermal stress generated by the thermal expansion and contraction depending on the thermal gradient of the mold causes partial plastic deformation on the mold, which causes damage or fracture of the cast. Consequently, the thermal deformation along with thermal stress leads to thermal deformation of the cast itself. In this study, the temperature analysis of the cast and mold is simulated by FDM to control the thermal deformation and stress as a result of the thermal gradient of mold. Using the results from FDM simulation, the thermal deformation and stress are analyzed by FEM and, the optimal mold design with minimum thermal deformation of the cast is suggested.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.6
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• pp.1008-1012
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• 2012

Injection molds are fabricated by assembling a number of plates in which mold core and cavity components are inserted. The assembled structure causes a number of contact interfaces between each component where the heat transfer is affected by the thermal contact resistance. However, the mold assembly has been treated as a one body in numerical analyses of injection molding, which has a limitation in predicting the mold temperature distribution during the molding cycle. In this study, a numerical approach that considers the thermal contact effect is proposed to predict the heat transfer characteristics of an injection mold assembly. To find the thermal contact conductance between the mold core and plate, a number of finite element (FE) simulations were performed with the design of experiment (DOE) and statistical analysis. Thus, the heat transfer analyses using the obtained conductance values can provide more reliable results than conventional one-body simulations.