• Journal of the Korean Society for Precision Engineering
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• v.15 no.8
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• pp.39-45
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• 1998

In the previous study. the powder casting was attempted as the rapid tooling. The powder casting was the process to cast dry powder into the casting mold transferred from R/P model and infiltrate the liquid binder to solidify the powder. And then, the melted copper was infiltrated to control the shrinkage rate of the final mold Conseqently, the shrinkage rate was under 0.1% through that process. The mechanical characteristic was also excellent. Generally, in the slurry casting, the alumina powder and the water soluble phenol were mainly used. However, the mechanical property of the phenol was not good enough to apply to molds directly. In this study, aluminium powder filled with epoxy is applicated to the slurry casting to solve these problems. The mechanical and thermal properties are better than phenol because the epoxy is the thermosetting resin. We achieved a successful result that the shrinkage rate is shortened about 0.047%. Futhermore, the manufacturing time and cost savings are significant. Finally, we assume that the developing possibility of this process is very optimistic.

• Transactions of Materials Processing
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• v.16 no.7
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• pp.549-554
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• 2007

The objective of this paper is to investigate into the fabrication technology of cores for the injection mould with three-dimensional conformal cooling channels to reduce the cooling time. The location of the conformal cooling channels has been determined through the injection molding analysis. The mould has been manufactured from a hybrid rapid tooling technology, which is combined a direct metal rapid tooling with a machining process. Several injection molding experiments have been performed to examine the productivity and the validity of the designed mould. From the results of the experiments, it has been shown that the proposed mould can mold a final product within a cooling time of 3 seconds and a cycle time of 21 seconds, respectively.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.1
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• pp.91-98
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• 2003

Removal of gas in a mold has been a big problem in pressing mold or in injection mold. Air vent has been used to solve the problem, but it has weak points such as the increased cost, the increased number of process, and vent marks on the surface of a product. In this study, the sintering method and rapid tooling method are used for making porous metal mold. Porous metal mold has many open pores, which are very small. When porous metal mold is used for pressing mold or injection mold, all process would be made short, produce cost would be down, and vent marks would be not leaved on the surface of a product. Characteristic of porous material varies from sintering conditions, which are the length of sintering time, sintering temperature and sintering atmosphere etc. This study will find optimized sintering condition for the porous metal mold.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.02a
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• pp.187-194
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• 2002

This paper describes the experimental results on direct selective laser sintering of WC-Co mixture for rapid tooling. The experiments were carried out within an air, argon and nitrogen atmosphere. Coupons of single layer were sintered at various laser powers, scanning speeds and scan spacings. As the energy density (energy per unit scanned area) is increased, the thickness of coupons is increased. The main problem took place during sintering within an air atmosphere was severe oxidation of WC-Co mixture. As the laser power is increased and/or scanning speed is decreased, more severe oxidation occurred. Within an argon and nitrogen atmosphere the oxidation is reduced significantly. Experiments on multi-layer sintering were also carried out.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.308-311
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• 2002

Removal of gas in a mold has been a big problem in pressing mold or in injection mold. Air vent has been used to solve the problem, but it has weak points such as the Increased cost, the increased number of process. and vent marks on the surface of a product. In this study, the sintering method and rapid tooling method are used for making porous metal mold. Porous metal mold has many open pores, which are very small. When porous metal mold is used for pressing mold or injection mold, all process would be made short, produce cost would be down, and vent marks would be not leaved on the surface of a product. Characteristic of Porous material varies from sintering conditions, which are the length of sintering time, sintering temperature and sintering atmosphere etc. This study will find optimized sintering condition for the porous metal mold.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.402-407
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• 2002

Laminate tooling process is a fast and simple method to make metal tools directly for various molding processes such as injection molding in rapid prototyping field. Metal sheets are usually cut, stacked, aligned and joined with brazing or soldering. Through the joining process, all of the metal sheet layers should be rigidly joined. When joining process parameters are not appropriate, there would be defects in the layers. Among various types of defects, non-bonded gaps of the tool surface are of great importance, because they directly affect the surface quality and dimensional accuracy of the final products. If a laminate tool with defects has to be abandoned, it could lead to great loss of time and cost. Therefore a repair method for non-bonded gaps of the surface is essential and has important meaning for rapid prototyping. In this study, a rapid laminate tooling system composed of a CO2 laser, a furnace, and a milling machine was developed. Metal sheets were joined by furnace brazing, dip soldering and adhesive bonding. Joined laminate tools were machined by a high-speed milling machine to improve surface quality. Also, repair brazing and soldering methods of the laminates using the $CO_2$ laser system have been investigated. ill laser repair process, the beam duration, beam power and beam profile were of great importance, and their effects were simulated by [mite element methods. The simulation results were compared with the experimental ones, and optimal parameters for laser repair process were investigated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.8
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• pp.1371-1379
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• 2003

RP&M (Rapid Prototyping and Manufacturing) is the most appropriate technology for the small-lot production system, because the production cycle is getting shorter owing to various needs of the consumer. In this paper, rapid tooling technology is applied to the casting process. The casting process has the ability to reflect complicated shapes in one process. But it has not been widely used to make a die and mold because of the poor surface quality caused by air bubbles on the surface of the casting product. In this study, the porous casting mold is fabricated from a mixture of plaster and water-soluble binder. The porous casting mold can improve the characteristics of casting products with the help of the vacuum sealed casting process. The vacuum sealed casting process is an advanced technology that removes the air bubbles between the porous casting mould and the liquid metal, thus making the surface of the casting product finer. The purpose of this paper is to develop a high quality shoe mold using porous casting mold and to apply the RP&M technology to the shoe industry.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.6
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• pp.36-44
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• 1999

The rapid Tooling technique is classified into two methods: one to directly utilize the model which was made by rapid prototyping technologies for dies, and the other to make a transferred type using the model as a master model and create dies and molds using it. In this study, the Al powder filled resin was made several mixed ratios and meshes sizes, and applied to slurry casting. And, variation of mechanical characteristics such as the shrinkage rate, the tensile strength, the elongation, the hardness, and surface roughness, are measured to compare. Consequently, as higher is the powder mixed ration and as smaller is the grain size of the power, the mechanical characteristics of the final mold are improved. Finally, the metal short fiber which can be fabricated easily and cheaply, if the self-excited vibration of an elastic tool, was also applied to slurry casting. It has been found tat the hardness gets higher, while the shrinkage rate lower, if mixed with short fiber.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.12
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• pp.7-13
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• 1999

The potential for growth and the future impact of Rapid Prototyping that it will have on the product development cycle are enormous. Since making tools, precedes making parts, Rapid Tooling becomes widely used in automobile, aerospace, electronic, and other industries. In this study, master models formed by Rapid Prototyping of Stereolithography have been applied for vacuum casting to obtain silicone patterns which have transformed into epoxy models. The epoxy models have been measured to check dimension errors, and tested their functions. These checking and measurement have provided information on plastic injection possibilities and data for die design, Temporary die making with the materials of Aluminum/Epoxy and powder injection metal (PIM) has also been discussed in terms of hardness, surface roughness, and SEM microstructures.

• Transactions of Materials Processing
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• v.10 no.6
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• pp.500-508
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• 2001

The integration of Rapid prototyping (RP) and Rapid Tooling (RT) has the potential for rapid net shaping of thee-dimensional parts, which have a geometrical complexity. In this study, a new R)P process, (VLM-SP), was proposed to manufacture net shapes of three-dimensional prototypes and it was shown that VLM-SP is an effective and economic process through the comparison of building time, building cost and dimensional accuracy for the test parts with the commercial RP processes ; LOM and FDM. In addition, the metal parts, which are a spanner shape and a clover punch, were produced by the plaster casting as one of RT using the prototypes of VLM-SP.