• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.6
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• pp.288-293
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• 2023

To optimize the process parameters of laser powder bed fusion process to fabricate the high density STS316L alloy, the effect of laser power, scanning speed and hatching distance on the relative density was studied. Tensile properties of additively manufactured STS316L alloy using optimized parameters was also evaluated according to the build direction. As a result of additive manufacturing process under the energy density of 55.6 J/mm³, 83.3 J/mm³ and 111.1 J/mm³, high density STS316L specimens was suitably fabricated when the energy density, power and scan speed were 83.3 J/mm³, 225 W and 1000 mm/s, respectively. The yield strength, ultimate tensile strength, and elongation of STS316L specimens in direction perpendicular to the build direction, show the most competitive values. Anisotropic shape of the pores and the lack of fusion defects probably caused strain localization which result in deterioration of tensile properties.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.12
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• pp.185-194
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• 2000

Rapid Prototyping(RP) techniques have their unique characteristics according to the working principles: stair-stepped surface of parts due to layer-by-layer stacking, low build speed caused by line-by-line solidification to build one layer, and additional post processing to improve surface roughness, so it is required very high cost to introduce and to maintain of RP apparatus. The objective of this study is to develop a new RP process, Variable Lamination Manufacturing using linear hotwire cutting technique and expandable polystyrene foam sheet as part material(VLM-S), and to investigate characteristics of part material, cutting characteristics by using linear hotwire cutting system and bonding. Experiments were carried out to investigate mechanical properties of part material such as anisotropy and directional tensile strength. In order to obtain optimal dimensional accuracy, surface roughness, and reduced cutting time, addition experiments were performed to find the relationship between cutting speed and cutting offset of hotwire, and heat generation of hotwire per unit length. So, adhesion strength tests according to ASTM test procedure showed that delamination did not occur at bonded area. Based on the data, a clover-shape was fabricated using unit shape part(USP) it is generated hotwire cutting. The results of present study have been reflected on the enhancement of the VLM-S process and apparatus.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.10
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• pp.865-871
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• 2016

In recent years, traditional scaffold fabrication techniques such as gas foaming, salt leaching, sponge replica, and freeze casting in tissue engineering have significantly limited sufficient mechanical property and cell interaction effect due to only random pores. Fused deposition modeling is the most apposite technology for fabricating the 3D scaffolds using the polymeric materials in tissue engineering application. In this study, 3D slurry mould was fabricated with a blended biphasic calcium phosphate (BCP)/Silica/Alginic acid sodium salt slurry in PCL mould and heated for two hours at $100^{\circ}C$ to harden the blended slurry. 3D dual-pore BCP/Silica scaffold, composed of macro pores interconnected with micro pores, was successfully fabricated by sintering at furnace of $1100^{\circ}C$. Surface morphology and 3D shape of dual-pore BCP/Silica scaffold from scanning electron microscopy were observed. Also, the mechanical properties of 3D BCP/Silica scaffold, according to blending ratio of alginic acid sodium salt, were evaluated through compression test.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.4
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• pp.892-898
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• 2008

3D rapid prototyping is the manufacturing technology to fabricate a prototype with the data stored in a computer, which differs from conventional casting technology in terms of an additive process. Various 3D rapid prototyping techniques such as stereolithograpy. fused deposition modeling. selective laser sintering, laminated object manufacturing have been developed but among them, 3D inkjet printing has a unique feature that materials could be jetted to directly form the body of a prototype, which could be a finished product functionally and structurally. However, this needs ink with a high solid content, which tends to increase the dynamic viscosity of ink. The increase of ink viscositytends to restrict the jettable range of ink and hence the jetting conditions should be optimized. The intrinsic speed of sound in a hot melt ink with ceramic nanoparticles dispersed is one of key components to determine the jettable range of ink. In this paper, the way to measure the intrinsic speed of sound in a hot melt ceramic ink is proposed and its influence on the jetting condition is discussed.

• Journal of the Korea Convergence Society
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• v.11 no.2
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• pp.225-230
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• 2020

Using the 3D printing method in the product manufacturing is a very innovative and useful technology. However, in the field of jewelry, it is a limited technology used only in a field of manufacturing process. To overcome this limitations in the jewelry production process, most popular and easy 3D printing method was selected, and the printing time and condition was limited. In this study, to find out the 3D printing method applicability to jewelry work manufacturing, the prototypes through casting and non-casting methods were completed and compared. As a result, the FDM printing method has a very positive advantage in terms of cost and time, but there is a disadvantage that the layered structure is not erased on the surface and the completeness of the surface forming is poor due to the residue of the filament generated during the printing process. The DLP printing method has the advantage that the surface treatment is even and completion is high, while the cost and time are inefficient. However, both printing methods were found to be suitable for the use of jewelry manufacturing, and if the efficient printing method was selected for the design of the jewelry in the future, better work research could be conducted.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.327-330
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• 2004

Laser aided direct metal deposition (LADMD) process offers the ability to make a metal component directly from 3-D CAD dimensions. A 3-D object can be formed by repeating laser cladding layer by layer. The key of the build-up mechanism is the effective control of powder delivery and laser power to be irradiated into the melt-pool. A feedback control system using optical sensors is introduced to control laser power and powder mass flow rate. Using H13 tool steel and $CO_2$ laser system, comprehensive analysis are executed to test the efficiency of the system. In addition, the dimensional characteristics of directed deposited material are investigated with the parameters of deposition thickness, laser power, traverse speed and powder mass flow rate.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.101-104
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• 1997

The purpose of this study is the development of the extensive Rapid Prototyping Technique, which can resolve the long-term manufacturing process, shrinkage and deformation occurring rapid prototyping technique. To begin with, the various specimens for tensile and bending test were manufactured on the basis of this modeling technology. Then, many kinds of the laminate pieces for the test were made by using the sheet steels 1 mm and 2 mm thickness which is composed of the same ingredient. Not only the mechanical strength of the both of the laminate specimens by the developed Rapid Prototyping using projection welding and non-laminate specimens of 5 mm thickness were evaluated, but the mechanical strength of the specimens of the tensile and bending test composed of heterogeneous components were also estimated.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.883-886
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• 1997

In all Rapid Prototyping (RP) processes, a CAD solid model is sliced ito thin layers of uniform, but not necessarily constant, thickness in the building direction. Each cross-sectional layer is successively deposited and, at the same tim, bonded onto the previous layer; the stacked layers form a physical part of the model. The objective of this study is to develop a methode for calculating the rotational angle(θ/sub x/, θ/sub y/) of the linear hotwire cutting system in the three-dimensional space for the Variable Lamination Manufacturing process using expandable polystyrene foam sheet (VLM-S). In order to examine the applicability of the developed method to VLM-S, various three-dimensional shapes, such s a screw, an extruded cross, and a figure of Sonokong, were made using the data obtaiend from the method.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.4
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• pp.56-62
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• 2006

Various kinds of rapid prototyping processes are available, such as stereo-lithography apparatus(SLA), fused deposition modeling(FDM), selective laser sintering(SLS), 3 dimensional printing(3DP), and laminated object manufacturing(LOM). In this study, benchmark tests are carried out to obtain detailed informations about surface roughness and mechanical properties of those parts. Although the patterns and roughness averages of part surface are dependent on the surface direction, the roughness of SLA part is the best and that of FDM or 3DP part is the worst. It is shown that FDM part has an advantage in impact strength, SLS(or EOS) part in compressive strength, and LOM part has an advantage in tensile strength and heat resistance, but the change of building direction in FDM and LOM processes severely weakens the tensile and impact strengths.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.7
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• pp.85-90
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• 1998

The business of manufacturing is increasingly becoming time-compressing, precise and long-life oriented, owing to various needs from the consumers and harsh global competition. With the emergence of the layer laminate manufacturing method, it is possible to produce prototypes directly from 3D CAD and additive process, the production time and cost have shortened dramatically. However there are some problems like surface-step, dimensional deviation and warp. A newly developed powder casting is suitable for rapid-manufacturing metallic tools. Powder casting can serve as a promising rapid tooling method because of high density characteristics and low dimensional shrinkage below 0.1％ during sintering and infiltration. By this process, we have realized significant time savings bypassing the wait for prototype tooling and cost savings eliminating the expense of conventional prototype tooling process.