• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.812-815
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• 2000

Injection molding process was taken to manufacture DC motor case that surrounds DC motor used as automobile parts. Up to now, DC motor case has been made by the deep drawing process or bending process of metal materials. Simulations of filling, packing and cooling processes were done by CAE tool like Moldflow software. Optimal delivery system was decided from the analysis of flow balance, and packing and cooling analyses were performed by using the design of experiment to minimize the volumetric shrinkage of molded part and the temperature difference between mold and part.

• Journal of Powder Materials
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• v.23 no.1
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• pp.26-32
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• 2016

Powder injection molding (PIM), which combines the advantages of powder metallurgy and plastic injection molding technologies, has become one of the most efficient methods for the net-shape production of both metal and ceramic components. In this work, plasma display panel glass bodies are prepared by the PIM process. After sintering, the hot isostatic pressing (HIP) process is adopted for improving the density and mechanical properties of the PIMed glass bodies. The mechanical and thermal behaviors of the prepared specimens are analyzed through bending tests and dilatometric analysis, respectively. After HIPing, the flexural strength of the prepared glass body reaches up to 92.17 MPa, which is 1.273 and 2.178 times that of the fused glass body and PIMed bodies, respectively. Moreover, a thermal expansion coefficient of $7.816{\times}10^{-6}/^{\circ}C$ is obtained, which coincides with that of the raw glass powder ($7.5-8.0{\times}10^{-6}/^{\circ}C$), indicating that the glass body is fully densified after the HIP process.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.4
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• pp.8-13
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• 2015

In this study, we fabricated and characterized a nanostructured surface based on a plastic injection molding with a local mold heating (LMH) system. A metal mold core with a closed packed nano convex array (CVA) was achieved by integrated engineering procedures: (1) master template fabrication by anodic aluminum oxidation (AAO), (2) nickel electroforming (NE) process, and (3) post-processing by precision machining. The nickel mold core was utilized to replicate a surface with a closed packed nano concave-array (CCA) based on injection molding using cyclic olefin copolymer (COC) as a plastic material. In particular, an LMH system was introduced to enhance transcription quality of the nano structures by delaying solidification of molten polymer near the surface of the mold core.

• Design & Manufacturing
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• v.15 no.4
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• pp.8-13
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• 2021

A plastic roller for opening and closing the safety door of the injection molding machine was molded. The dimensional change of the measurement position of the roller was studied when the cooling time was applied differently among the molding conditions, and when the temperature of the coolant applied for mold cooling was also applied differently. Cooling times of 300 seconds and 400 seconds, hot and low-temperature coolant were applied. When the low-temperature coolant was applied, the measuring point of the roller shrank by 0.03 mm. However, when the high-temperature coolant was applied, the measuring point shrank by 0.3 mm. It was found that the application of low-temperature coolant among coolants was more suitable for the reference dimension of the molded article compared to the application of high-temperature coolant. Among the cooling water applied for the molding of plastic rollers, when high-temperature coolant is applied, the shrinkage rate measured immediately after ejection was smaller than when low-temperature coolant is applied. However, it was found that post shrinkage, which occurs over time, occurs much larger when high-temperature coolant is applied.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.6
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• pp.63-68
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• 2017

The purpose of this study is to improve the whitening phenomenon around the PET preform gate for blow molding. CAE analysis of plastic injection molding has been applied to design of preform shape and select the injection molding conditions. A ceramic insulation gate with lower thermal conductivity than metal is applied to improve the whitening phenomenon created around the gate in the injection molding process. According to the results of CAE analysis, the warpage deformation at the square corner was estimated to be about 0.34 mm at the bottom. From the results of the temperature history analysis, it was confirmed that the resin near the gate cooled more rapidly than the cavity. Ceramic insulated gates were fabricated to reduce the cooling rate and experiments were conducted to confirm the effectiveness of the whitening phenomenon improvement. As a result of the ceramic insulation gate experiment, it was confirmed that the whitening phenomenon was significantly reduced around the gate.

• The korean journal of orthodontics
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• v.50 no.6
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• pp.401-406
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• 2020

Objective: To investigate and compare the slot sizes and parallelism of metal injection molding (MIM) and computerized numerical control (CNC) brackets. Methods: The following four MIM bracket series with 0.022-inch (in) slots were selected for investigation: Di MIM mini Twin (Ortho Organizers), Mini Diamond Roth (Ormco), Gemini MBT (3M Unitek), and Formula R Roth (Tomy). The following four CNC bracket series with 0.022-in slots were selected for investigation: Econoline MBT (Adenta), Legend mini MBT (GC Orthodontics), Crown mini MBT (Adenta), and Evolve MBT (DB Orthodontics). The slot dimensions were measured using an optical microscope (XTCam-D310M; Mitutoyo) with a resolution of 1 ㎛. The results were statistically analyzed using one-way analysis of variance and the Tukey post-hoc test with a significance level of 0.05. Results: The results indicated that all the investigated slot sizes were oversized with respect to the manufacturers' specifications (0.022 in). Among the eight bracket series, the Di MIM bracket (MIM) was the most oversized by 10.4%, whereas the Evolve bracket (CNC) was the least oversized by 2.6%. The slots in seven of the bracket series had divergent walls instead of parallel ones. The Evolve bracket alone had parallel slot walls. Conclusions: Regardless of the manufacturing method, all the slot sizes of the brackets investigated in this study were significantly oversized; most of the slot walls were nonparallel, except for those of the Evolve bracket. This study could not establish that the CNC method was more accurate than the MIM method in manufacturing bracket slots.

• Design & Manufacturing
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• v.6 no.2
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• pp.64-69
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• 2012

This study looks at plastic mold design for robots and mold manufacture, which is an injection mold branch at The Korea-China-Japan University Grand Prize Contest. Product analysis and layout, molding analysis, and upper and lower core design are carried out to design molds in 2D and 3D. After the design of the cores, NC machining software is used for simulation before actual manufacture. Before the production of end-product, test injection is done to troubleshoot problems like bad dimensions, burr, cracks and stepped pulley.

• Journal of Powder Materials
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• v.21 no.1
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• pp.1-6
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• 2014

Medical technologies are gaining in importance because of scientific and technical progress in medicine and the increasing average lifetime of people. This has opened up a huge market for medical devices, where complex-shaped metallic parts made from biocompatible materials are in great demand. Today many of these components are already being manufactured by powder metallurgy technologies. This includes mass production of standard products and also customized components. In this paper some aspects related to metal injection molding of Ti and its alloys as well as modifications of microstructure and surface finish were discussed. The process chain of additive manufacturing (AM) was described and the current state of the art of AM processes like Selective Laser Melting and electron beam melting for medical applications was presented.

• Journal of Powder Materials
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• v.20 no.5
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• pp.323-331
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• 2013

In this paper, two kinds of advanced powder processing techniques Metal Injection Molding (MIM) and Direct Laser Forming (DLF) are introduced to fabricate complex shaped Ti alloy parts which are widely used for medical and aerospace applications. The MIM process is used to strengthen Ti-6Al-4V alloy compacts by addition of fine Mo, Fe or Cr powders. Enhanced tensile strength of 1030 MPa with 15.1% elongation was obtained by an addition of 4 mass%Cr because of the microstructural modification and also the solution strengthening in beta phase. However, their fatigue strength was lower compared to wrought materials, but was improved by HIP. Subsequently, the effect of feeding layer height (FLH) on the characteristics of the DLF compacts was investigated. In the case of 100 ${\mu}m$ FLH, surface roughness was improved and nearly full density (99.8%) was obtained. Also, tensile strength of 1080 MPa was obtained, which is higher than the ASTM value.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.12-13
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• 2006

The spherical and high quality Titanium fine powder "Tilop" has been produced with gas atomization furnace, Sumitomo Titanium Corporation originally designed. Recently, a new process which can produce Ti-alloy(Ti-6Al-4V) powders by utilizing our gas atomization process, of which raw material is sponge titanium pre-mixed with alloy chips or granules has been also developed. The particle size of gas atomized Ti-alloy powder and the mechanical properties of sintered Ti-alloy compacts prepared by metal injection molding were discussed in this study.