• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.104-107
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• 2002

Direct Metal Manufacturing (DMM) is a new additive process that aims to take die making and metalworking in an entirely new direction. It is the blending of five common technologies : lasers, computer-aided design (CAD), computer-aided manufacturing (CAM), sensors and powder metallurgy. The resulting process creates parts by focusing an industrial laser beam onto a tool-steel work piece or platform to create a molten pool of metal. A small stream of powdered tool-steel metal is then injected into the melt pool to increase the size of the molten pool. By moving the laser beam back and forth, under CNC control, and tracing out a pattern determined by a computerized CAD design, the solid metal part is built line-by-line, one layer at a time. DMM produces improved material properties in less time and at a lower cast than is possible with traditional fabrication.

• Tribology and Lubricants
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• v.9 no.1
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• pp.38-44
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• 1993

The present study was undertaken to investigate the dry wear characteristics of die steel STD 11 for cold molding. The wear test was experimentally carried out under different conditions using a wear device, which was made in laboratory, and in which annular surfaces of wear testing specimens wear rubbed in dry sliding condition with varying the sliding speed, contact pressure, and sliding distance. The wear loss by variation of sliding speed was much in 0.3 m/sec and less in higher speed range above its sliding speed according to formation of the boundary lubrication film. The critical sliding speed with maximum value of the specific wear rate switched over to lower speed side according. as contact pressure increased. The critical sliding distance was increased with decrease in oxidation reaction velocity. The depth below subsurface showing maximum hardness (Hv) came out at the position, $60 \mu m$, of the maximum shear stress due to strain hardening.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.26-30
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• 1996

This paper presents the performance of CBN tools in the machining of hardened die-materials, SKD11 and SKD61 steel with HRC 50, by high-speed face milling. Generally, grinding or EDM is being used in machining of hardened materials but the cost is very high. If those can be replaced by cutting, it will be a greatly economical advantage. CBN tool has been recognized as an effective tool in turning, but it has not been in milling. So wear and surface roughness mode of CBN tool for hardened SKD11 and SKD61 steel were investigated by high-speed face milling in this study Also the relation between cutting force and wear mode of CBN tools was investigated.

• Transactions of Materials Processing
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• v.32 no.2
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• pp.61-66
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• 2023

The quality of the sheared surface affects the stretch flangeability of steel sheet. The quality of sheared surface is influenced by several process factors such as die clearance, shape of cutting edge, use of counter punch, and shear. In this paper, the influence of these shearing process factors on the stretch flangeability of the HSS (DP980) was analyzed through a shearing and a stretch flangeability test. When the die clearance was 10%, the effect of these shearing process factors on the stretch flangeability was the greatest, and the use of an acute angle blade was found to be more advantageous in the stretch flangeability than a right angle blade. It was found that the stretch flangeability was improved when active bending was applied during shearing.

• Transactions of Materials Processing
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• v.33 no.1
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• pp.43-49
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• 2024

A high strength steel sheet (HSSS) has widely used to improve the specific rigidity of parts and the safety of the passenger in automotive industries. However, the HSSS is difficult to manufacture precise parts through a forming process due to the reduced elongation and the increased elastic recovery. The goal of the paper is to investigate the improved design of bending dies for DP590 HSSS. The over forming type bending dies with cam systems added to the side of the formed part is proposed to improve the quality of the part. The effects of the die design and the forming parameter on formability and elastic recovery characteristics is examined using finite element analyses (FEAs). From the results of FEAs, proper die design and forming parameters are predicted.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.5
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• pp.515-520
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• 2004

We report on the development of a Piezoelectric valvc that is designed to have a high reliability for fluid control systems, such as mass flow control, transportation and chemical analysis. The valve was fabricated using a MCA(multilayer ceramic actuator), which has a low consumption power, high resolution and accurate control. The fabricated valve is composed of MCA, a valve actuator die and an seat die. The design of the actuator dic was done by FEM(finite element method) modeling, respectively. And, the valve seat die with 6 trenches was made. and the actuator die, which possible to optimize control to MCA, was fabricated. After Si-wafer direct bonding between the seat die and the actuator die, MCA was also anodic bonded to the scat/actuator die structure. PDMS(poly dimethylsiloxane) sealing pad was fabricated to minimize a leak-rate. It was also bonded to scat die and stainless steel package. The flow rate was 9.13 sccm at a supplied voltage of 100 V with a 50 % duty ratio and non-linearity was 2.24 % FS. From these results, the fabricated MCA valve is suitable for a variety of flow control equipments, a medical bio-system, semiconductor fabrication process, automobile and air transportation industry with low cost, batch recess and mass production.

• Design & Manufacturing
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• v.8 no.1
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• pp.35-39
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• 2014

Window roller housings are durable because high-quality source materials such as stainless steel is used in making them. After a series of precise structure analysis, their design is optimized. They are subject to repetitive driving tests of more 100,000 times, durability tests, impact resistance tests, corrosion tests and others. For a long time, gaps often occur in press molded products owing to serious squareness deformation and flatness deformation of them. Severe burrs in press molded products require frequent grinding, which leads to short life cycle and rough or unreliable movement of assembled roller housing, which, in turn, causes product defects. This study focuses on developing measures to resolve existing defects and to improve lifespan of dies by designing and making a window roller shearing die.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.6
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• pp.136-141
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• 2015

Laser surface polishing is a polishing method for improving surface roughness using an integrated laser beam. Using a laser for surface polishing can improve the surface condition without physical contact or chemical action. Laser polishing has mainly been used to polish the surface of diamond or optical articles, such as lenses and glasses. Recently, diverse studies on laser polishing for metals have been conducted. The analytic study of laser surface polishing has been conducted with experimental trials for comparison, so that the proper conditions for laser polishing can be recommended. In this study, laser surface polishing was simulated in order to predict the heat-affected zone on the die steel depending on the power of the pulsed laser. The simulated results were verified by comparing them to those of the experimental trials. Through this study, therefore, the application of FEM to the selection of appropriate laser conditions could be possible.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.2 no.2
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• pp.98-105
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• 2003

In the experimental study, wire EDM was conducted for cold die steel by changing the Wire electrode, peak discharge current and number of finish cut. From the micro structure analysis of SEM photographs, the size of irregular welded and added component on the EDMed surface is decreasing and size of EDMed plane surface is increasing as the decreasing peak current and increasing number of finish cut. From the analysis of coating effect, Zn component is highly contained in Br and Zn Wire EDMed surface and copper component is highly contained in Br and Al wire EDMed surface. Hardness values are Increasing as the increasing peak current and decreasing the number of finish cut The value of hardness is decreasing as Cu, Al, Zn and Br wire electrode because of the residual austenite effect of solid solution copper on solidification, and finally EDMed surface has the highest hardness values for every wire electrode. Yield strength values becomes larger and bending strength values become smaller due to the increasing the hardness. These results are increased as increasing brittleness with hardness.

• Korean Journal of Metals and Materials
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• v.50 no.2
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• pp.176-182
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• 2012

The main purpose of this study was to evaluate the endurance against Al alloy melts and wear resistance of an in-situ synthesized titanium matrix composite (TMC) sleeve for aluminum alloy die-casting. The conventional die-casting shot sleeve material was STD61 tool steel. TMCs have great thermal stability, wear and oxidation resistance. The in-situ reaction between Ti and $B_4C$ leads to two kinds of thermodynamically stable reinforcements, such as TiBw and TiCp. To evaluate the feasibility of the application to a TMCs diecasting shot sleeve, the interfacial reaction behavior was examined between Al alloys melts with TMCs and STD61 tool steel. The pin-on-disk type dry sliding wear test was also investigated for TMCs and STD61 tool steel.