• 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.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.218-223
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• 2000

Ultra precision progressive die have used for above one million's lot size of production part. In the field of design and making tool for press working, the progressive die for sheet metal (STS 304, thickness : 0.5mm) is a specific division. In order to prevent the defects, the optimum design of the production part, strip layout, die design, die making and tryout etc. are necessary. They require analysis of many kinds of important factors, i.e. theory and practice of metal press working and its phenomena, die structure, machining condition for die making, die materials, heat treatment of die component, know-how and so on. In this study, we designed and constructed a progressive die of multi-stage and performed try out. Out of these processes the die development could be taken for advance. Especially the result of tryout and its analysis become the characteristics of this paper (part 1 and part 2) that nothing might be ever seen before such as this type of research method on all the processes. In the part 2 of this study we treated die making and tryout mostly.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.10a
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• pp.375-381
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• 2004

Recently, the evolution in production techniques (e.g. high-speed milling) and the complex shapes involved in modem production design has been increasingly popular. The key to the achievement is a drastic improvement of the dynamic behavior of the machine tool axes used in production machinery. The more complex these tool paths the higher the speed and acceleration requirements. But it is very difficult to reach the target for high speed machine tool because of the limitations of servo system and motion control system. However the direct drive design of machine tool axes, which is based on linear motors and which recently appeared on the market, is a viable candidate to meet the ever increasing demands, because of these advantages such as no backlash, less friction, more mechanical simplicity and very higher acceleration and velocity comparing to the traditional system. This paper focused on the performance tests of the high speed horizontal machine tool based on linear motor. Especially, dynamic characteristics were investigated through circular test and circular form machining test is carried out considering many important parameter. Therefore these several experiments is used to be evaluated the model for prediction of circular motion error and circular machined error.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.213-217
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• 2000

The progressive die are multiple operations performed by means of a die having above two stages, on the each of stages performs a different operation as the sheet metal passes through the die hole. In the field of design and making tool for press working, the progressive die for sheet metal (STS 304, thickness : 0.5mm) is a specific division. in order to prevent the defects, the optimum design of the production part, strip layout, die design, die making and tryout etc. are necessary. They require analysis of many kinds of important factors, i.e. theory and practice of metal press working and its phenomena, die structure, machining condition for die making, die materials, heat treatment of die components, know-how and so on. In this study, we designed and constructed a progressive die of multi-stage and performed try out. Out of these processes the die development could be taken for advance. Especially the result of tryout and its analysis become the characteristics of this paper (part 1 and part 2) that nothing might be ever seen before such as this type of research method on all the processes. In the part 1 of this study we treated die design mostly.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.2
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• pp.105-111
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• 2012

High speed machining is the core technology that influences the performance of machine tools, and the high speed motor spindle is widely used for the high speed machine tools. The important problem in high speed spindle is to minimize the thermal effect by motor and bearing and frequency effect. This paper presents the thermal characteristic analysis and frequency experiment for a high speed spindle considering the flow rate of cooling oil. A high speed spindle is composed of angular contact ceramic ball bearings, high speed built-in motor, oil cooling jacket and so on. The thermal analyses of high speed spindle need to minimize the thermal effect and maximize the cooling effect and they are carried out under the various cooling conditions. Heat generations of the bearing and the high speed motor are estimated from the theoretical and experimental data. To find out the characteristic of vibration, the high speed spindle is excited in operational range. This result can be applied to the design and manufacture of a high speed tapping spindle.

• Journal of the Korean institute of surface engineering
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• v.45 no.1
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• pp.37-42
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• 2012

$WS_2$ powder was added to the Cu/Sn bond metal of diamond micro-blades for machining of semi-conductor and IC chips to improve cutting efficiency. The effect of $WS_2$ additive on cutting efficiency was investigated and compared with the micro-blades with $MoS_2$ developed in previous research. Flexural strength, frictional coefficient, and wear resistance of blades decreased with $WS_2$ but wear depth increased. It was found that the blades including $WS_2$ consumed less momentary energy than the blades containing $MoS_2$ during dicing test. Micro-blades containing $WS_2$ exhibited lower flexural strength than the blades with $MoS_2$ resulting from higher amount of sintering defects relevant to the less effectiveness of $WS_2$ on fluidity. The effect of $WS_2$ and $MoS_2$ on fluidity during sintering was analyzed in terms of mismatching degree between the longitudinal direction of lubricant particles and the perpendicular direction to the compact loading. The blade with 8.1 vol.% of $WS_2$ showed the best cutting efficiency.

• The KSFM Journal of Fluid Machinery
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• v.14 no.6
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• pp.91-95
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• 2011

This paper deals with the detail rotordynamic analysis for the assembly rotor composed of turbine wheel, turbine shaft, connecting arbor, and flange & spindle in order to perform the spin test of turbocharger turbine. Prior to rotordynamic analysis, the 1st spin test was performed but the test was failed by excess vibration in the neighborhood rated speed. It is the reason for this fail that the separation margin between the rated speed and critical speed is not enough, confirmed by rotordynamic analysis results. Since then, the dimension of turbine shaft was modified and the critical speeds were again reviewed for modified assmebly rotor. In results, the separation margin between the rated speed and critical speed is over 20% and then the 2nd spin test was performed successfully. In preparing spin test for turbine, compressor wheels and etc., the geometry design of connecting arbor and dimension of rough machining should be reviewed by considering rotordynamic results, and the separation margin should be enough for successful spin test.

• Design & Manufacturing
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• v.12 no.2
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• pp.46-50
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• 2018

Recently, as machine components and products are getting smaller, it is demanded to develop superprecision production technologies multilaterally. Along with the advancement of production technology, people are paying keener attention to the development of eco-friendly technology and efficient processing technology. Particularly, in many industries related to automobiles, shipbuilding, or airplane components, it is demanded to obtain technology to process multiple micro-holes. On account of this trend, micro-hole processing employing high-power electron beams is rising nowadays, and more interest is being shown in it, too. In Korea, however, the process of manufacturing vaporized amplification sheets influencing high-power electron beam processing technology and the processability considerably has not been developed sufficiently yet. Therefore, this study has applied vaporized amplification sheets manufactured to analyze the processability of high-power electron beams and examine necessity for vaporized amplification sheets.

• Transactions of Materials Processing
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• v.16 no.8
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• pp.575-581
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• 2007

The high dimensional accuracy of the cold forged part could be acquired by the accurate dimensional modification for the die, which is, the dimensional changes from the die through forged part to final part after heat treatment were considered. The experimental and FEM analysis are performed to investigate the dimensional changes from the die to final part on cold forged part, comparing with the machined gear. The dimension of forged part is compared with the die dimension at each stage, such as, machined die, cold forged part, and heat-treated-part. The elastic characteristics and thermal influences on forging stage are analyzed numerically by the $DEFORM-3D^{TM}$. The analyzed residual stress of forged part is considered into the FE-analysis for heat treatment using the $DEFORM-HT^{TM}$. The effects of residual stress affected into the dimensional changes could be investigated by the FEA. Each residual stress of gears was measured practically by laser beam type measurement.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.217-218
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• 2006

This paper presents an investigation on the characteristics for new micro tool dynamometer by using the ultrahigh-speed air turbine spindle. Recently, the ultrahigh-speed micro flat endmilling has been investigated actively due to request of accuracy improvement and productivity of die and mould manufacturing. To perform efficient ultrahigh-speed micro flat endmilling, evaluation of ultrahigh-speed machinability must be studied preferentially and it can be identified by investigation of cutting force. The cutting forces in ultrahigh-speed micro flat endmilling can be measured by micro tool dynamometer. But general dynamometer has low natural frequency and so is improper for measuring very high frequency cutting forces in ultrahigh-speed micro flat endmilling. In this study, the micro tool dynamometer which has very high natural frequency is newly designed.