• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.10
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• pp.6258-6263
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• 2014

The LDC (Low Voltage DC-DC Converter) used for hybrid vehicles and electric vehicles was utilized to supply the electric apparatus load with a voltage and to charge the auxiliary batteries by receiving a high DC voltage from the high voltage battery. The LDC has a long-time load test during the manufacturing process. On the other hand, it has the disadvantage of considerable energy consumption because it has the structure to release the power as 100% heat during a load test. Therefore, in this paper, a recycling load test method was proposed and 75~90% energy saving was realized.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.6
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• pp.159-167
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• 2008

Cooling lubricants are used in machining operations in order to reduce friction at the tool-chip and tool-workpiece interfaces, cool both chip and tool, and remove chip. Furthermore, they influence a strong effect on the shearing mechanisms and, consequently, on the machined surface quality and tool wear. However, several researchers state that the costs related to cutting fluids is frequently higher than those related to cutting tools. Moreover, the cooling lubricants cause an increase in both worker's health and social problems related to their use and correct disposal. Therefore, many researchers have focused on the environmentally conscious machining technologies. One of the technologies is known as MQL(Minimum Quantity Lubrication) machining. In this paper, an experimental model to obtain the optimal cutting conditions in MQL turning was suggested, and the effects of cutting conditions on surface roughness and cutting force were analyzed. For these purposes, FFD (Fractional Factorial Design) and RSM (Response Surface Methods) were used for the experiment. Cutting force and surface roughness with different cutting conditions were measured through the external cylindrical turning of Al 6061 based on the experiment plan. The measured data were analyzed by regression analysis and verification experiments with random conditions were conducted to confirm the suggested experimental model.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.1059-1063
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• 2005

Development of a feed drive-system with high speed, positioning accuracy and thrust has been an important issue in modern automation systems and machine tools. Linear motors can be used as an efficient system to achieve such technical demands. By eliminating mechanical transmission mechanisms such as ball screw or rack-pinion, much higher speeds and greater acceleration can be achieved without backlash or excessive friction. However, due to great power loss and magnetic attraction of the linear motors heating and deflection problems occur. Therefore, it is necessary to design strong structure, cooling device with high efficiency and light weight construction in designing stage of linear motors. This paper presents an investigation into a structural design of linear motor system. In this research, a new concept of moving table with high stiffness and of cooling plate is also introduced. Structure analyses are performed by using a commercial code ANSYS in order to evaluate the design safety.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.560-563
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• 2005

According to the demand of the high productivity, the interest of manufacturing skills is growing in industrial society. Especially the high-speed spindle in machining center becomes important these days. The rotating accuracy of the spindle in machining center concerns the centrifugal force. In detail explaining, it is influenced by the unbalance mass. In this study, we could find changes of the vibration caused by condition (increased mass, rotating speed, position) of unbalance mass and verify it using a software - $ADAMS^(R)$ With this study, it will help workers on the spot solve the problems concerning unbalance mass.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.865-868
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• 2005

This paper presents analysis of dynamic characteristics of a high-speed milling spindle with a built-in motor. The spindle system with a built-in motor can be used to simplify the structure of machine tools. to improve tire machining flexibility of machine. tools, and to perform the high speed machining. In this system the shaft is usually assumed as a rigid rotor. In the spindle system design, it is very important to improve modal characteristics, and modal analysis is performed in the first place. Therefore in this paper, on the assumption that supporting bearings of spindle was selected most suitable condition, analyzed dynamic characteristics of a high-speed spindle according to its position. Optimal design was applicated to select most suitable position of bearings. Considered tile mass and stiffness effects of the built-in motor's rotor are analyzed by numerical method. The result shows the natural frequency of 1st bending mode of spindle.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.12
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• pp.1353-1358
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• 2011

LAT(Laser Assisted Turning) is a method that applies a machining process after softening a workpiece in which a preheating process is locally applied to its machining section using laser heat source. LAT shows several advantages, such as high productivity, reduction of manufacturing cost, high quality. Analysis of temperature distribution after preheating for LAT is very difficult due to its very small heat input area and large energy and its movement. Also, the LAT for a square bar is more difficult because the shape of a laser heat source can be changed according to the rotation of the workpiece. In this study, thermal analysis for LAT of square bar was performed using laser heat source projection method. And, the analysis results were compared with the results of the prior study of numerical calculation method. It is thus shown that the proposed method is efficient for the thermal analysis of a shaped bar.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.10
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• pp.93-98
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• 2019

Recently, with the development of the aerospace and automotive industries, the demand for high-melting-point materials has increased. However, high-melting-point materials are difficult to cut through conventional machining methods. Thermally assisted machining (TAM) is a method for improving the machinability by preheating the materials. A laser, the most commonly used device for TAM, has high efficiency through local preheating but is not sufficient for maintaining a high preheating temperature due to rapid cooling. However, the use of multi-heat sources can supplement the disadvantage of a single heat source. The high preheating temperature can be maintained with a wide and deep heat-affected zone (HAZ) by multi-heat sources. The purpose of this study is to analyze the preheating effects of multi-heat sources using laser plasma. Thermal analysis and preheating experiments were carried out. As a result, the high preheating effect of multi-heat sources compared with a single heat source was verified.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.10
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• pp.99-103
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• 2019

Recently, as the high-precision machinery industry has developed rapidly, peripheral equipment has been developed to improve machining efficiency. Peripheral equipment for machining includes cooling units, housings, oil separators, and much more. Oil, such as cleaning and cutting fluids, is used for machining. When waste oil is reused, the contamination of the workpieces and reduction in machining accuracy are generated by the waste oil, including sludge. Therefore, the development of an oil separator is necessary for efficiently separating oil, water, and sludge. The purpose of this study is to analyze the oil separation efficiency and flow characteristics of a high-speed centrifugal separator according to the rotation velocity and diffusion plate. The oil separation efficiency and flow characteristics were analyzed using hydrodynamic theory and computational fluid dynamics (CFD). The results of this study will be used as basic data for the development of a high-speed centrifugal separator.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.10
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• pp.44-51
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• 2020

We studied the heating characteristics of a whirling spindle. This spindle is an important component of a whirling machine for turning a ball screw shaft. In the manufacturing process for a conventional ball screw shaft, a single tool is used to form a spiral in a lathe machine tool. Thereafter, a high-frequency heat treatment process is performed. Recently, a whirling-type cutting method has emerged. This method can perform hard turning in the rotating direction of the spiral portion of the ball screw shaft by rotating and mounting multiple tools. The whirling method can be applied to the heat-treated material. In this study, an experimental apparatus was constructed to analyze the whirling spindle. The experiment proceeded in four steps. The rotating speed of the whirling spindle was set to ISO random and sequential rising conditions. Cooling and non-cooling modes in the cooling jacket were tested. As a result of the above experiment, the heating characteristics of the whirling spindle were derived.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.2
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• pp.45-50
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• 2021

In the recent fourth industrial revolution, the demand for additive processes has emerged rapidly in many mechanical industries, including the aircraft and automobile industries. Additive processes, in contrast to subtractive processes, can be used to produce complex-shaped products, such as three-dimensional cooling systems and aircraft parts that are difficult to produce using conventional production technologies. However, the limitations of additive processes include nonuniform surface quality, which necessitates the use of post-processing techniques such as subtractive methods and grinding. This has led to the need for hybrid machines that combine additive and subtractive processes. A hybrid machine uses additional additive and subtractive modules, so product deformation, for instance, deflection, is likely to occur. Therefore, structural analysis and design optimization of hybrid machines are essential because these defects cause multiple problems, such as reduced workpiece precision during processing. In this study, structural analysis was conducted before the development of an additive/subtractive hybrid processing machine. In addition, structural optimization was performed to improve the stability of the hybrid machine.