• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.10
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• pp.50-55
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• 2021

In this study, to create circular holes on an inclined conic face, we developed a novel process of vertical piercing on the plane before drawing, instead of applying an expensive cam-piercing method. The pierced holes are deformed during the drawing, and their shapes are affected by the size of the center hole. Using the Abaqus CAE program, the deformation tendency of the holes, according to the diameter of the center hole, was identified, and the diameter for securing the roundness of the side holes were determined through actual experiments. The developed process was successfully applied to mass production of the part, and a cost reduction is expected.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.349-355
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• 2017

Bending work using press dies involves bending a flat blank to a desired angle. The bending produces a flange (the bent part) and a web (the unbent part). The bending line will have a bending angle, and there is an inner and outer bending radius. The minimum inner radius size is determined by the material used. When the inner radius size is too small, there will be excess metal welding, which will cause a crack in the outer radius part. The outer bending radius size cannot be controlled by a bending punch and die block. Types of bending include V-bending, U-bending, O-bending, edge bending, twist bending, and crimping. Z-bending involves two bending lines, which are set on the upper side and under surface of the blank, respectively, and upward or downward bending is used. Z-bending is also called crank bending. Z-bending using this type of die structure will produce a standard inner bending radius. The standard size is the minimum bending radius that represents the angle radius of the bending punch. In industry, there is a need for a sharp edge shape with a very small size (R=0.2mm), but that is not possible when using bending punch and die block. The purpose of this research is to meet the need by development.

• Journal of Powder Materials
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• v.27 no.3
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• pp.256-267
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• 2020

Metal additive manufacturing (AM) technologies are classified into two groups according to the consolidation mechanisms and densification degrees of the as-built parts. Densified parts are obtained via a single-step process such as powder bed fusion, directed energy deposition, and sheet lamination AM technologies. Conversely, green bodies are consolidated with the aid of binder phases in multi-step processes such as binder jetting and material extrusion AM. Green-body part shapes are sustained by binder phases, which are removed for the debinding process. Chemical and/or thermal debinding processes are usually devised to enhance debinding kinetics. The pathways to final densification of the green parts are sintering and/or molten metal infiltration. With respect to innovation types, the multi-step metal AM process allows conventional powder metallurgy manufacturing to be innovated continuously. Eliminating cost/time-consuming molds, enlarged 3D design freedom, and wide material selectivity create opportunities for the industrial adoption of multi-step AM technologies. In addition, knowledge of powders and powder metallurgy fuel advances of multi-step AM technologies. In the present study, multi-step AM technologies are briefly introduced from the viewpoint of the entire manufacturing lifecycle.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.2
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• pp.55-61
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• 2013

The horn is a key part of the ultrasonic welder. As the shape, mass and material of a horn have effects on the resonant frequency and the vibration mode in ultrasonic welding, a horn has to be designed and manufactured accurately. In this study, 40kHz band horn was designed and manufactured through the vibration mode and finite element analysis. A result of modal analysis showed that the natural frequency of the horn was 39,794Hz, and the frequency response by a harmonic response analysis was 39,800Hz - close to the intended frequency, 40kHz. In addition, weldability of the developed horn was estimated by welding of two Ni sheets and tensile-shear test of welded samples. It was shown the developed horn could be used in metal sheet welding.

• Transactions of Materials Processing
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• v.19 no.8
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• pp.508-516
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• 2010

Thickening process in sheet metal forming is being increased to improve the strength as well as to reduce manufacturing process such as welding. This process can make it possible to obtain part locally thicker than that of initial sheet thickness. In this study, design method for manufacturing the component which has double sinks with local thickened wall is proposed. Deep drawing and upsetting processes are applied in order to form double sinks and thicken its walls. Used material is SPHC440 with the thickness of 2.0mm and initial blank size is determined on the basis of the final product. Distance between the center of double sinks and first drawing ratio to avoid fracture are the most significant factors during deep drawing. FE-analysis is implemented in order to determine the appropriate values. Progressive die is designed based on the proposed method and FE-analysis. As a result of experiment, locally thickened component can be manufactured, which has double sinks with the thickness about 3mm at the corner and wall.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.26 no.4
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• pp.425-429
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• 2017

During ultrasonic welding, plastic deformation, elastic hysteresis, and friction generate heat at the contact portions of the two materials to be welded, theoretically analyzing and experimentally measuring the temperature at the welded part are very important for identifying the heat affected zone. However, the welding temperature during ultrasonic welding wherein welding is performed in less than a second is a challenge. We investigated the effects of welding conditions such as welding time, welding pressure, and the ultrasonic vibration amplitude of horns on the temperature of welded surface of a Ni sheet of thickness 0.1 mm. We used a horn with a resonance frequency of 40 kHz and an ultrasonic welder. The temperature was measured using a intrared sensor, and its characteristics were investigated. Experimental results showed that increase in welding time and pressure and ultrasonic vibration amplitude of horns generally caused the increase in surface temperature of the weld.

• Transactions of Materials Processing
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• v.12 no.8
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• pp.710-717
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• 2003

The implicit, finite element analysis program for analyzing the springback in the warm forming process of aluminum alloy sheets was developed. For the description of planar anisotropy in warm forming temperatures, Barlat's yield function is employed, and the power law type constitutive equation is used in terms of working temperatures for the depiction of work hardening in high temperatures. Also, Jetture's 4-node shell elements are introduced for reflecting the mechanical behavior of aluminum alloy sheet and the non-steady heat balance equations are solved for considering heat gain and loss during the forming process. For the springback evaluation, Newton-Raphson iteration method is introduced for overcoming the geometric nonlinearlity problem. In order to verify the validity of the FEM program developed, the stretching bending and springback processes are simulated. Though springback analysis results are slightly bigger than experimental ones, they have the same trend of the decreasing springback as the forming temperature increases.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.08a
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• pp.13-20
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• 2003

The implicit, finite element analysis program for analyzing the springback in the warm forming process of aluminum alloy sheets was developed. For the description of planar anisotropy in warm forming temperatures, Barlat's yield function is employed, and the power law type constitutive equation is used in terms of working temperatures fur the depiction of work hardening in high temperatures. Also, Jetture's 4-node shell elements are introduced for reflecting the mechanical behavior of aluminum alloy sheet and the non-steady heat balance equations are solved for considering heat gain and loss during the forming process. For the springback evaluation, Newton-Raphson iteration method is introduced for overcoming the geometric nonlinearlity problem. In order to verify the validity of the FEM program developed, the stretching bending and springback processes are simulated. Though springback analysis results are slightly bigger than experimental ones, they have the same trend of the decreasing springback as the forming temperature increases.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.379-382
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• 2007

The MEMS (Micro Electro Mechanical Systems) process is used in a micro/nano pattern manufacturing method. This method is based on the lithography technology. But the MEMS process has some problems such as complicated process, long processing time and high production costs. Many researchers are doing research in substitute manufacturing method to work out a solution to these problems. In this paper, we apply a dieless incremental forming technology to a substitute method of MEMS process. This dieless forming technology is using in the commercial scale sheet forming such as a prototype of automobile sheet parts. 5-axes CNC (Computerized Numeric Control) method are applied in this system to get a micro-scale dieless forming results. These 5-axes system are composed of precision AC servo motor stages (4-axes) and PZT actuator (1-axis). A PZT actuator is used in a precision actuating axis because it can be operated in the nano scale stroke resolution. This micro dieless incremental forming system has the advantage of minimization in manipulating distance and working space. As equipment and tools become smaller in size, minute inertia force and high natural frequency can be obtained. Therefore, high precision forming performance can be obtained. This allows the factory to quickly provide the customer with goods because the manufacturing system and process are reduced. To construct this micro manufacturing system, many technologies are necessary such as high stiffness frame, high precision actuating part, structural analysis, high precision tools and system control. To achieve the optimal forming quality, the micro dieless forming system is designed and made with high stiffness characteristic.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.1 no.2
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• pp.21-26
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• 2000

Flow forming is a chipless metal forming method for axi-symmetric parts, which is more economical. efficient and versatile method of producing parts than the other sheet metal forming process such as stamping or deep drawing. In this study, flow forming process with 1-Roller is applied to produce auto-transmission parts of automobiles which have been produced by Press drawing process so far. It can be known that flow forming process is applicable to the flexible manufacturing system due to the low cost for the establishment and it can be combined with press forming process to promote productivity and to improve the accuracy of products.