• Journal of Korean Society of Industrial and Systems Engineering
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• v.38 no.4
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• pp.177-183
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• 2015

Incremental sheet metal forming is a manufacturing process to produce thin parts using sheet metals by a series of small incremental deformation. The process rarely needs dedicated dies and molds, thus, preparation time for the process is relatively short as to be compared to conventional metal forming. Spring back in sheet metal working is very common, which causes critical errors in dimensions. Incremental sheet metal forming is not fully investigated yet. Hence, incremental sheet metal forming frequently produces inaccurate parts. This paper proposes a method to minimize dimensional errors to improve shape accuracy of products manufactured by incremental forming. This study conducts experiments using an exclusive incremental forming machine and the material for these experiments are sheets of aluminum AL1015. This research defines a process parameter and selects a few factors for the experiments. The parameters employed in this paper are tool feed rate, tool diameter, step depth, material thickness, forming method, dies applied, and tool path method. In addition, their levels for each factor are determined. The plan of the experiments is designed using orthogonal array $L_8$ ($2^7$) which requires minimum number of experiments. Based on the measurements, dimensional errors are collected both on the tool contacted surfaces and on the non-contacted surfaces. The distances between the formed surfaces and the CAD models are scanned and recorded using a commercial software product. These collected data are statistically analyzed and ANOVAs (analysis of variances) are drawn up. From the ANOVAs, this paper concludes that the process parameters of tool diameter, forming depth, and forming method are the significant factors to reduce the errors on the tool contacted surface. On the other hand, the experimental factors of forming method and dies applied are the significant factors on the non-contacted surface. However, the negative forming method always produces better accuracy than the positive forming method.

• International Area Studies Review
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• v.13 no.3
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• pp.213-238
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• 2009

This paper empirically examines effects of exporting on employment over the period 2000-2007 for Korean listed and non-listed manufacturing firms. The paper employs the dynamic panel model of labor demand and controls for simultaneity of the exports and real wages using a two step random effect Tobit-DPD (Dynamic Panel Data) procedure. Our empirical results suggest that surprisingly, there is no robust evidence for employment effects of exporting of Korea's large firms and small-medium sized firms during the sample period after Korean financial crisis. This implies that Korean exporting patterns have been changed in a way that exporting highly capital intensive goods leads to importing more intermediate goods and thus to countervailing the employment effects of exporting. This suggests that expansion of exporting by lowering exporting prices through the bilateral FTA might not be helpful to enhancing employment in Korea.

• Design & Manufacturing
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• v.13 no.1
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• pp.5-12
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• 2019

In this paper, we studied the micro tool deflection, micro cutting with low temperature, and deformation of micro ribs caused by cutting forces. First, we performed an integrated machining error compensation method based on captured images of tool deflection shapes in micro cutting process. In micro cutting process, micro tool deflection generates very serious problems in contrast to macro tool deflection. To get the real images of micro tool deflection, it is possible to estimate tool deflection in cutting conditions modeled and to compensate for machining errors using an iterative algorithm correcting tool path. Second, in macro cutting fields, the cryogenic cutting process has been applied to cut the refractory metal but, the serious problem may be generated in micro cutting fields by the cryogenic environment. However, if the proper low temperature is applied to micro cutting area, the cooling effect of cutting heat is expected. Such effect can make the reduction of tool wear and burr formation. For verifying this passibility, the micro cutting experiment at low temperature was performed and SEM images were analyzed. Third, the micro pattern was deformed by the cutting forces and the shape error occurred in the sidewall multi-step cutting process were minimized. As the results, the relationship between the cutting conditions and the deformation of micro-structure during micro cutting process was investigated.

• Journal of Climate Change Research
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• v.4 no.3
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• pp.269-278
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• 2013

Sulfur hexafloride($SF_6$) emission to atmosphere is lower than $CO_2$, but $SF_6$ GWP is 22,800 times lager than $CO_2$. In recent years as restriction of $non-CO_2$ gas has been greatly reinforced, development of environment-friendly technology with $SF_6$ removal is becoming to main issue. This study shows that $SF_6$ used insulator electrical equipment has emission characteristics during the each phase(maintenance, use, diposal), and analyzed $SF_6$ emission reduction technology related phase. The major technology applies maintenance and disposal step is that improvment of gas recovery rate($85{\rightarrow}99%$), manufacturing catalysts, internal inspection of circuit breaker using endoscopy. Using those technolgies can reduce $SF_6$ emission in atmosphere.

• Advances in aircraft and spacecraft science
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• v.6 no.2
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• pp.145-156
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• 2019

As the industrial desire for a step change in productivity within the manufacture of composite structures increases, so does the interest in Through-Thickness Reinforcement technologies. As manufacturers look to increase the production rate, whilst reducing cost, Through-Thickness Reinforcement technologies represent valid methods to reinforce structural joints, as well as providing a potential alternative to mechanical fastening and bolting. The use of tufting promises to resolve the typically low delamination resistance, which is necessary when it comes to creating intersections within complex composite structures. Emerging methods include the use of 3D woven connectors, and orthogonally intersecting fibre packs, with the components secured by the selective insertion of microfasteners in the form of tufts. Intersections of this type are prevalent in aeronautical applications, as a typical connection to be found in aircraft wing structures, and their intersections with the composite skin and other structural elements. The common practice is to create back-to-back composite "L's", or to utilise a machined metallic connector, mechanically fastened to the remainder of the structure. 3D woven connectors and selective Through-Thickness Reinforcement promise to increase the ultimate load that the structure can bear, whilst reducing manufacturing complexity, increasing the load carrying capability and facilitating the automated production of parts of the composite structure. This paper provides an overview of the currently available methods for creating intersections within composite structures and compares them to alternatives involving the use of 3D woven connectors, and the application of selective Through-Thickness Reinforcement for enhanced damage tolerance. The use of tufts is investigated, and their effect on the load carrying ability of the structure is examined. The results of mechanical tests are presented for each of the methods described, and their failure characteristics examined.

• Journal of the Korean Society of Industry Convergence
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• v.21 no.6
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• pp.265-271
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• 2018

DC-DC buck converter is a critical building block in the power management integrated circuit (PMIC) architecture for the portable devices such as cellular phone, personal digital assistance (PDA) because of its power efficiency over a wide range of conversion ratio. To ensure a safe operation, avoid unexpected damages and enhance the reliability of the converter, fully-integrated protection circuits such as over voltage protection (OVP), under voltage lock out (UVLO), startup, and thermal shutdown (TSD) blocks are designed. In this paper, these three fully-integrated protection circuit blocks are proposed for use in the DC-DC buck converter. The buck converter with proposed protection blocks is operated with a switching frequency of 1 MHz in continuous conduction mode (CCM). In order to verify the proposed scheme, the buck converter has been designed using a 180 nm CMOS technology. The UVLO circuit is designed to track the input voltage and turns on/off the buck converter when the input voltage is higher/lower than 2.6 V, respectively. The OVP circuit blocks the buck converter's operation when the input voltage is over 3.3 V, thereby preventing the destruction of the devices inside the controller IC. The TSD circuit shuts down the converter's operation when the temperature is over $85^{\circ}C$. In order to verify the proposed scheme, these protection circuits were firstly verified through the simulation in SPICE. The proposed protection circuits were then fabricated and the measured results showed a good matching with the simulation results.

• Food Engineering Progress
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• v.21 no.1
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• pp.12-21
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• 2017

Foods are becoming more customized and consumers demand food that provides great taste and appearance and that improves health. Food three-dimensional (3D)-printing technology has a great potential to manufacture food products with customized shape, texture, color, flavor, and even nutrition. Food materials for 3D-printing do not rely on the concentration of the manufacturing processes of a product in a single step, but it is associated with the design of food with textures and potentially enhanced nutritional value. The potential uses of food 3D-printing can be forecasted through the three following levels of industry: consumer-produced foods, small-scale food production, and industrial scale food production. Consumer-produced foods would be made in the kitchen, a traditional setting using a nontraditional tool. Small-scale food production would include shops, restaurants, bakeries, and other institutions which produce food for tens to thousands of individuals. Industrial scale production would be for the mass consumer market of hundreds of thousands of consumers. For this reason, food 3D-printing could make an impact on food for personalized nutrition, on-demand food fabrication, food processing technologies, and process design in food industry in the future. This article review on food materials for 3D-printing, rheology control of food, 3D-printing system for food fabrication, 3D-printing based on molecular cuisine, 3D-printing mobile platform for customized food, and future trends in the food market.

• Design & Manufacturing
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• v.15 no.4
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• pp.24-31
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• 2021

In this study, an artificial neural network model was constructed to convert CAE analysis data into similar experimental data. In the analysis and experiment, the injection molding data for 50 conditions were acquired through the design of experiment and random selection method. The injection molding conditions and the weight, height, and diameter of the product derived from CAE results were used as the input parameters for learning of the convert model. Also the product qualities of experimental results were used as the output parameters for learning of the convert model. The accuracy of the convert model showed RMSE values of 0.06g, 0.03mm, and 0.03mm in weight, height, and diameter, respectively. As the next step, additional randomly selected conditions were created and CAE analysis was performed. Then, the additional CAE analysis data were converted to similar experimental data through the conversion model. An artificial neural network model was constructed to predict the quality of injection molded product by using converted similar experimental data and injection molding experiment data. The injection molding conditions were used as input parameters for learning of the predicted model and weight, height, and diameter of the product were used as output parameters for learning. As a result of evaluating the performance of the prediction model, the predicted weight, height, and diameter showed RMSE values of 0.11g, 0.03mm, and 0.05mm and in terms of quality criteria of the target product, all of them showed accurate results satisfying the criteria range.

• Journal of Korea Trade
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• v.24 no.7
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• pp.54-72
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• 2020

Purpose - This study explores the contextual factors that affect the relationship between CEO overseas experience and firm internationalization. This study incorporates a wide range of contextual factors, including mega, macro, and micro variables. In particular, this study goes a step further from prior studies by incorporating a higher-order variable i.e., the global financial crisis that can constrain the managerial discretion of a CEO. Design/methodology - To structure the balanced data set before and after the 2008 global financial crisis, we used the data for the years from 2002 to 2014 from a sample of Korean manufacturing firms. Ultimately, 1101 firm-year unbalanced panel observations from 101 firms were used for the analysis. Findings - Our main findings can be summarized as follows. CEO overseas experience is positively related to firm internationalization. However, this relationship varies depending on the CEOs level of managerial discretion. As for the constraining moderation, the global financial crisis weakened the positive relationship between CEO overseas experience and firm internationalization. As for the enabling moderation, the CEOs tenure strengthened the relationship. Originality/value - This study adopted the knowledge, skills, and abilities (KSA) framework to explain the relationship between CEO overseas experience and firm internationalization. Moreover, we argue that the CEO-internationalization relationship depends on the specific context of the managerial discretion, focusing on the 2008 global financial crisis. Empirically, this study adopted the 2SLS procedure to correct endogeneity. Instead of taking the actual value of prior internationalization as a control, we estimated prior internationalization using the instrument variables at an industry level. This procedure made our estimation more robust.

• Journal of the Semiconductor & Display Technology
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• v.20 no.4
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• pp.171-176
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• 2021

Die-to-wafer (D2W) hybrid bonding in the multilayer semiconductor manufacturing process is one of wafer direct bonding, and various studies are being conducted around the world. A noteworthy point in the current die-to-wafer process is that a lot of voids occur on the bonding surface of the die during bonding. In this study, as a suggested method for removing voids generated during the D2W hybrid bonding process, a flexible mechanism for implementing convex for die bonding to be applied to the bond head is proposed. In addition, modeling of flexible mechanisms, analysis/design/control/evaluation of static/dynamics properties are performed. The proposed system was controlled by capacitive sensor (lion precision, CPL 290), piezo actuator (P-888,91), and dSpace. This flexure mechanism implemented a working range of 200 ㎛, resolution(3σ) of 7.276nm, Inposition(3σ) of 3.503nm, settling time(2%) of 500.133ms by applying a reverse bridge type mechanism and leaf spring guide, and at the same time realized a maximum step difference of 6 ㎛ between die edge and center. The results of this study are applied to the D2W hybrid bonding process and are expected to bring about an effect of increasing semiconductor yield through void removal. In addition, it is expected that it can be utilized as a system that meets the convex variable amount required for each device by adjusting the elongation amount of the piezo actuator coupled to the flexible mechanism in a precise unit.