• Transactions of Materials Processing
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• v.22 no.5
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• pp.243-249
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• 2013

The multi-point forming (MPF) process for three-dimensional curved sheet metal has been developed as an alternative to the conventional die forming process since MPF allows the manufacturing of various shapes using one die set and reduce the cost of production. However, the MPF process cannot provide high quality products yet due to defects occurring in the sheet such as dimples and wrinkles. It can also lead to economic loss because of long tool setup time and additional machining required outside of the sheet formed area. In this study, a new sheet metal forming method, called flexible roll forming (FRF), is proposed to solve the problems of existing processes for three-dimensional curved sheet metal. This progressive process utilizes adjusting rods, as well as upper and lower flexible rollers as forming tools. In contrast with the existing processes, FRF can reduce the additional production costs because of the possible blank size for the part longitudinal direction, which is unrestricted. In this research, methods and procedures of the flexible roll forming technology are described. Numerical forming simulations of representative three-dimensional curved sheet products are also carried out to demonstrate the feasibility of this technology.

• Journal of Digital Convergence
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• v.11 no.11
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• pp.169-175
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• 2013

Smart flexible work has been a topic of considerable interest to researchers, practitioners, and public policy advocates as a tool to help individuals manage work and family roles. In this study, we investigated the types of smart flexible work arrangement and analyzed the organizational units associated with it. We found that the critical success factors of smart flexible work and the specific types of flexibility make a difference in the effects found. And we proposed on the direction of policy promotion that can contribute to the introduction of smart flexible work.

• Journal of Korean Institute of Industrial Engineers
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• v.20 no.2
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• pp.19-30
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• 1994

Generally, a planning problem in a flexible manufacturing system is considered to be a composite of three interdependent tasks : part selection, loading, and routing mix. This research presents a mathematical model which can concurrently solve part selection, loading, and routing mix problems, so the problems that are caused by treating the planning problems independently are solved. The mathematical model is aimed to minimize system unbalance and the number of late parts, including constraints such as machine capacity, tool magazine capacity, and tool inventory. To illustrate the application of the model, an example is included. Solution procedure based on Lagrangian relaxation is also suggested for larger-sized problems.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.1245-1248
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• 1996

This paper describes a cell programming environment that deals with problems associated with programming Flexible Manufacturing Cells(FMCs). The environment consists of the cell programming editor and the automatic generation module. In the cell programming editor, cell programmers can develop cell programs using task level description set which supports task-oriented specifications for manipulation cell activities. This approach to cell programming reduces the amount of details that cell programmers need to consider and allows them to concentrate on the most important aspects of the task at hand. The automatic generation module is used to transform task specifications into executable programs used by cell constituents. This module is based on efficient algorithm and expert systems which can be used for optimal path planning of robot operations and optimal machining parameters of machine tool operations. The development tool in designing the environment is an object-oriented approach which provides a simple to use and intuitive user interface, and allows for an easy development of object models associated with the environment.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.26-29
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• 1999

The sectional forming analysis program for analyzing the hydroforming processes of axisymmetric sheet parts was tleveloped. The rigid-viscoplastic FEM formulation based on membrane theory was derived, wh~cta simi~ltaneously solve force equilibrium as well as non-penetration condition. Hill's non-quadratic normal anisotropic yield theory(1979) was used for material behaviour. For describing the liquid pressure iaction, the flexible tool concept was introduced. Isotropic hardening law was also assumed. To verify the \,alidity of the formulation, the stepped cup forming process as well as the hydrostatic bulging test were \imnlated. Simulation results agreed well with Finckenstein and experimental ones.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10a
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• pp.508-513
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• 1990

오늘날, 생산성 증대와 품질 향상을 목적으로 산업용 로봇의 사용이 증대되면서 다양한 생산현장에서의 유연성과 적응성이 크게 요구되고 있는 실정이다. 그러나, 현재의 산업용 로봇은 end-effector의 dexterity의 부족으로 그 사용에 제한을 받고 있다. 이를 해결하기 위해 다지(multi-fingered), 다관절(articulated) 로봇손(robotic hands)의 도입이 필요하게 되었는데 이는 전체 로봇시스템의 능력과 유연성을 증가시킬 수 있을 것이다. 현재의 Flexible Manufacturing Workcell은 보통 한 대의 로봇팔과 많은 특수 용도의 고가의 tool로 구성되어 있으나 일반적인 모든 작업에 제한없이 모두 적용하기는 매우 어렵다. 그러므로, 다지, 다관절 로봇손의 개발 및 그 지능 제어의 실현은 작업에 따르는 불필요한 tool의 교환을 방지하여 비용과 시간을 절약함으로써 생산성을 극대화시킬 수 있다. 따라서, 본 연구에서는 Flexible Automation을 위한 다지, 다관절 로봇손의 설계 및 제작에 관한 방법을 제시하고자 한다.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.03a
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• pp.209-213
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• 1998

This study considers flowshop scheduling problem related to flexible maufacturing cell in which consists of two machining centers, robots for loading/unloading, and an automated guided vehicle(AGV) for material handling between two machining centers. Because no machinng center has buffer storage for work in process, a machining center can not release a finished job until the empty AGV is available at that machining center. While the AGV cannot tranfer an unfinished job to a machining center until the machining center empty. In this paper, an new heuristic algorithm is given to find the sequence that minimize their makespan.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.3
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• pp.1067-1082
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• 1991

본 연구에서는 비교적 강성이 약한 볼 엔드밀 공구에 있어서 처짐으로 인한 그 가공 특성을 알기 위하여, 변화된 칩 두께 및 처짐 모델로부터 절삭력을 예측하며 또한 절삭력에 의한 공구의 처짐으로 인하여 공구의 플랭크 부위와 공작물간의 발생하 는 간섭 특성을 고찰하고, 이러한 특성이 절삭성과 가공 오차에 미치는 영향을 실험을 통하여 분석하여 본다.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.115-116
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• 2012

The demand for flexible electronic systems such as wearable computers, E-paper, and flexible displays has increased due to their advantages of excellent portability, conformal contact with curved surfaces, light weight, and human friendly interfaces over present rigid electronic systems. This seminar introduces three recent progresses that can extend the application of high performance flexible inorganic electronics. The first part of this seminar will introduce a RRAM with a one transistor-one memristor (1T-1M) arrays on flexible substrates. Flexible memory is an essential part of electronics for data processing, storage, and radio frequency (RF) communication and thus a key element to realize such flexible electronic systems. Although several emerging memory technologies, including resistive switching memory, have been proposed, the cell-to-cell interference issue has to be overcome for flexible and high performance nonvolatile memory applications. The cell-to-cell interference between neighbouring memory cells occurs due to leakage current paths through adjacent low resistance state cells and induces not only unnecessary power consumption but also a misreading problem, a fatal obstacle in memory operation. To fabricate a fully functional flexible memory and prevent these unwanted effects, we integrated high performance flexible single crystal silicon transistors with an amorphous titanium oxide (a-TiO2) based memristor to control the logic state of memory. The $8{\times}8$ NOR type 1T-1M RRAM demonstrated the first random access memory operation on flexible substrates by controlling each memory unit cell independently. The second part of the seminar will discuss the flexible GaN LED on LCP substrates for implantable biosensor. Inorganic III-V light emitting diodes (LEDs) have superior characteristics, such as long-term stability, high efficiency, and strong brightness compared to conventional incandescent lamps and OLED. However, due to the brittle property of bulk inorganic semiconductor materials, III-V LED limits its applications in the field of high performance flexible electronics. This seminar introduces the first flexible and implantable GaN LED on plastic substrates that is transferred from bulk GaN on Si substrates. The superb properties of the flexible GaN thin film in terms of its wide band gap and high efficiency enable the dramatic extension of not only consumer electronic applications but also the biosensing scale. The flexible white LEDs are demonstrated for the feasibility of using a white light source for future flexible BLU devices. Finally a water-resist and a biocompatible PTFE-coated flexible LED biosensor can detect PSA at a detection limit of 1 ng/mL. These results show that the nitride-based flexible LED can be used as the future flexible display technology and a type of implantable LED biosensor for a therapy tool. The final part of this seminar will introduce a highly efficient and printable BaTiO3 thin film nanogenerator on plastic substrates. Energy harvesting technologies converting external biomechanical energy sources (such as heart beat, blood flow, muscle stretching and animal movements) into electrical energy is recently a highly demanding issue in the materials science community. Herein, we describe procedure suitable for generating and printing a lead-free microstructured BaTiO3 thin film nanogenerator on plastic substrates to overcome limitations appeared in conventional flexible ferroelectric devices. Flexible BaTiO3 thin film nanogenerator was fabricated and the piezoelectric properties and mechanically stability of ferroelectric devices were characterized. From the results, we demonstrate the highly efficient and stable performance of BaTiO3 thin film nanogenerator.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.06a
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• pp.68-75
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• 2000

The development of flexible automation in the manufacturing industry is concerned with production activities performed by unmanned machining system. A major topic relevant to metal-cutting operations is monitoring tool wear, which affects process efficiency and product quality, and implementing automatic tool replacements. In this paper, the measurement of the cutting force components has been found to provide a method for an in-process detection of tool wear. Cutting force components are divided into static and dynamic components in this paper, and the static components of cutting force have been used to detect flank wear. To eliminate the influence of variations in cutting conditions, tools, and workpiece materials, the force modeling is performed for various cutting conditions. The normalized force disparities are defined in this paper, and the relationships between normalized disparity and flank wear are established. Finally, Artificial neural network is used to learn these relationships and detect tool wear. According to the proposed method, the static force components could provide the effective means to detect flank wear for varying cutting conditions in turning operation.