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Volume 30(5); May 2013

Articles
한국정밀공학회지 Vol.30 No.5 목차
J. Korean Soc. Precis. Eng. 2013;30(5):459-460.
Published online May 1, 2013
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Prediction and Evaluation Method of Energy Consumption in Machine Tools
Chan-Hong Lee, Jooho Hwang
J. Korean Soc. Precis. Eng. 2013;30(5):461-466.
Published online May 1, 2013
In this paper, main mechanism and measurement method of energy consumption for machine tools are investigated by experiment and simulation. To evaluate total energy consumption of the machine tools, standard test workpiece and measuring method and test procedures are suggested. And, improvement of energy consumption evaluation by the motion kinematics theory is used. In addition, to estimate energy consumption of machine tools in design process, mass distribution of the structure and 5 axis motions are investigated and simulated by numerical analysis.
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Design Approaches and Strategies for Energy Saving of 5-Axis Multi-Functional Machine Tools
James Kim, Kyung-Dong Kim, Chan-Hong Lee, Sung-Ho Nam
J. Korean Soc. Precis. Eng. 2013;30(5):467-473.
Published online May 1, 2013
Diverse approaches for reducing the total energy consumption of machine tools have been introduced and developed, to cope with rapid increase of total energy costs in world-wide manufacturing industries. To realize the improvement of the energy efficiency, systematic and integrated strategies must be considered, including energy-saving design, optimized control operation and concrete evaluation of the energy efficiency. This paper proposes key enabling technologies required to improve the energy efficiency of 5-axis multi-functional machining tools, considering both of system design and operation in the real production environments. Related standardized procedures of the energy efficiency evaluation is also represented.
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Lightweight of Movable Parts for Energy Reduction of 5-axis Machining Center
Myung Gyu Lee, Sung Ho Nam, Dong Yoon Lee
J. Korean Soc. Precis. Eng. 2013;30(5):474-479.
Published online May 1, 2013
Mass reduction of the machine tool movable parts is a tool for achieving lower energy demands of the machine tool operation. The realization of lightweight design in machine tool can be achieved by structural lightweight design and material lightweight design. In this study, topology optimization strategy was applied to design optimized structures of movable parts of 5 axis machining center. The weight of ram which has most significant influence on the stiffness of whole machine tool was reduced without stiffness deterioration. The redesigned optimized ram has 24.2% less weight while maintaining the same displacement caused by cutting force.
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An On-line System Architecture for Remote Energy Monitoring of CNC Machine Tools
Sung-Ho Nam, Ki-Hyeong Song, Jae-Yong Baek, Dong-Yoon Lee, Kwang-Yeol Ryu
J. Korean Soc. Precis. Eng. 2013;30(5):480-485.
Published online May 1, 2013
Enhancing energy efficiency of machine tools causes substantial impacts on the manufacturing industries, to cope with the competitive introduction of the total energy management strategies. Real-time energy monitoring is essential to identify energy consumption patterns of the machine tools and correlate them with the energy management strategy. Integrated analysis of machine tool’s operation status and the corresponding energy usage is most important to accurately evaluate the energy efficiency under the various machining process environments. This paper proposes a system architecture to realize the online energy monitoring system and the embedded energy monitoring approach interconnected with the CNC kernel. The shop-floor operation management system is presented to integrate the proposed online energy monitoring approach.
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Standby Strategies for Energy Saving in Peripheral Equipment of Machine Tools
Taejung Kim, Taeho Kim, Sungchul Jee
J. Korean Soc. Precis. Eng. 2013;30(5):486-492.
Published online May 1, 2013
Energy cost has been increasing rapidly to comply with environmental regulations worldwide and the manufacturing industry who consumes more than half of the total energy needs to improve their cost competitiveness considering environmental costs. Machine tools are essential elements in manufacturing industry and efforts have been made recently to increase their energy efficiency mainly by German and Japanese machine tool builders. In this paper, trends in energy saving technology are described on the hardware and software sides of peripheral equipment of machine tools. In addition, the power consumption of a machining center is measured and analyzed to develop a software-based standby strategy for energy saving with peripheral equipment of machine tools.
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A Study on the Optimization of Grinding Energy Density for a Non-linear Grinding System with Dual Time Delay
Jeehyun Jung, Pilkee Kim, Jung-In Lee, Sooyoung Lee, Jong-Hang Lee, Kyung-Dong Kim, Jongwon Seok
J. Korean Soc. Precis. Eng. 2013;30(5):493-498.
Published online May 1, 2013
The present study treats the optimization process for a non-linear grinding system with dual time delay, mainly from the energetic viewpoint. To this end, the stability of the grinding system is investigated first with regard to the grinding wheel rotation speed. The concept of grinding energy density is newly proposed as the primary figure of merit and this quantity is evaluated at various stable and limit cycle conditions. The computational results show that simple monotonic trend in energy density is observed under stable conditions, whilst rather complicated behaviors can appear when the conditions are associated with limit cycle oscillations. Finally, the relations between the vibration amplitude and the energy density and their implications on the engineering decision/compromise are discussed.
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Characteristics of Surface Hardening of Nd:YAG Laser According to the Diameter variation of SM45C Cylindrical Bar
Ka Ram Lee, Yun Seok Yang, Chan Youn Hwang, Eun Kyeong Park, Young Tae Yoo
J. Korean Soc. Precis. Eng. 2013;30(5):499-506.
Published online May 1, 2013
Heat-treatment is one of the core technologies to enhance various characteristics such as strength, hardness, toughness, abrasion resistance and fatigue resistance for the mold material. This paper focuses on characteristics of the laser heat-treatment according to the cylindrical bar diameter variation in case of the SM45C. From the results of the experiments, it has been observed that the maximum hardness is 744Hv when the power is 1630W and the travel of laser is 0.5m/min. And then, the hardness width, depth and microstructure were observed for characteristics. Finally, when the cylindrical bar diameter size grow, the hardness width decrease whereas hardness depth increase.
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Development and Experimental Verification of an Error Compensation Model for a Fiveaxis Machine Tool using an Error Matrix
Sung Hwan Kweon, Dong Mok Lee, Seung Han Yang
J. Korean Soc. Precis. Eng. 2013;30(5):507-512.
Published online May 1, 2013
This paper proposes a new model to compensate for errors of a five-axis machine tool. A matrix with error components, that is, an error matrix, is separated from the error synthesis model of a five-axis machine tool. Based on the kinematics and inversion of the error matrix which can be obtained not by using a numerical method, an error compensation model is established and used to calculate compensation values of joint variables. The proposed compensation model does not need numerical methods to find the compensation values from the error compensation model, which includes nonlinear equations. An experiment using a double ball-bar is implemented to verify the proposed model.
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A Yarn Process Inspection System Using Image Processing
Chang-Yong Lim, Dongwon Shin, Jang-Kyu Yoon
J. Korean Soc. Precis. Eng. 2013;30(5):513-519.
Published online May 1, 2013
Line scan camera has been widely used in the area of inspection of glass, film, fabric, iron, PCB and etc. due to the high resolution and the high speed. We developed the line scan based vision system to inspect tangled and cut-off status of yarn in the manufacturing process. The original image is binarized with a proper threshold, and the gap distances in the yarn are measured in real time, so finally the status of the process is decided by the maximum value of the gap distance. All procedures are executed in real time by realization of multi-processed threads. By implementation of this system, the error of the yarn in manufacturing process can be precedently monitored and the loss of the yarn is decreased efficiently.
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5-D.O.F. Force/moment Sensor using Optical Intensity Modulation in MR-field
Min Gyu Kim, Dong Hyeok Lee, Nahm Gyoo Cho
J. Korean Soc. Precis. Eng. 2013;30(5):520-528.
Published online May 1, 2013
A 20 mm diameter of small 5-D.O.F. force sensor has been developed for applications in MR-field Optical intensity modulation was adopted for transducing to miniaturize the sensor structure. For its accurate sensing of 5-D.O.F. force/moment, the elastic detecting module was designed to respond independently to each force or moment component. And for small size, two optical transducing modules of 2-D.O.F. and 3-D.O.F. were designed and integrated with the detecting module where optical fibers were arranged in parallel to make the sensor small. It is confirmed by calibration test that the detecting modules deforms linearly and independently to the input force. The results of evaluating test show that the range and resolution of forces are ±4 N and 0.94~7.1 mN and the range and resolution of moments are ±120 N·mm and 0.023~0.034 N·mm.
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Design of a Six-axis Force/moment Sensor for Wrist Twist-exercise Rehabilitation Robot
Hyeon Min Kim, Gab Soon Kim
J. Korean Soc. Precis. Eng. 2013;30(5):529-536.
Published online May 1, 2013
Most serious stroke patients have the paralysis on their wrists, and can’t use their hands freely. But their wrists can be recovered by rehabilitation exercises. Recently, professional rehabilitation therapeutists help stroke patients exercise their wrists in hospital. But it is difficult for them to rehabilitate their wrists, because the therapeutists are much less than stroke patients in number. Therefore, the wrist twist-exercise rehabilitation robot that can measure the twist force of the patients’ wrists is needed and developed. In this paper, the six-axis force/moment sensor was designed appropriately for the robot. As a test result, the interference error of the six-axis force/moment sensor was less than 0.85%. It is thought that the sensor can be used to measure the wrist twist force of the patient.
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Design Parametric Analysis of Radial Beam Coupling using Finite Element Analysis
Chibum Lee, Yeong Il Park
J. Korean Soc. Precis. Eng. 2013;30(5):537-543.
Published online May 1, 2013
In this paper, a novel radial beam coupling model was proposed and the design parameters were studied for the efficient transmission of torque. To develop a high performance radial beam coupling, an analytical way to predict the performance in design phase is required. One of the best ways to estimate the performance of the coupling without manufacturing is to evaluate the stress and torsional stiffness by building a finite element model with a special attention to the radial beam cutting part. For the best results of FEA, the material properties were obtained through testing. To verify the reliability of finite element model, the results of FEA were compared with the experiments. The main design parameters of radial beam cutting width, radial beam cutting depth, and radial beam cutting direction were considered for the performance of radial beam coupling.
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Flow Characteristics of Fine Particles for Separated Device Shapes
Seon Kyeong Hwang, Seoung Soo Lee, Hyo Sang Jung
J. Korean Soc. Precis. Eng. 2013;30(5):544-551.
Published online May 1, 2013
Recently high speed mixer, which is mixing, grinding, dispersion for liquid-liquid material, has been widely used several industries such as food, cosmetics, pharmaceuticals, fine chemicals, electronic material. This high speed mixer has a core element part called particle separation device. Particle separation device, which makes mixed liquid and liquid material using shear forces from a rotor and a stator, is a decisive factor in the distributed parts. In this study, we examined the velocity distribution of the two models of particle separation device using computation fluid dynamics, so that we were able to see the difference of the velocity distribution according to the shape. Also, by experiment, we observed that the use of rotor-screen type is deemed more suitable in case of accurately considering the effect of improving of the dispersibility through the circulation of the future.
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A Study on the Design of Flexible Display Considering the Failure Characteristics of ITO Layer
Min Gyu Kim, Sang Baek Park, Soo-Won Chae
J. Korean Soc. Precis. Eng. 2013;30(5):552-558.
Published online May 1, 2013
In recent years the interest on flexible display has been increasing as a future display due to its bendable characteristics. An ITO(indium tin oxide) layer, which is part of a flexible display, can be broken easily while bending because it is made of brittle materials. This brittle property can cause the malfunction of flexible display. To analyze fracture characteristics of ITO layer, bending test was conducted commonly. However, it is not possible to know specific phenomena on bended ITO layer by simple bending test only. Accordingly, in this study, the FE(finite element) model is developed similarly to a real flexible display to analyze stress distribution of flexible display under bending condition, especially on ITO layer. To validate FE model, actual bending test was conducted and the test results were compared with the simulation results by measuring reaction forces during bending. By using the developed model, FE analysis about the effect of design parameter (Thickness & Young’s Modulus of BL) on ITO Layer was performed. By explained FE analysis above, this research draws a conclusion of reliable design guide of flexible display, especially on ITO layer.
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