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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Society for Precision Engineering
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Journal DOI :
Korean Society of Precision Engineering
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Volume & Issues
Volume 32, Issue 12 - Dec 2015
Volume 32, Issue 11 - Nov 2015
Volume 32, Issue 10 - Oct 2015
Volume 32, Issue 9 - Sep 2015
Volume 32, Issue 8 - Aug 2015
Volume 32, Issue 7 - Jul 2015
Volume 32, Issue 6 - Jun 2015
Volume 32, Issue 5 - May 2015
Volume 32, Issue 4 - Apr 2015
Volume 32, Issue 3 - Mar 2015
Volume 32, Issue 2 - Feb 2015
Volume 32, Issue 1 - Jan 2015
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Dynamic Analysis of Spindle Supported by Multiple Bearings of Different Types
Tong, Van-Canh ; Bae, Gyu-Hyun ; Hong, Seong-Wook ;
Journal of the Korean Society for Precision Engineering, volume 32, issue 2, 2015, Pages 117~125
DOI : 10.7736/KSPE.2015.32.2.117
This paper presents a dynamic modeling method for the indeterminate spindle-bearing system supported by multiple bearings of different types. A spindle-bearing system supported by ball and cylindrical roller bearings is considered. The de Mul`s bearing model is extended for calculating ball and cylindrical roller bearing stiffness matrices with inclusion of centrifugal force and gyroscopic moment. The dependence between spindle shaft reaction forces and bearing stiffness is effectively resolved using an iterative approach. The spindle rotor dynamics is established with the Timoshenko beam theory based finite elements. The spindle reaction forces, bearings stiffness and spindle natural frequencies are obtained with taking into account spindle radial load, ball bearing axial preload and rotational speed effects. The developed method is verified by comparing the simulation results with those from a commercial program.
Estimation of Rotational Motion Accuracy for Rotary Units
Hwang, Jooho ; Shim, Jongyoup ; Park, Chun-Hong ;
Journal of the Korean Society for Precision Engineering, volume 32, issue 2, 2015, Pages 127~133
DOI : 10.7736/KSPE.2015.32.2.127
The error motion of a machine tool spindle directly affects the surface errors of machined parts. Those are usually due to the imperfectness of bearings, stiffness of spindle, assembly errors, external force or unbalance of rotors. The error motions of the spindle have been needed to be decreased to desired goal of spindle`s performance. The level of error motion is needed to be estimated during the design and assembly process of the spindle. In this paper, the estimation method for the five degree of freedom (5 D.O.F) error motions for rotary units such as a spindle and rotary table are suggested. To estimate the error motions of the rotary unit, waviness of bearings and external force model were used as input data. The estimation model considers geometric relationship and force equilibrium of the five degree of the freedom motions.
Experimental Investigation for Rotational Error Motion Simulation of Inherently Compensated Aerostatic Journal Bearing
Shim, Jongyoup ; Hwang, Jooho ; Park, Chun-Hong ;
Journal of the Korean Society for Precision Engineering, volume 32, issue 2, 2015, Pages 135~140
DOI : 10.7736/KSPE.2015.32.2.135
It is an important thing for a designer to simulate and predict the performance of a spindle and a rotary table. In addition to the general performance such as static stiffness, the error motion performance information is beneficial to the designer in many cases. However for an aerostatic bearing the fluid film physical status should be calculated in order to simulate those performances and the calculation time is another obstacle for a simple performance simulation. In this paper the investigation on experiment and simulation is performed in order to find a more effective simulation method for the rotational error motion.
Thermal Characteristic Analysis of Induction Motors for Machine Tool Spindle for Motion Error Prediction
Seong, Ki-Hyun ; Cho, Han-Wook ; Hwang, Jooho ; Shim, Jongyoub ;
Journal of the Korean Society for Precision Engineering, volume 32, issue 2, 2015, Pages 141~147
DOI : 10.7736/KSPE.2015.32.2.141
This paper deals with thermal characteristic analysis of induction motors for machine tool spindle for motion error prediction. Firstly, the inverse design of general induction motors for machine tool spindle has been performed by design principles. Characteristics considering VVVF inverter of induction motors were analyzed. Secondary, power loss and thermal characteristics of induction motors analyzed by equivalent thermal resistance model from Motor-CAD S/W. To develop a second-order fitted power-loss distribution model for the constant-torque operating range of the induction motor, we employed the design of experiment and response surface methodology techniques. Finally, the analysis results were experimentally verified, and the validity of the proposed analysis method was confirmed.
Study on the Frictional Torque in the Angular Contact Ball Bearing for Machine Tool Spindle by Empirical Formula
Kim, Kang Seok ; Hwang, Jooho ; Lee, Deug Woo ; Lee, Sang Min ; Lee, Seung Jun ;
Journal of the Korean Society for Precision Engineering, volume 32, issue 2, 2015, Pages 149~157
DOI : 10.7736/KSPE.2015.32.2.149
Ball and roller bearings are commonly used machine elements for supporting rotating motion about shafts in simple devices including bicycles, in-line skates, and electric motors, as well as in complex machines. Heat is generated by the friction in the bearings, which causes the temperature inside the bearing to increase. If the heat is not appropriately removed from the bearing, elevated temperatures may give rise to premature failure. It is, therefore, important to be able to calculate the temperature in the bearings due to friction.Here, we describe a method to estimate the frictional torque in bearings using an empirical formula developed using a method based on bearing analysis tool and the measured frictional torque in a spindle system. Thermal analysis of the spindle system including the bearings was achieved using the finite element method (FEM), and the bearing temperature was compared with measured data to verify the empirical formula.
Parameter Analysis for the Lateral Thickness of the Coated Layer to Improve Product Quality in Large Area Roll-to-Roll Slot-Die Coating Process
Park, Janghoon ; Lee, Changwoo ;
Journal of the Korean Society for Precision Engineering, volume 32, issue 2, 2015, Pages 159~166
DOI : 10.7736/KSPE.2015.32.2.159
Slot-die coating is well known technique to guarantee a uniformly coated layer and is compatible with roll-to-roll process. In actual roll-to-roll slot-die coating process, the lateral difference of coated layer thickness is observed. An experimental study was performed to improve the coating quality. Coating speed and coating gap were selected as the experimental factors. A full factorial, statistical method was conducted to optimize the process conditions. Based on the results of repeated experiment, the lowest deviation of lateral thickness (700 nm, <10%) was achieved at 10 m/min coating speed and
coating gap. This result has significance because such optimized process guideline can be utilized with all process improvement in various coating applications.
Analysis of Induction Heating according to Coil Shapes on the V-groove Weld Joint
Ahn, Soo Deok ; Cho, Young Tae ; Jung, Yoon Gyo ;
Journal of the Korean Society for Precision Engineering, volume 32, issue 2, 2015, Pages 167~172
DOI : 10.7736/KSPE.2015.32.2.167
In order to prevent crack in thick weld zones, the preheating process such as induction and gas torch heating needs to be applied. Among them induction heating is the most effective heat source because it has rare thermal effect and very rapid heating characteristics. In this paper, when the induction heating method is used to improve arc welding, the temperature distribution and magnetic field density of the welding zones are analyzed by simultaneously solving heat transfer and electromagnetic field equation. In particular, cone and flat type coils are designed and induction heating effects of each type are compared to identify heating characteristics on a V-groove weld joint. As a result, a cone shape coil is more efficient in the preheating process. When induction heating and arc welding system is designed for thick plate with V-groove weld joint, the results in this paper could be applied.
An Analytical Study on the Preheating Effect of Workpiece with Cylindrical Shape for 3-Dimensional Laser-Assisted Milling
Woo, Wan-Sick ; Lee, Choon-Man ;
Journal of the Korean Society for Precision Engineering, volume 32, issue 2, 2015, Pages 173~178
DOI : 10.7736/KSPE.2015.32.2.173
Laser-assisted machining (LAM) is an effective machining method for processing difficult-to-cut materials. Prediction and estimation of preheating effect of the LAM is difficult because of moving heat source. So it is necessary to study the preheating effect of the laser heat source irradiated on the curved surfaces of workpieces of various shape. In this paper, thermal analysis of the LAM for 3-dimentional workpiece with cylindrical shape was performed. The results of this analysis can be applied to obtain the optimal preheating method and path for LAM of 3-dimensional workpiece.
A Study on Shape Optimization of High-Speed Index Table with Hypoid Gear
Lee, Choon Man ; Ahn, Jong Wook ; Kim, Dong Hyeon ;
Journal of the Korean Society for Precision Engineering, volume 32, issue 2, 2015, Pages 179~184
DOI : 10.7736/KSPE.2015.32.2.179
In the recent field of Machining, with the improving efficiency of processing, the index table is a key unit according to the increase of parts in available processing when working with the three axes at the same time. As an essential product of MCT, the index tables effect an influence on product quality of machined parts. Therefore, it is necessary to design the shape of index table with stability, high stiffness, lightweight structure. In this study, the optimal shape of index table was proposed using by design of experiment. The maximum displacement and stress analysis were carried out by using FEM software. The optimized shape was verified by using the statistical software. The results of shape optimization were confirmed that both displacement and stress were reduced in comparison with initial model.
The Determination of Temperature and Humidity Sensitivity Coefficients of Torque Transducers using Seasonal Climatic Changes of Ambient Conditions in the Laboratory
Derebew, Mulugeta ; Kim, Min Seok ; Park, Yon Kyu ; Lee, Ho Young ;
Journal of the Korean Society for Precision Engineering, volume 32, issue 2, 2015, Pages 185~190
DOI : 10.7736/KSPE.2015.32.2.185
This paper presents a new method to determine sensitivity coefficients of temperature and humidity of torque transducers by using a natural and seasonal variation of ambient conditions at the laboratory. We had measured the sensitivities of the torque transducers over almost one year using the KRISS 2 kN m torque standard machine. The sensitivity data acquired at various ambient conditions were processed using our measurement model to extract the sensitivity coefficients of temperature and humidity simultaneously with high precision. A comparison with a previous method using an environmental control chamber was carried out to test the feasibility of using our new method. Two results agreed within the uncertainty. We revealed that the torque measuring errors could be 8 times higher than the measurement and calibration capability of KRISS torque standard machine if the sensitivity changes due to the temperature and humidity are not properly corrected during a calibration.
Six-degree-of-freedom Manipulator Displacement Measurement using Stereo Vision
Lee, Dong-Hyeok ; Baek, So Young ; Cho, Nahm Gyoo ;
Journal of the Korean Society for Precision Engineering, volume 32, issue 2, 2015, Pages 191~198
DOI : 10.7736/KSPE.2015.32.2.191
In this paper, six-degree-of-freedom (DoF). Displacement measurement technique using a compact stereo-vision system is proposed. The measuring system consists of a camera, an optical prism, two plane mirrors, and a planar marker on a target. The target was attached on an object so that its six-DoF displacement can be calculated using a proposed coordinates estimating algorithm and stereo images of the marker. A prototype was designed and fabricated for performance test. From the test results, it can be confirmed that the proposed measuring technique can be applied to monitoring and control of various manipulators.
Wearable Wellness Sensors and Devices (WWSD): State of the Arts and Challenges
Ahn, Bummo ;
Journal of the Korean Society for Precision Engineering, volume 32, issue 2, 2015, Pages 199~208
DOI : 10.7736/KSPE.2015.32.2.199
The aim of this paper is to review recent developments and commercialized products in the field of wearable wellness sensors and devices (WWSD). Although there are several dedicated researches, the completed theories and systematic techniques have not been well established. Therefore, we divided the WWSD into four different topics (healthcare, safety & prevention, gaming & lifestyle, and sports & fitness), and review the state of the arts and challenges on the applications on the sensor and device technologies with particular focus on WWSD. We also review the limitations of the current technologies on the developments and commercialized products. Finally, we suggest and discuss new research topics related on the four topics of the WWSD.
An Experimental Study on Mathematical Model to Predict Bead Width in GMA Weldment
Kim, Ill Soo ; Park, Min Ho ; Kim, Hak Hyoung ; Lee, Jong Pyo ; Park, Cheol Kyun ; Shim, Ji Yeon ;
Journal of the Korean Society for Precision Engineering, volume 32, issue 2, 2015, Pages 209~217
DOI : 10.7736/KSPE.2015.32.2.209
Generally welding is one of the most important processes to have a strong influence on the quality and productivity from a manufacture-based industry such as shipbuilding, automotive and machinery. The GMA(Gas Metal Arc) welding process involves large number of interdependent welding parameters which may affect product quality, productivity and cost effectiveness. To solve such problems, mathematical models are required to select the welding parameters for GMA welding process. In this study, the GMA welding process was studied using the information generated during the welding. The statistical analysis of a generalized regression approach was conducted by the following three methods: Firstly using the mathematical model (linear regression, 2nd regression); Secondly GA(Genetic Algorithm) with intelligent models; And finally using response surface analysis of models to develop the relationships between welding parameters and bead width as welding quality.
Optimal Design of a Plate-Fin Heat Sink with Slip Flow
Park, Boo Seong ; Park, Hyun Jin ; Kim, Bo Hung ;
Journal of the Korean Society for Precision Engineering, volume 32, issue 2, 2015, Pages 219~227
DOI : 10.7736/KSPE.2015.32.2.219
A dehumidifier using a thermoelement has many advantages compare to a dehumidifier using compressor systems. However, it is crucial to optimize the performance of heat sink for improving heat dissipation problem on the heat generation part. In this study, we utilized computational fluid dynamics software to compare Nusselt number, temperature and system efficiency based on fin thickness, flow gap between fin and fin length. Moreover, slip flow on the boundary layer was applied for the further analysis. Our objective in this study is to suggest an optimal fin shape to improve heat transfer with the tendency of performance factor depending on change of the shapes. Our results on the optimization of fin shape and analysis of slip flow will be utilized to enhance the heat transfer in the heat sink which is important in the design of dehumidifier using a thermoelement.