• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.930-933
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• 2000

Experimental study was conducted for finding the characteristics of machining precision according to the change of feedrate when ball endmilling of semisphere shape. The values of tool deflection and cutting force were measured simultaneously by the systems of eddy-current sensor and dynamometer. The machining precision was analyzed by roundness values, which were deeply relating with tool deflection and forces. the roundness was decreased in down-milling than in up-milling for each feedrate. As the cutting edge is moved to radius direction on the tool path, the tool deflection and the cutting force were seemed to be decreased. As the tool path was moved downward, the values of roundness, cutting force and tool deflection were obtained better ones. When compared the values of roundness, cutting force and tool deflection for different feedrate, the best machining accuracy was obtained at feed rate of 90mm/min in down-milling.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.227-232
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• 2002

This paper presents an algorithm for general 2D and 3D NURBS interpolation and deals with command generation for 3 axes milling machining, including the feedrate control in order to meet two limitations, a geometrical accuracy and a dynamic restriction. Both of the maximum chordal error and the maximum acceleration specified by machine parameter lead to limit the allowable feedrate on the curvature of NURBS tool path. So, motion commands at every sampling time are continuously generated by those two limitations and programmed feedrate. Simulation results of interpolating several NURBS curves show that proposed NURBS algorithm is favorable in the machining free-form curve

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.6
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• pp.1456-1464
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• 1993

The achievable machining accuracy depends upon the level of the micro-engineering, and the dimensional tolerances in the order of 10 nm and surface roughness in the order of 1 nm are the accuracy targets to achieved today. Such requirements cannot be satisfied by the conventional machining processes. Single point diamond turning is one of the new techniques which can produce the parts with such accuracy limits. The aims of this thesis are to get a better understanding of the complex cutting forces. A cutting model for describing the influence of cutting conditions (cutting speed, feedrate and depth of cut), material properties of the workpiece and tool geometry has been proposed after estimating the two cutting force models-the Recht model and the Dautzenberg model. The experiments with Al-alloy workpieces, which have been carried out in order to estimate the models, show that the proposed model in this thesis is better than the two models. As the depth of cut and feedrate are increased in the operations settings (depth of cut 8-100$\mu{m}$, feedrate 8-140$\mu{m}$/rev, and cutting speed 8 m/sec), the relation of dimensionless cutting forces from experiments are similar to the proposed model. With the undeformed chip area of $30-80{\times}10^{2}$\mu{m}^2$, the experimental cutting forces accord with the force prediction.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.51-54
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• 2002

This paper deals with an implementation of NUBS interpolator and presents the process of its integration into PC-NC. For more accurate feed, NURBS algorithm is improved. Also, Evaluation of real time NURBS interpolator is provided to verify fred accuracy and geometrical accuracy of NURBS curve. NURBS machining of fee surface is simulated on the real time NC simulator so that machining time is compared to that of linear path machining.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.1 no.1
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• pp.5-14
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• 2002

Hemisphere shapes were machined for different tool paths and machining conditions with ball endmill cutters. It was also found out how feedrate affect the precision of the machining and also tried to study the most suitable feedrate in specific cutting condition. Tool deflection, cutting forces and shape accuracy were measured according to the inclination position of the sculptured surface. As the decreasing of inclination position angle, the tool deflection was increased due to the decreased cutting speed when the cutting edge is approaching toward the center. Tool deflection when upward cutting IS obtained less than that of downward cutting and down-milling in upward cutting showed the least tool deflection for the sculptured surface. For down-milling, the cutting resistance of the side wall direction is larger than that of feed direction. It was found that the tool deflection is getting better as tool path is going to far from the center for convex surface.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.2
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• pp.1-8
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• 2003

Conventionally used linear or circular interpolator is undesirable for the precision machining of 3D free-form surface as the following reason: the transmission errors due to the huge number of data, discontinuity of segmentation, unsmooth motion speed. To this regard, modern CNC machine tools are designed with the function of machining arbitrary parametric curves. However, these systems don't consider the adaptive federate, which dominates the quality of the machining process. This paper proposes a NURBS interpolator for the constant material removal rate. That is accomplished by the variable federate using curvature of curve. The curvature-compensated feederate system has important Potential applications in ensuring part accuracy and protecting cutting tool. The simulated result show it can be applicable to the real machining.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.2
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• pp.58-64
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• 2002

In these days, according to increasing the technical development, the dimension of a product goes up for ultra-precision. For the net shape manufacturing, grinding is a important process that influences directly the accuracy and the integrity of produced products. In this study, an experimental evaluation was carried out. Workpiece materials were used STD11, SUS304, and STB2 in accordance with varing condition of feedrate and depth of cut. From measuring the grinding force and the surface roughness, material characteristics of grinding by using CBN wheel were examined.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.471-474
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• 2004

In this paper, a NURBS surface interpolator is proposed which can deal with shapes defined from CAD/CAM programs on a surface basis and can improve contour accuracy. The proposed interpolator is based on newly defined G-codes and includes online tool-path planning suitable for NURBS surface machining. The real-time interpolation algorithm, considering an effective machining method for each machining process and minimum machining time, is executed in an online manner. The proposed interpolator is implemented on a PC-based 3-axis CNC milling system and evaluated through actual machining in terms of machining time and regulation of feedrate and cutting force in comparison with the existing method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.11
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• pp.1053-1058
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• 2007

Micro-EDM technology (or the manufacture of miniature parts is used to make a micro hole. Two electrode shaping methods, mechanical electrode grinding and WEDG technique, have been studied. In this study, an electrode shaping method by using previously machined hole is introduced in order to obtain an optimal hole-making condition. Key factors such as applied voltage, capacitance, feedrate, and hole-dimension have an influence on the fabricating error of electrode shaping, which are taper ratio of a hole, electrode form accuracy, and electrode surface. Therefore, we try to investigate the optimal fabricating of electrode shaping from various experiments. Results from experiments, it was able to minimize the electrode fabricating error as voltage increases, and also applied feedrate and capacitance decreases.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.1105-1108
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• 2001

In these days, according s the increase of technological development the part demension goes up for ultra-precision. It is grinding behavior that is important processing which directly influences by machining accuracy at product quality with the net shape manufacturing. In this study, by using CBN wheel an analysis carried out for workpiece's profiles and its characteristics by measuring grinding force and surface roughness. Workpiece materials were used STD11, SUS304 and STB2 varing condition of feedrate and depth of cut.