• Journal of the Korean Society for Precision Engineering
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• v.19 no.11
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• pp.183-191
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• 2002

Drilling tests were carried out using drills with various drill shapes for burr minimization. Final objective of this study is to develop compatible drill shape for minimization of burr formation. For experiments, general carbide drills, round drills, chamfered drills and step drills are designed and manufactured. Burrs are formed by various cutting conditions and in 4 different work materials. Laser sensor is used to measure burr geometries. Cutting forces in drilling are also measured and compared in every drill. As a result of the experiments, step drills with specific step angle and step diameter are suggested for burr minimization.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1991.11a
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• pp.54-58
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• 1991

It is well known that metal cutting leaves a plastically deformed layer in the machined surface. This residual phenomenon affects in various forms the physical properties of machined components such as the fatigue strength, the dimensional instability, microcracks, and the stress corrosion cracking. These physical properties, so called surface integrity, are very important for designing highly stressed and critically loaded components. Typical plastic strains in the machined surface are very difficult to measure, since they are located within a very short distance from the surface and they change very rapidly. There is an alternative way to determine the residual strain in plastically deformed materials by measuring the grain size after a subsequent recrystallization process. Although, this technique has been successfully applied by several researchers to find the plastic zone around notches and cracks in various materials and welding beads, few works have been reported using the recrystallization method to determine the residual strains in machined surface. Therefore, the purpose of this investigation Is to explore the effectiveness of the recrystallization technique in machining applications, and in particular, to find the effect of cutting parameters, i.e., depth of cut and rake angle on the plastic strains.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.10a
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• pp.85-90
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• 2001

Recent general Press brake has many problems in cutting high accurate products in the progress of industry. Previous hand-operated press brake needs many pre-processing works to adjust bending ang1e and marking-off works to calculate bending length. Also, the hand-operating work makes many geometric errors and has difficulty for variety-mass production. To solve these problems, this paper proposes Computer Numerical Control (CNC) general press brake and development of servo-control system based on database for reduction of geometric errors and pre-processing work time and high accuracy bending work.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.363-366
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• 2001

Many joint parts by welding are found in the compression vessels, ship structures, pipings, heat exchangers, etc. Before their welding, steel plate cutting in a required form is very important. But because of the present CAD system's capability, unless otherwise expensive general CAD system is equipped, the efficiency or the accuracy of the cutting work can not be achieved easily. In order to get over this sort of problems, application-specific software that is limited on for the development view of the joint parts in those sort of facilities mentioned before was developed in this study.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.4
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• pp.141-147
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• 1998

A plastically deformed layer in the precision machined surface affects in various forms the physical properties of machined components such as the fatigue strength, the dimensional instability, microcracks and the stress corrosion cracking. These physical properties, so called surface integrity, are very important for designing highly stressed and critically loaded components. Typical plastic strains in the precision machined surface are very difficult to measure, since they are located within a very short distance from the surface and they change very rapidly. A new way is suggested to determine the residual strain in plastically deformed materials by analyzing the plastically deformed layer after a subsequent recrystallization process. This investigation is to explore a new technique for measuring plastic strain in machining applications, and in particular, to and the effect of cutting parameters(rake angle, depth of cut, specific cutting energy), on the plastic strains and strain energy.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.513-518
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• 1999

In this study, geometrical similarity conditions for drills of various diameters are discussed. The effect of geometrical similarity on the chip shape and forces of different sized conventional drills has been experimentally confirmed. Drilling tests are carried out for SM45C by using the conventional HSS drills. The torque and thrust forces are measured and compared with those chip forms. Chip shape in drilling are affected by three factors being flow angle, side and up curl of the chip. It is found that the feedrate and drill diameter are more affected than cutting speed on the chip form and cutting forces. The similarity conditions gives easily to estimate the chip shape, the thrust and the torque for drills of different diameters.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.591-596
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• 1999

Due to the development of CNC machining centers and the complexity of machined part geometry, the ball-end milling became the most widely used the cutting process. Generally, the tool runout defined as the eccentricity of a rotating tool set in the holder involved the spindle runout and the problem of tool runout generated to remove the workpiece is a main factor affecting the machining accuracy. In this paper, the relationship of tool runout(zero-to-peak, P-K) and surface shape on the change of cutting conditions is studied and it is proposed the probability of prediction of surface shape from the in-process tool runout measurements with high response displacement sensor in the ball-end milling

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.6
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• pp.793-798
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• 2011

In this study, it was grasped to the flow characteristics of cutting fluid injected by nozzle installed in high pressure holder for avoiding chip curling occurred during machining process. And for avoiding chip curling, the possibility of elimination under various chip conditions was checked. Consequently, the highest discharging pressure and velocity was shown in 150 of nozzle inflow angle. Also as nozzle outlet diameter is small, the pressure and velocity of injected flow are high. Moreover, It could be confirmed that width and thickness of chip have no direct effect on chip elimination and it is achieved by torque generated by injected cutting fluid.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.8
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• pp.1309-1316
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• 2003

The general dicing process cuts a semiconductor wafer to lengthwise and crosswise direction by using a rotating circular diamond blade. But products with inferior quality are produced under the influence of several parameters in dicing process such as blade, wafer, cutting water and cutting conditions. Moreover we can not apply this dicing method to GaN wafer, because the GaN wafer is harder than the other wafer such as SiO2, GaAs, GaAsP, and AlGaAs. In order to overcome this problem, development of a new dicing process and determination of dicing parameters are necessary. This paper describes a new wafer dicing method using fixed diamond scriber and precision servo mechanism and determination of several parameters - scribing depth, scribing force, scriber inclined angle, scribing speed, and factor for scriber replacement - for a new dicing machine using scriber.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.9-14
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• 1996

The deflection of an end mill is very important in machining process and cutting simulation because it affects directly workpiece accuracy, cutting force, and chattering. In this study, the deflection of the end mill was studied both experimentally and by using finite element analysis. And the moment of inertia of radial cross sections of tile helical end mill is calculated for the determination of the relation between cross section and rigidity of tile tools. Using tile Bernoulli-Euler beam and and the concept of equivalent diameter, a deflection model is established, which includes most influence from tool geomety parameters. It was found that helix angle attenuates the rigidity of the end mill.