• Laser Solutions
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• v.13 no.4
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• pp.7-13
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• 2010

Today, the most common process for generating Through Silicon Vias (TSVs) for 3D ICs is Deep Reactive Ion Etching (DRIE), which allows for high aspect ratio blind holes with low surface roughness. However, the DRIE process requires a vacuum environment and the use of expensive masks. The advantage of using lasers for TSV drilling is the higher flexibility they allow during manufacturing, because neither vacuum nor lithography or masks arc required and because lasers can be applied even to metal and to dielectric layers other than silicon. However, conventional nanosecond lasers have the disadvantage of causing heat affection around the target area. By contrast, the use of a picosecond laser enables the precise generation of TSVs with less heat affected zone. In this study, we conducted a comparison of thermalization effects around laser-drilled holes when using a picosecond laser set for a high pulse energy range and a low pulse energy range. Notably, the low pulse energy picosecond laser process reduced the experimentally recast layer, surface debris and melts around the hole better than the high pulse energy process.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.3
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• pp.73-79
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• 2012

This paper describes the machining characteristics of the sintered carbide and die steel(STD-11) by electric discharge drilling with various tubular electrodes. Electrical discharge machining(EDM) removes material from the workpiece by a series of electrical sparks that cause localized temperatures high enough to melt or vapourize the vicinity of the charge. In the experiment. four types of electrode which have different diameter are used with the application of continuous direct current and axial electrode feed. The controlled factors include the dimension of the electrode. In drilling by EDM, the dielectric flushed down the interior of the rotating tube electrode, in order to order to facilitate the removal of machining debris the hole. The expansion increase with increasing the thickness of material and the diameter of electrode and the expansion of sintered carbide is 1.75 times large then that of die steel. The taper of machined hole decrease with increasing the thickness of material. The crater sixe of die steel is larger then thet of sintered carbide and the surface roughness of sintered carbide is 1.58 tims larger then that of die steel.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.1021-1024
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• 2001

Out of all metal-cutting processes, the hole-making process is the most widely used. It is estimated to be more than 30% of the total metal-cutting process. It is therefore desirable to monitor and detect drill wear during the hole-drilling process. In this paper, the vision system of the sensing methods of drill flank wear on the basis of image processing is used to detect the wear pattern by non-contact and direct method and get the reliable wear information about drill. In image processing of acquired image, median filter is applied for noise removal. The vision flank wear area of the drill was measured. Backpropagation neural networks (BPns) were used for no-line detection of drill wear. The neural network consisted of three layers: input, hidden and output. The input vectors comprised of spindle rotational speed, feed rates, vision flank wear, thrust and torque signals. The output was the drill wear state which was either usable or failure. Drilling experiments with various spindle rotational speed and feed rates were carried out. The learning process was peformed effectively by utilizing backpropagation. The detection of the abnormal states using BPNs achieved 96.4% reliability even when the spindle rotational speed and feedrate were changed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.7 no.3
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• pp.30-35
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• 2008

As demands for being economical, precise drilling process is on the increase. Therefore, the objective of this study is to develop a step cutter that can be controllable through micro dimension and can be changed from separate manufacturing processes of drilling and boring into an integrated one. In order to attain this object the step cutter is designed with a 3D geometric modeling and the design could be modified easily by using parametric modeling methodology. Also, collision is not occurred during manufacturing process because of cutting simulation. The step cutter is assembled by parts made up of 5-axis machining and sintering. Validation tests are accomplished. They show that developed cutter has characteristics such as reduction of machining time as well as the good surface roughness of the machined hole. Indeed, reliability could be obtained from a durability test.

• Korean Journal of Computational Design and Engineering
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• v.18 no.4
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• pp.243-249
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• 2013

This paper presents a tool-path generation methods for an automated robotic system for skull drilling, which is performed to access to some neurosurgical interventions. The path controls of the robotic system are classified as move, probe, cut, and poke motions. The four motions are the basic motion elements of the tool-paths to make a hole on a skull. Probing, rough cutting and fine cutting paths are generated for skull drilling. For the rough cutting path circular paths are projected on the offset surfaces of the outer top and the inner bottom surfaces of the skull. The projected paths become the paths on the top and bottom layers of the rough cutting paths. The two projected paths are blended for the paths on the other layers. Syntax of the motion commands for a file format is also suggested for the tool-paths. Implementation and simulation results show that the possibility of the proposed methods.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.7
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• pp.7-14
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• 1999

어브레시브 워터젯을 이용한 Drilling시 깊이에 대한 예측은 가장 중요한 변주중의 하나다. 이 논문에서는 구멍 깊이의 예측 및 구멍 형상을 연구하기 위하여 3차원 해석 모델이 제안되었다. 해석 모델은 크게 두 가지로 구성되었다. 하나는 비선형 반복 방정식에서 생성된 입자의 운동식이며, 다른 하나는 수많은 입자에 의한 충돌시 가공능력을 규정지우는 Constitutive Equation으로 구성되었다. 이 모델은 구멍 가공이 진행됨에 따라 발생하는 감쇠 효과를 고려하였다.실험적인 고찰이 해석모델의 유용성을 검증하기 위하여 이루어졌으며, 근사한 결과를 보였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.1052-1055
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• 2001

In micro-drilling of brittle materials including glass, cracks occur at the exit surface. In drilling glass, the main type of crack is cone crack. Cone crack is generated by thrust force acting at the bottom surface of the workpiece. Cone crack size could be reduced by changing cutting conditions, but cone crack still existed. Two methods were proposed to prevent crack formation and perfect hole shapes were obtained. One method is attaching two glass plates with water and the other method is constraining two glass plates. The proposed methods eliminated tensile stress acting on the exit surface of glass and prevented crack propagation.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.240-245
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• 2000

This paper presents the experimental study of drilling for duralumin A2024 with intermittently decelerated feed rate. It is achieved through a programmed periodic increase and decrease in the feed rate using a machining center. The following experimental result were performed with the objective of solving chip to disposal problems. In conventional drilling of aluminum, long continuous chips are produced that wind around the drill causing difficulties in eliminating chips from the cutting zone. In order to acquire the basic data necessary to regulate the chip profile, the relationship between cutting variables and chip shape was investigated. The following conclusions are established from the experimental results. At a suitable feed fluctuation ratio, intermittently decelerated feed drilling proved successful in breaking chips to appropriate lengths while maintaining stable cutting. Thus, it is an effective method for improving chip disposal. The amplitude of the dynamic component of cutting force in intermittent feed frilling is influenced by the feed fluctuation ratio.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.331-332
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• 2002

Most manufacturing processes such as welding, cutting and molding generate residual stresses on the surface of manufactured parts. Tensile residual stress is harmful to the surface integrity, which results in reduced fatigue life and causes other structural failures when the service stresses are superimposed on the residual stresses. In the research, the residual stresses of the high hardness steel (over $H_{RC}60$) workpiece (SKD11) machined by the hard turning were measured using Hole-drilling Method. Residual stress in the surface of hard turned workpiece was mainly appeared to be compressive stress.

• Journal of the Korean Society of Safety
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• v.23 no.3
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• pp.8-11
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• 2008

In the present work, the measurement method of residual stresses in thermal barrier coatings(TBCs) which are received the thermal shock is performed numerically. For this, the internal residual stresses are predicted by commercial FEM software ABAQUS because the hole drilling strain gage method measures residual stresses only near the surface of a material. As the results of this study, the residual stresses are linearly increased when the surface temperatures are over $1,200^{\circ}C$. It is also found that the values of residual stress are increased as the coating thickness is thin.