The role of dynamic behavior of operating rotor system in rotor design may or may not be evaluated under the impact of an external force such as earthquake. This article reports the result of an experimental study to resolve the dilemma. First, a sine weep test was performed to determine the first natural frequency of a Jeffcott rotor and compared with the ANSYS mode analysis demonstrating the reliability of experimental tests. The operating rotor vibrations were measured under the impact of sinusoidal forces at several frequencies, generated by the MTS vibration exciter. The experimental data suggest the need for a rotor design considering the dynamic behavior of the operating rotor under exciting external forces.

In this paper, it is proposed a method of optimizing path parameters for large-area laser processing. On-the-fly system is necessary for large-area laser processing of uniform quality. It is developed a MOTF(Marking On-The-Fly) board for synchronizing the stage and scanner. And it is introduced the change of the error due to the change of parameters and algorithm for large-area laser processing. This algorithm automatically generates stage path and a velocity profile using acceleration and deceleration parameters. Since this method doesn’t use a G-code, even if without expert knowledge, it has an advantage that can be accessed easily. Angle of one of the square of 350x350mm was changed from 50° to 80° and analyzed the error corresponding to the value of Ta. It is calculated the value of Ta of the best with a precision of 20um through measurement of accuracy according to the Ta of each angle near the edge.

Current electronic products are dominated by the laser processing and the application will be extended this time. Especially, demands for high precision laser processing with a large area has been increasing for a number of applications such as in solar cell battery, display parts, electronic component and automobile industry. In this paper we designed an on-the-fly system for ultrafast/high precision/large area laser processing. In addition, we have developed the path algorithm for large area. Expansion of the area in which laser processing is an important factor to handle the ultrafast/wide area processing, it will require a processing path. Processing path is path of 2- axis stage and stage of change in velocity can be smooth as possible. We proposed a path of the user concept using NURBS(Non-Uniform Rational B-Spline)method. Through our experiment with the chopper, was to prove the continuity of edge parts. Through basic shape experiments, we proved that large area can be processed using laser. We developed a simulation tool using Visual C++.

Recently, a study for the functional surface production of super hydrophobic of natural and biomimetic artificial has attracted much attention. To make process methods of super hydrophobic surface has a variety of ways such as lithography, etching, and laser ablation. However, we were used ultra-shot pulse laser ablation process which has the virtue of more environmental friendliness and simple process. In this paper, we were fabricated a multiplicity of super hydrophobic patterns on mold surface(NAK80) using by optimizing the laser processing conditions and it was transferred on PDMS. Also, we measured contact angle super hydrophobic patterns on PDMS. The result showed there is no patterns on PDMS were measured 94 degrees, by contrast, optimized super hydrophobic patterns on PDMS was 157 degrees. Therefore we fabricated super hydrophobic surface on mold. Based on these experimental results, it is possible to mass production using ultra shot pulse laser ablation of super hydrophobic pattern and to be applied for a variety of industries.

The LDS(Laser Direct Structuring) is one of the new direct writing methods to fabricate conductive patterns by energy beam. It uses thermoplastic polymers with an additive compound that serves as plating seed after the activation by laser. The advantages of LDS include the miniaturization of electrical components, design flexibility, and a reduced number of production steps. The purpose of this study is to investigate the fundamental mechanism for LDS and the characteristics of conductive patterns by laser parameters. These results were studied by SEM, EDX, and XPS analysis. We have used a 20W pulse-modulated fiber laser and copper electroless plating to fabricate conductive patterns on polymer. The result showed that electroless copper plating seed caused the laser cracking of additive compound. In particular, the additive compound contained in copper metal oxides atoms will be changed to copper metal elements. Also, the characteristics of conductive patterns were dependent on laser parameter, especially laser fluence.

We developed a path algorithm for ultrafast/wide area laser processing. Demands for high precision laser processing with a wide area has been increasing for a number of applications such as in solar cell battery, display parts, electronic component and automobile industry. Expansion of the area in which laser processing is an important factor to handle the ultrafast/wide area processing, it will require a processing path. Processing path is path of 2- axis stage and stage of change in velocity can be smooth as possible. In this paper, we proposed a smoothingnurbs method of improved speed profile. This method creates soft path from edge part, it is main purpose that scan area (50㎜ x 50㎜) inside processing path makes path of topology of possible straight line. We developed a simulation tool using Visual C++.

Due to the extremely short interaction time (＜ 10 × 10^-12sec) between laser pulse and material, which enables the minimization of heat affection, ultrafast laser micro-machining has rapidly widened its applications. In this paper, the characteristics of ultrafast laser micro-machining have been reviewed and experimentally demonstrated in laser drilling of silicon wafer and in laser cutting of rigid PCB.

In order to achieve and maintain dimensional accuracy in laser micro-machining, dominant parameters such as laser power and laser focus position need to be monitored and controlled real time. Also, in order to selectively machine multi-layered materials, the material being presently machined need to be recognized. This paper presents an auto-focusing (AF) module to keep laser focus on a large-area surface; a real-time laser power stabilizing module based on optical attenuation; and a laser-induced breakdown spectroscopy (LIBS) module. With these monitoring modules, position error in laser focus on a 4” silicon wafer was kept below 4㎛, initially 51㎛, and laser power stability of a UV laser source was improved from 1.6% to 0.3%. Also, the material transition from polyimide to copper in machining of FCCL (flexible copper clad laminate) was successfully observed.

In this paper, laser-assisted machining (LAM) has been employed to machine hot isostatically pressed (HIPed) Si3N4 workpieces. Due to little residual flaws and porosity, HIPed Si3N4 workpieces are more difficult to machine compared to normally sintered Si3N4 workpieces. In LAM, the intense energy of laser was used to enhance machinability by locally heating the workpiece and thus reducing yield strength. In experiments, the laser power ranges from 200W to 800W and the diameter of workpieces is 16mm. While machining, the surface temperature was kept nearly constant by laser heating except for a short period of rise time of max. 58 seconds. Results showed as feed rate increases the surface temperature of Si3N4 workpieces decreases slightly, whereas the effect of depth of cut is disregardable. With a laser power of 800W, achievable maximal depth of cut was 0.7㎜ and feed rate was 0.03㎜/rev.

Manufacturing process for the micro fluidic device can include such sequential steps as master fabrication, electroforming, and injection molding. The laser ablation using masks has been applied to the fabrication of channels in micro fluidic devices. In this study, manufacturing of polymer master and mold insert for micro injection molding was investigated. Ablation of PET (polyethylene terephthalate) by the excimer laser radiation could be used successfully to make three dimensional master for nickel mold insert. The mechanism for ablative decomposition of PET with KrF excimer laser (λ: 248 ㎚, pulse duration: 5 ㎱) was explained by photochemical process, while ablation mechanism of PMMA (polymethyl methacrylate) is dominated by photothermal process, the reaction between PC (polycarbonate) and KrF excimer laser beam generate too much surface debris. Thus, PET was adopted in polymer master for nickel mold insert. Nickel electro forming using laser ablated PET master was preferable for replication method. Finally, it was shown that excimer laser ablation can substitute for X-ray lithography of LIGA process in micro structuring.