• Design & Manufacturing
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• v.13 no.1
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• pp.5-12
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• 2019

In this paper, we studied the micro tool deflection, micro cutting with low temperature, and deformation of micro ribs caused by cutting forces. First, we performed an integrated machining error compensation method based on captured images of tool deflection shapes in micro cutting process. In micro cutting process, micro tool deflection generates very serious problems in contrast to macro tool deflection. To get the real images of micro tool deflection, it is possible to estimate tool deflection in cutting conditions modeled and to compensate for machining errors using an iterative algorithm correcting tool path. Second, in macro cutting fields, the cryogenic cutting process has been applied to cut the refractory metal but, the serious problem may be generated in micro cutting fields by the cryogenic environment. However, if the proper low temperature is applied to micro cutting area, the cooling effect of cutting heat is expected. Such effect can make the reduction of tool wear and burr formation. For verifying this passibility, the micro cutting experiment at low temperature was performed and SEM images were analyzed. Third, the micro pattern was deformed by the cutting forces and the shape error occurred in the sidewall multi-step cutting process were minimized. As the results, the relationship between the cutting conditions and the deformation of micro-structure during micro cutting process was investigated.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.E2
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• pp.78-88
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• 2006

In order to study the characteristics of cloud, a real-scale experiment for cloud generation was carried out using an extinct vertical mine (430 m height) located in the northeastern Honshu, Japan. The dry particles generated from the three-step concentrations of NaCl solutions were used for cloud generation. The number size distributions of initial dry particles and cloud droplets were monitored by Scanning Mobility Particle Sizer (SMPS) and Forward Scattering Spectrometer Probe (FSSP) at bottom and upper sites of pit, respectively. The polymeric water absorbent film (PWAF) method was employed to measure liquid water content ($W_L$) as a function of droplet size. Moreover the chemical properties of individual droplet replicas were determined by micro-PIXE. The CCN number concentration shows the lognormal form in dependence of the particle size, while the number size distributions of droplets are bimodal showing the peaks around $9{\mu}m$ and $20{\mu}m$ for every case. In comparison to background mineral particles, right shifting of size distribution line for NaCl particles was occurred. When NaCl solutions with three-step different concentrations were neulized, $W_L$ shows the strong droplet size dependence. It varied from $10.0mg\;m^{-3}$ up to $13.6mg\;m^{-3}$ with average $11.6mg\;m^{-3}$. A good relationship between $W_L$ and cloud droplet number concentration was obtained. Both chemical inhomogeneities (mixed components with mineral and C1) and homogeneities (only mineral components or C1) in individual droplet replicas were obviously observed from micro-PIXE elemental images.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.4
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• pp.526-534
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• 2016

A MEMS solid propellant thruster array shall be operated within an allowable range of operating temperatures to avoid ignition failure by incomplete combustion due to a time delay in ignition. The structural safety of the MEMS thruster array under severe on-orbit thermal conditions can also be guaranteed by a suitable thermal control. In this study, we propose a thermal control strategy to perform on-orbit verification of a MEMS thruster module, which is expected to be the primary payload of the STEP Cube Lab mission. The strategy involves, the use of micro-igniters as heaters and temperature sensors for active thermal control because an additional heater cannot be implemented in the current design. In addition, we made efforts to reduce the launch loads transmitted to the MEMS thruster module at the system level structural design. The effectiveness of the proposed thermo-mechanical design strategy has been demonstrated by numerical analysis.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.5
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• pp.637-645
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• 2009

The main purpose of this study lies on the improvement of micro dilution tunnel based on the typical porous tube type chamber. The characteristics of flow and temperature fields for steady state has been obtained by numerical analysis using FLUENT. Three different geometrical variations of the porous tube; a) increase of thickness at center, b) step increase of thickness at center and downstream, c) tapered increase of thickness, have been proposed. Accordingly results are obtained and compared in terms of penetration velocity and velocity ratio to therrmophoretic velocity for improvement against particulate deposition inside the tube. The penetration velocity and velocity ratio distributions in the upstream portion and portion of impinging of dilution air are apparently shown to be improved for the case of the step and tapered change of porous tube. The tapered change of tube thickness addition are shown to be the most effective among three geometrical changes. In addition, the considerable improvement against deposition are shown that its thickness should be at least 2mm.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.3
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• pp.370-375
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• 2010

Tungsten carbide microshaft is used as micro punch, electrode of micro electro discharge machining, and micro tool because of its high hardness and rigidity. In this research, tungsten carbide microshaft was fabricated using electrochemical machining. $H_2SO_4$ solution was used as the electrolyte because it can dissolve tungsten carbide and cobalt simultaneously. Experimentally studied were the effects of electrolyte concentration, machining time, and machining voltage on material removal rate and the shape of the microshaft. To eliminate the effects of bubbles and metal corrosion layer on microshaft shape, the machining was performed below the electrolysis voltage. Three step electrochemical process was suggested to fabricate the straight tungsten carbide microshaft. As a result, a straight tungsten carbide microshaft of $30{\mu}m$ in diameter and $500{\mu}m$ in length was obtained through the proposed three step electrochemical process.

• Journal of the Optical Society of Korea
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• v.18 no.1
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• pp.37-44
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• 2014

The use of a laser interferometer as a metrological tool in micro-optics measurement is demonstrated. A transmissive interferometer is effective in measuring an optical specimen having a high angle slope. A configuration that consists of an optical resolution of 0.62 micron is adapted to measure a specimen, which is a micro-Fresnel lens-shaped lenticular lens. The measurement result shows a good repeatability at each fraction of facets, however, a reconstruction of the lens shape profile is disturbed by a known problem of $2{\pi}$-ambiguity. To solve this $2{\pi}$-ambiguity problem, we propose a two-step phase unwrapping method. In the first step, an unwrapped phase map is obtained by using a conventional unwrapping method. Then, a proposed unwrapping method based on the shape modeling is applied to correct the wrongly unwrapped phase. A measured height of each facet is compared with a profile result measured by AFM.

• Journal of Korean Society for Quality Management
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• v.51 no.3
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• pp.461-479
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• 2023

Purpose: It emphasizes the importance of cost analysis for weapons systems that require enormous develop- ment costs, analyzes the problems of cost analysis steps from a practical point of view, and presents the direction of business development in terms of cost analysis reliability, timeliness, and efficiency. Methods: It analyzes the R&D cost of Micro satellites with a complex cost structure and large scale according to engineering estimation procedures, derives major analysis step-by-step problems, and presents business development directions. Results: Problems with standards and assumptions, data collection, cost division structure, and cost estimation methods were derived through the micro satellite cost analysis process, and business development directions such as expanding common standards, standardizing basic data, standardizing cost division structures and cost items, and data asset were presented. Conclusion: In order to develop work in terms of cost analysis reliability, timeliness, and efficiency, it is important to prepare and standardize standards and rules for detailed tasks at each analysis stage, and through this, it is expected that high utilization value and systematic cost data will be assetized in the future.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.175-178
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• 2000

An aerostatic stage has frictionless behavior, so it has a advantage of investigation into positioning characteristics. A one-dimensional aemstatic ceramic stage with ballscrew driven and laser scale feedback system is manufactured. aiming at investigating positioning characteristic of aerostatic stage, especially position error and repeatability, we analyze positioning behavior with other factors such as angular error, temperature. Experimemal results show that the aerostatic stage has a l0nm micro step response. Comparing experimental results and calculated abbe's error, we confirm that mean of position error is owing to angular error. And, also we confirm the temperature is dominant factor of repeatability in ten nm order.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.610-614
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• 1996

As the run out error and misalignment of ball screw connected directly to guide table largely affect the motion accuracy of guideway, floating coupling that releases the table from screw nut except feed and rotational direction is needed todecrease its influences. The purpose of this study is to propose a practical model floating coupling of ball serew for high precision feeding system. The straightness, dynanic characteristics and micro step response of hydrostatic guideway, mounted with three types of coupling fixed type, leaf spring type and hydrostatic type, are tested and compared. From the resuts of experiments, it is proved that a hydrostatic type floating coupling is superior to other couplings and is available to high precision feeding system with ball screw.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.668-671
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• 2000

An aerostatic stage has frictionless behavior, so it has a advantage of investigation into driven mechanism such as ballscrew. In this paper, fur investigating positioning characteristic of ballscrew and feedback device in aerostatic stage, we compare the positioning characteristic between full-closed(laser scale) and semi-closed(encoder) system. Experimental results show that the aerostatic stage has a 10nm micro step response and repeatability is improved up to 1.00${\mu}{\textrm}{m}$ using laser scale. We confirm the laser scale compensate error motion of ballscrew, so acquire 1.12${\mu}{\textrm}{m}$ positioning accuracy.