저주파 가진 시스템에 의해 성형된 마이크로 패턴의 특성 분석

박찬진(C. J. Park),최종필(J. P. Choi),박동영(D. Y. Park),홍남표(N. P. Hong),이혜진(H. J. Lee),이낙규(N. K. Lee),김성욱(S. O. Kim),주은덕(Andy Chu),김병희(B. H. Kim) 한국생산제조학회 2009 한국공작기계학회 추계학술대회논문집 Vol.2009 No.-

Many researchers have developed several micro-forming technologies such as micro deep drawnig, micro press forming, micro forging, extrusion etc. for forming of precise micro-patterns on a surface of metal substrate but the multi-step forming processes have been used to improve quality of the deformed patterns. The low frequency vibration forming system, which developed in the research, can not only easily deform the surface of metal substrates but also can remove the couple of steps of the conventional multi-step forming process. In order to find optimal process conditions, lots of experiments were carried out under varying the vibration frequency from 100㎐ to 500㎐. As a experimental results, The desktop micro forming system has obtained better results from low frequency vibrations than non-vibration.

A study on the micro-formability of Al 5083 superplastic alloy using micro-forging method

Kang, S.G.,Na, Y.S.,Park, K.Y.,Jeon, J.E.,Son, S.C.,Lee, J.H. Elsevier 2007 Materials science & engineering. properties, micro Vol.449 No.-

<P><B>Abstract</B></P><P>Micro-formability of superplastic Al 5083 alloy as a candidate material for micro-forming was investigated by varying the forming parameters such as time, load and temperature. Micro-forging machine and Si micro-dies with V-groove were employed for micro-forming test. Micro-formability was estimated by comparing <I>R</I><SUB>f</SUB> values (=<I>A</I><SUB>f</SUB>/<I>A</I><SUB>g</SUB>), where <I>A</I><SUB>g</SUB> is cross-sectional area of V-groove, and <I>A</I><SUB>f</SUB> the filled area by micro-formed sample. The <I>R</I><SUB>f</SUB> values increased with increasing load and time when the forming temperatures were in the range where superplasticity of Al 5083 alloy is manifest. On the other hand, the <I>R</I><SUB>f</SUB> values decreased as the forming temperatures got away from the superplastic temperature of Al 5083 alloy. Maximum <I>R</I><SUB>f</SUB> value (0.9952) was reached at temperature 530°C, load 96N and time 20min.</P>

Evaluation on Ground Surface Accuracies of Large-Depth and Steeply Micro-Structured SiC Surfaces

Ping Li,Xiaochu Liu,Junwu Chen 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.2

Microstructures can be used to enhance technical surfaces with additional functionalities, which are driving advances in many fields of industrial applications. However, it is difficult to obtain 3D valid information about large-depth and steeply micro-structured surfaces owing to the limitation of the white light interferometric measurements. Therefore, the registration of bisection-measured micro-topographies is proposed using the interactive closest point (ICP) method combined with the genetic algorithm, with the objective of evaluating the micro-form and micro-profile accuracies of a micro-structured surface. First, a diamond grinding-wheel V-tip was employed to fabricate micro-pyramid-structured SiC; subsequently, 3 ideal point models were constructed to match the measured point clouds using the ICP method; finally, the non-dominated sorting genetic algorithm-II (NSGA-II) was used to micro-alignment the bisection-measured point clouds with regard to micro-form and micro-profile errors. It is shown that the registration accuracy is dominated by the ideal profile point number, but the registration efficiency depends on the ideal point number. The the NSGA-II could improve the registration accuracy of micro-profile by 42.6% compared with traditional ICP matching. It is confirmed that the micro-grinding is able to control the micro-form and the micro-profile accuracies within 4%.

마이크로 기어 제조용 압출장치 개발

이경훈(K.H. Lee),고대철(D.C. Go),김상주(S.J. Kim),김병민(B.M. Kim) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11

This paper presents a study on micro forming technologies for micro-electro-mechanical systems(MEMS) parts such as micro gears below 450㎛ in diameter and 38 in module. For this purpose, it is important to develop new methods to fabricate micro gears and choose suitable materials for micro forming. Generally micro gears made by MEMS process butin this study micro gears made by extrusion process using micro dies. Photochemically machinable glass has been used to fabricate micro dies by photo-lithography and anisotropic etching techniques. A new forward extrusion machine has been developed for this study. LLDPE(Linear Low Density Polyethylene) and EVA(Ethylene Vinyl Acetate) have been used in micro extrusion. Specimens were placed in a container and extruded by a piezoelectric actuator. Micro extrusion has succeeded in forming micro-gear shafts.

Two-stage forming approach for manufacturing ferritic stainless steel bipolar plates in PEM fuel cell: Experiments and numerical simulations

Bong, Hyuk Jong,Lee, Jinwoo,Kim, Jong-Hee,Barlat, Fré,dé,ric,Lee, Myoung-Gyu Pergamon Press 2017 International journal of hydrogen energy Vol.42 No.10

<P><B>Abstract</B></P> <P>Multi-stage micro-channel forming by stamping, as a method for cost effective and efficient for mass production, was performed for ultra-thin ferritic stainless steel sheets with thicknesses of 0.1 and 0.075 mm, as a good substitute for traditional graphite bipolar plates of proton exchange membrane fuel cell. Attention was directed to enhance the final forming depth and minimize localized thinning, extremely important aspects of the micro-channel on bipolar plate, by the proposed forming process. A forming depth at the first forming stage was chosen as a process variable, and its effect on the formability of the micro-channel at the second forming stage was experimentally investigated. Finite element simulations for the two-stage forming process were conducted to optimize the punch radius and forming depth at the first stage for improving the formability. The comparative study between the simulations and the experimental results could validate improvements in the formability by the proposed approach. In particular, this study could support the existence of an optimum forming depth at the first forming stage. Based on the simulation results, a mathematical model was established to identify the dominant factor needed for formability improvement and to propose a methodology for the process optimization of the multi-stage forming.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Formability of ultra-thin sheet is improved by two-stage forming. </LI> <LI> Finite element simulation is agreed well with the experiments. </LI> <LI> A simple phenomenological model is proposed for optimization of two-stage forming. </LI> </UL> </P>

Investigation of processing parameters in micro-thermoforming of micro-structured polystyrene film

Trieu Khoa Nguyen,이봉기 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.12

In this study, a thermoforming process for manufacturing micro-structured polystyrene (PS) films is investigated to characterize the effects of significant processing parameters. The present micro-thermoforming process utilizes a mold core with five concave rectangular grooves (each of width 0.4–1.2 mm and a depth of 1 mm). Two types of PS films (thicknesses of 50 and 190 μm) are employed to examine the effect of film thickness. Three main processing parameters namely heating temperature, heating time, and mold core temperature are analyzed. The results show that as the width of the groove in the mold core decreases, the forming ratio (depth-to-width ratio of the thermoformed micro-feature) slightly reduces, consequently indicating poor thermoforming. Both thin and thick PS films exhibit similar forming results under favorable conditions. However, when the processing conditions are not suitably applied, the thick film shows the worst result. From the design of experiment analysis using a normalized forming ratio, the mold core temperature is found to be the most influential factor in the thermoforming process of manufacturing micro-structured PS films.

Micro-Forming Characteristics of a Zr-Based Amorphous Alloy with a Gear-Like Mold

( Kyu Yeol Park ),( Young Sang Na ),( Seon Cheon Son ),( Jong Hoon Lee ),( Van Bon Nguyen ) 대한금속재료학회 ( 구 대한금속학회 ) 2007 METALS AND MATERIALS International Vol.13 No.5

The amorphous alloy Zr62Cu17Ni13Al8 exhibits a supercooled liquid state over a wide temperature range under high temperatures. In this present paper, the authors studied the micro-forming ability of the alloy by compressing specimens under a miniature pattern mold with a micro-gear shape. Micro-compressive formation is a formation method in which the surface of specimens of the Zr62Cu17Ni13Al8 amorphous alloy is compressed under conditions of dead loads and high temperatures and maintained for a given period for the fabrication of miniature patterns with a micro-gear shape. All the experiments were carried out under a vacuum environment to prevent the specimens from suffering deleterious effects, such as air traps in the miniature patterns and oxidation at the surface of the Zr62Cu17Ni13Al8 amorphous alloy. The characteristics of micro-compressive formation were investigated at temperatures higher than the glass transition temperature with different experimental parameters of loads and times. In addition, the micro-forming characteristics of the gear-like shape were investigated by means of scanning electron microscopes and a 3-D surface profiler system.

Zr 계 벌크비정질합금의 마이크로 단조를 이용한 미세 성형성 평가와 유한요소해석 적용에 관한 연구

강성규(S. G. Kang),나영상(Y. S. Na),박규열(K. Y. Park),손선천(S. C. Son),이종훈(J. H. Lee) 한국정밀공학회 2005 한국정밀공학회 학술발표대회 논문집 Vol.2005 No.10월

Micro-forming is a suited technology to manufacture very small metallic parts(several mm~㎛). Micro-forming of Zr?₂Cu₁?Ni₁₃Al? bulk metallic glass(BMG) as a candidate material for this developing process are feasible at a relatively low stress in the supercooled liquid state without any crystallization during hot deformation. In this study, micro-formability of a representative bulk metallic glass, Zr?₂Cu₁?Ni₁₃Al?, was investigated for micro-forging of U-shape pattern. Micro-formability was estimated by comparing R<SUB>f</SUB> values (=A<SUB>f</SUB>/A<SUB>g</SUB>), where Ag is cross-sectional area of U groove, and A<SUB>f</SUB> the filled area by material. Microforging process was simulated and analyzed by applying finite element method. FEM simulation results should reasonable agreement with the experimental results when the material properties and simulation conditions such as top die speed, remeshing criteria and boundary conditions tightly controlled. The micro-formability of Zr?₂Cu₁?Ni₁₃Al? was increased with increasing load and time in the temperature range of the supercooled liquid state. Also, FEM Simulation using DEFORM was confirmed to be applicable for the micro-forming process simulation.

마이크로 단조를 이용한 Zr 계 벌크 비정질합금의 미세 성형성 평가와 유한요소해석 적용에 관한 연구

강성규(Sung Gyu Kang),나영상(Young Sang Na),박규열(Kyu Yeol Park),손선천(Seon Cheon Son),이종훈(Jong Hon Lee) Korean Society for Precision Engineering 2006 한국정밀공학회지 Vol.23 No.4

Micro-forming is a suited technology to manufacture very small metallic parts(several mm-㎛). Micro-forming of Zr?₂Cu₁?Ni₁₃Al? bulk metallic glass(BMG) as a candidate material for this developing process are feasible at a relatively low stress in the supercooled liquid state without any crystallization during hot deformation. In this study, micro￢formability of a representative bulk metallic glass, Zr?₂Cu₁?Ni₁₃Al? , was investigated for micro-forging of U-shape pattern. Micro-formability was estimated by comparing Rj values (=A<SUB>f</SUB>/A<SUB>g</SUB>), where A? is cross-sectional area ofU groove, and Ar the filled area by material. Micro-forging process was simulated and analyzed by applying finite element method. FEM simulation results showed reasonable agreement with the experimental results when the material properties and simulation conditions such as top die speed, remeshing criteria and boundary conditions were tightly controlled. The micro-formability of Zr?₂Cu₁?Ni₁₃Al? was increased with increasing load and time in the temperature range of the supercooled liquid state. Also, FEM simulation using a commercial software, DEFORM was confirmed to be applicable for the optimization of micro-forming process.

Plastic Deformation Mechanism of the Ti6Al4V Micro-gear Formed Under an Electrical Field

Bo Zeng,Xiangzhong Yan,Zhiqiang Xie,Jian Liu,Jie Wang,Kunlan Huang,Yi Yang 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.11 No.1

Despite the fact that titanium alloy micro-gear has superior performance and can withstand special conditions, it is difficult to machine due to its poor plasticity and high strength. We proposed an eco-friendly, efficient, and sustainable electric field assisted micro-plastic forming technology (micro-EFAPFT) for forming titanium alloy microparts. Ti-6Al-4 V alloy bars were extruded into micro-gears using an electrothermal coupling field and Joule heating in a graphite mold. The micro-gear has high precision, good surface quality, and a simple process. The whole process takes only 380 s. The findings demonstrate that the best gear forming degree, fewer microstructure defects, and hardness reaching 330.1 HV—4.4% higher than that of the raw material—occur when the pressure holding period is 120 s. During the plastic deformation process, phase transformation and recrystallization occur, increasing the fraction of α phase from 96.6–99.68% and increasing the grain orientation difference. The tooth tip has finer grains but longer dislocation lines. In conclusion, the electric field accelerates dislocation motion, reduces dislocation density, and increases material plasticity, allowing the Ti6Al4V micro-gear to be formed in a single step. The experimental results validate the feasibility of this technology for producing titanium alloy micro-gear and can be used to guide the production of different materials and shapes of microparts.