• Transactions on Electrical and Electronic Materials
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• v.11 no.1
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• pp.33-36
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• 2010

$MgF_2$ is a current material used for optical applications in the ultraviolet and deep ultraviolet range. Process variables for manufacturing $MgF_2$ thin film were established in order to clarify the optimum conditions for the growth of the thin film, dependant upon the process conditions, and then by changing a number of the vapor deposition conditions, substrate temperatures, and heat treatment conditions, the structural and optical characteristics were measured. Then, optimum process variables were thus derived. Nevertheless, modern applications still require improvement in the optical and structural quality of the deposited layers. In the present work, in order to understand the composition and microstructure of $MgF_2$, single layers grown on a slide glass substrate using an Electron beam Evaporator (KV-660), were analyzed and compared. The surface substrate temperature, having an effect on the quality of the thin film, was changed from $200^{\circ}C$ to $350^{\circ}C$ at intervals of $50^{\circ}C$. The heat treatment temperature, which also has an effect on the thin film, was changed from $200^{\circ}C$ to $400^{\circ}C$ at intervals of $50^{\circ}C$. The physical properties of the thin film were investigated at various fabrication conditions, such as the substrate temperature, the heat treatment temperature, and the heat treatment time, by X-ray diffraction, and field emission-scanning electron microscopy.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.536-542
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• 2002

There are two important variables in machining process control, which are feed and cutting speed. In this work, a two degree-of-freedom controller is designed and implemented to achieve on-line cutting force control and position control based on the modelling of cutting process dynamics which are established through step response test. Two schemes are proposed and implemented. The first is feed control under the constant spindle speed and spindle speed control under the constant feed speed. The second is a simultaneous control of feed and spindle speed. The last performs a position control under the constant cutting force. Those are confirmed to work properly. Especially the latter shows a faster response.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.03a
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• pp.172-184
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• 1996

Superplastic forming of thin sheet into complex shape is an important manufacturing process especially in aerospace industry. The main interest in modeling the superplastic forming process is to predict the forming pressure cycle to maintain optimum strain rate and the resulting thickness distribution. Many researchers have attemped to model superplastic forming using the various techniques including finite element method. But in most of their researches have disregarded the strain hardening effect which which occurs in several superplastic materials. In this study ABAQUS finite element code was used for prediction of process variables for axisymmetric cup forming of Supral 100 and 7075Al alloys considereing strain hardening. The performance of numerical results were compared with the experimental results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.1016-1020
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• 2001

The spinning is a very effective manufacturing technology for short production runs in a variety of sizes and shapes, because it can form the cross-section or tubular parts various shapes. However extensive experimental and analytical research has not been carried out. In this study, and fundamental experiment was conducted to improve productivity with process parameter such as tool path, angle of roller holder(a), feed rate(v) and corner radius of forming roller(Rr). These factors were selected as variables in the experiment because they were most likely expected to have and effect on spring back. The clearance was controlled in order to achieve the precision product which is comparable to deep drawing one. And also thickness and diameter distribution of a multistage cup obtained by shear spinning process were observed and compared with those of a commercial product produced by conventional deep drawing.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.1
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• pp.12-18
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• 2008

This paper describes two run-to-run controllers, a nonlinear multiple exponential-weight moving-average (NMEWMA) controller and a dynamic model-tuning minimum-variance (DMTMV) controller, for photolithography processes. The relationships between the input recipes (exposure dose and focus) and output variables (critical dimensions) were formed using an experimental design method, and the photolithography process model was built using a multiple regression analysis. Both the NMEWMA and DMTMV controllers could update the process model and obtain the optimal recipes for the next run. Quantified improvements were obtained from simulations and real photolithography processes.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.4
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• pp.29-35
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• 2007

The main objective of this paper is to propose the optimal design method of forging process using genetic algorithm. Design optimization of forging process was doing about one stage and multi stage. The objective function is considered the filling of die. The chosen design variables are die geometry in multi stage and initial billet shape in one stage. We performed FE analysis to simulated forging process. The optimized preform and initial billet shape was obtained by genetic algorithm and FE analysis. To show the efficiency of GA method in forging problem are solved and compared with published results.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.6
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• pp.465-470
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• 2003

The chemical mechanical polishing (CMP) process has been widely used for the global planarization of multi-layer structures in semiconductor manufacturing. The CMP process can be optimized by several parameters such as equipment, consumables (pad, backing film and slurry), process variables and post-CMP cleaning. However, the COO(cost of ownership) is very high, because of high consumable cost. Especially, among the consumables, the slurry dominates more than 40 %. In this paper, we have studied the CMP characteristics of diluted silica slurry by adding of raw alumina abrasives and annealed alumina abrasives. As an experimental result, we obtained the comparable slurry characteristics compared with original silica slurry in the view-point of high removal rate and low non-uniformity. Therefore, we can reduce the cost of consumables(COC) of CMP process for ULSI applications.

• Tribology and Lubricants
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• v.18 no.5
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• pp.345-350
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• 2002

Recently, as the development of manufacturing technique on SMC(sheet molding compound), various numerical and experimental approaches to injection and compression molding have been investigated. Injection and compression molding, however, has so various cases with complicated boundary condition that it is difficult to analyze mold characteristics precisely. In addition, since a slight change in process variables can significantly change the resulting mold thickness, a proper design is important to compression molding process. Therefore, in this study, the effects of various parameters on compression molding process have been investigated using FEM(finite element method) to formulate the melt front advancement during the mold filling process. To verify the results of present analysis, they are compared with those of reference. The results show a strong effect of initial charge volume, injection time and pressure as a result of variations in the rectangular charge shape.

• Laser Solutions
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• v.3 no.3
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• pp.13-19
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• 2000

The stencil is a thin stainless sheet in which a pattern is formed, which is placed on a surface of plate to reproduce the pattern of electric circuit. Conventionally the stencil has been produced by etching process. This process has many anti-environmental factors. In this study, Nd : YAG laser cutting process has been applied for stencil manufacturing. The study is focused on estimating kerf width of laser cut stencil by E.B.P.(Error Back-Propagation). This algorithm is good for estimating target value from input value. In this paper, target value was kerf width, and input values were frequency, pulse width, cutting speed and laser power. E.B.P. after teaming input and target could estimate kerf width from some variables precisely.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.04a
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• pp.287-292
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• 2004

In this study, we made a comparative study of backpropagation neural network and probabilistic neural network and bayesian classifier and perceptron as shape recognition algorithm of welding flaws. For this purpose, variables are applied the same to four algorithms. Here, feature variable is composed of time domain signal itself and frequency domain signal itself, Through this process, we confirmed advantages/disadvantages of four algorithms and identified application methods of few algorithms.