• Journal of the Korean Society for Precision Engineering
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• v.18 no.11
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• pp.74-79
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• 2001

In this two-part paper, a virtual machine tool (VMT) is presented. In part 1, the analytical foundation of a virtual machining system, envisioned as the foundation for a comprehensive simulation environment capable of predicting the outcome of cutting processes, is developed. The VMT system purposes to experience the pseudo-real machining before real cutting with a CNC machine tool, to provide the proper cutting conditions for process planners, and to compensate or control the machining process in terms of the productivity and attributes of products. The attributes can be characterized with the machined surface error, dimensional accuracy, roughness, integrity and so forth. The main components of the VMT are cutting process, application, thermal behavior and feed drive modules. In part 1, the cutting process module is presented. The proposed models were verified experimentally and gave significantly better prediction results than any other method. The thermal behavior and feed drive modules are developed in part 2 paper. The developed models are integrated as a comprehensive software environment in part 2 paper.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.1
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• pp.53-61
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• 1996

A clear understanding of the surface formation mechanism due to cutting is very important to help produce a good quality surface. Much of the roughness along the length of a bar being cut in a lathe can be explained in terms of macroscopic tool shape and feed rate. However, the roughness along the direction of cutting requires a different explanation. The formation of surface roughness is a problem in flow and fracture of materials in the vicinity of the tool edge. On a microscopic scale the cutting edge is rounded because it is impossible to grind a perfectly sharp cutting edge. Even if a perfectly sharp cutting edge were obtained it would soon become dull as a result of rapid breakdown and wear of the cutting edge. A research project is proposed in which in the main object is to model the surface formation mechanism due to cutting. The tool was assumed to be dull, that is, its edge has a finite radius. In order to study the effect of the radius of cutting edge on the surface formation, tools having different cutting edges were used. For orthogonal cutting experiment, cast iron and glass were chosen as brittle materials. Plowing forces acting in the cutting edge were estimated and its effect on the surface roughness was studied by observing the machined surface using optical microscope.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.311-311
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• 2011

$TiN{\times}$박막은 우수한 내마모성 및 내부식성, 높은 경도 그리고 열적 안정성 등으로 인하여, 절삭공구 및 기계적 부품의 하드코팅, 2차 연료 전지용 확산방지막의 코팅재료로서 광범위하게 사용되어지고 있다. 일반적으로 $TiN{\times}$ 박막은 화학 기상 증착법(CVD)을 이용하였으나, 최근에는 대면적에 균일한 코팅이 가능하고 기판과 박막상의 부착력이 우수하며, 프로세스를 제어하기 쉬운 물리적 기상 증착법(PVD)의 스퍼터링법에 대한 관심이 고조되고 있다. 그러나 스퍼터링법으로 증착된 $TiN{\times}$ 박막의 물성은 주상구조와 국부적 표면결함을 포함하는 박막의 미세구조에 의존하기 때문에 주상구조 사이에 존재하는 Void 와 Pinhole 그리고 crack들이 원인으로 작용하여, 내부식성 및 기계적 특성이 급속도로 저하되는 단점이 있다. 이러한 단점을 보완하기 위해서, 본 연구에서는 기판온도를(RT, $200^{\circ}C$, $400^{\circ}C$)증가시켜 실험 하였다. 이는 온도증가에 따른 박막의 치밀화가 이루어지고 결함이 감소하여 내부식성 특성향상이 기대되어진다. 또한 플라즈마 밀도를 높이기 위해서, 기존 DC 마그네트론 스퍼터링법에 전자기장을 추가로 인가하였다. 이는 플라즈마 밀도증가에 따른 고반응성의 질소 래디컬의 생성율 증가에 기인하여 박막 형성시 질화반응을 촉진시킴으로써 박막의 치밀화 및 내부식성 특성향상이 기대되어진다.

• Laser Solutions
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• v.12 no.1
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• pp.25-33
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• 2009

In laser-assisted machining (LAM), laser beam is used to locally increase the temperature of a workpiece and thus to enhance the machinability. In order to set the temperature of the material removal area of a workpiece at an optimal value, process parameters, such as laser power, feed rate, and rotational velocity, have to be carefully controlled. In this work, the effects of laser power and feed rate on the temperature distribution of a silicon nitride rotating at a constant velocity were experimentally investigated. Using a pyrometer, temperatures at various locations of the silicon nitride were measured both in circumferential and axial directions. The measured temperatures were fitted to a quadratic equation to approximate the temperature at the cutting location. The machining results showed that cutting force and tool wear were decreased when the temperature at the cutting location was increased.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.1
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• pp.16-22
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• 2018

Silicon carbide (SiC) is used in various semiconductor processes because it has superior thermal, mechanical, and electrical characteristics as well as higher chemical and corrosion resistance than existing materials. Due to these characteristics, various manufacturing technologies have been developed for SiC. A recent development among these technologies is Chemical Vapor Deposition SiC (CVD-SiC). Many studies have been carried out on the processing and manufacturing of CVD-SiC due to its different material characteristics compared to existing materials like RB-SiC or Sintered-SiC. CVD-SiC is physically stable and has excellent chemical and corrosion resistance. However, there is a problem with increasing the thickness, because it is manufactured through a deposition process. Additionally, due to its high strength and hardness, it is difficult to subject to machining.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.31 no.2
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• pp.11-18
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• 2008

Surface roughness is an important factor to evaluate machined parts in precision machining. This is the major measure of surface quality. This research sets up experiments to select the factors which affect surface roughness in the machining of inclined planes of aluminum. The levels of the selected experimental factors are chosen to evaluate the relationship between the surface roughness of the machined parts and machining parameters. This is to find out the optimal machining condition in the inclined planes. The objective of this research is to improve the surface roughness of the machined products by using the ANOVA analysis. The factors for the experiments are cutting speed, feed rate, cutting depth, and cutting width. The experimental levels of the factors are two for the cutting depth and width. For the cutting speed and feed rate, their levels are three because they are more sensitive for the surface roughness than the other two. The inclined planes are machined by 5-axis machining equipment.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.2
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• pp.73-78
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• 2011

The existent cutting insert have occupied most product of grinding style, because it has a problem of accuracy and manufacturing process. The product has a concept but development is difficult, because grinding and manufacturing by press are impossible. But by development and stabilization of a technology, preference of non-ground insert increases gradually. And then insert that grinding is impossible is developed availably as non-ground product by using developed equipment and software. In this paper reports some experimental results on the machining performance of non-ground Cutting inserts. Three kinds of Cutting inserts were manufactured without using grinding process. Machining experiments were carried out to compare the machining performance of non-ground inserts with that of ground ones. The experimental results indicate that the cutting forces and tool wear and surface roughnesses of machined surface of both ground and non-ground inserts are comparable.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.6
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• pp.629-635
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• 2009

In this research, KP-4, one of the plastic mold steels, was coated with the AlTiN from one layer to four layers by the PVD method in the $\Phi$ 8mm cemented carbide ball end mill. Coated KP-4 was processed with various conditions. For example, slope of $15^{\circ}$, $30^{\circ}$ and $45^{\circ}$ the spindle rotation speed was changed from 10,000rpm to 16,000rpm, the tool feeding speed was changed from 1,300mm/min to 1,700mm/min, the depth of cut was also changed from 0.3mm to 0.9mm, and etc. Cutting component force according to the coating layer number, and surface roughness were studied. The cutting component force showed a good agreement better the up ward direction than the down ward direction under all experimental conditions. In case of the condition per the material shape, it was lessen when the tool have larger angle because the average effective diameter of the tool is larger. The surface roughness showed good condition in case of the up ward than the down ward direction. And, in the 3rd layer of AlTiN coating, it showed the most suitable condition.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.2
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• pp.38-44
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• 2008

Titanium and its alloys, due to their superior properties of high specific strength and excellent corrosion resistance, are increasingly used in living applications in the 21century. The applications in aerospace and medical industries demand machining process more frequently to obtain a desired product. But unfortunately, this material is one of the most difficult-to-cut. In the turning process of titanium alloys, the key point for successful work is to select proper tool materials and cutting conditions. This study suggests a guidance for selecting the tool materials and the cutting speeds to improve tool life and surface integrity in Ti-6Al-4V titanium turning process. The experiments investigate the change of surface roughnesses, cutting forces and flank wear with various cutting parameters of tool materials, depth of cuts and feeds. As the results, K10 type of insert tip was assured as the best for turning of Ti-6Al-4V titanium alloy.

• Korean Journal of Metals and Materials
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• v.46 no.12
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• pp.835-840
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• 2008

Texturing for crystalline silicon solar cells is one of the important techniques to increase conversion efficiency by effective photon trapping. Generally, incoming wafers or alkali etched wafers are used for texturing. From this conventional etching process, $7{\sim}10{\mu}m$-sized random pyramids are formed. In this study, acid etching for removal of saw damages was practiced before texturing. This improved the resulting surface morphology, which consisted of $2{\sim}4{\mu}m$-sized pyramids. Because these pyramids covered the surface much more extensively, we obtained reduction of optical losses on the surface. In order to compare with conventional texturing, FE-SEM is used for observing surface morphology and reflectance data is analyzed by UV-VIS spectrophotometer.