• 한국공작기계학회논문집
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• 제15권2호
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• pp.73-80
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• 2006

This paper describes a analysis on the chip thickness model required for cutting force simulation in ball-end milling. In milling, cutting forces are obtained by multiplying chip area to specific cutting forces in each cutting instance. Specific cutting forces are one of the important factors for cutting force predication and have unique value according to workpiece materials. Chip area in two dimensional cutting is simply calculated using depth of cut and feed, but not simply obtained in three dimensional cutting such as milling due to complex cutting mechanics. In ball-end milling, machining is almost performed in the ball part of the cutter and tool radius is varied along contact point of the cutter and workpiece. In result, the cutting speed and the effective helix angle are changed according to length from the tool tip. In this study, for chip thickness model analysis, tool and chip geometry are analyzed and then the definition of chip thickness and estimation method are described. The resulted of analysis are verified by compared with geometrical simulation and other research. The proposed chip thickness model is more precise.

• 한국재료학회지
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• 제18권5호
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• pp.247-252
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• 2008

A laser glass cutting system using a femto-second laser was evaluated for Flat Panel Display (FPD) glass. A theoretical analysis of the ablation threshold and depth is described using an explicit analytic form. Experiments for clean and deep grooves were performed using a 3W femto-second laser, and the relationships between the input energy and the scribing depth as well as the threshold energy are presented. Mechanical breaking after the scribing process was carried out and the results are compared with a theoretical method. It was found that a two-sided LCD panel glass can be cut clearly using the laser cutting method. The methodology was found to be very effective as a mass-production cutting system.

• 한국기계가공학회지
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• 제2권3호
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• pp.20-25
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• 2003

The End-milling has been widely used in the industrial world because it is effective to cutting working with various shape. Recently the end-milling is demanded the high-precise technique with good surface roughness and rapid manufacturing time for precision machine and electronic elements. The cutting working of end-milling such as, cutting direction, revolution of spindle, feed rate and depth of cut have an effect on optimum surface roughness. This study was carried out to decide the working condition for optimum surface roughness and rapid manufacturing time by design of experiment and ANOVA. From the results of this study, the optimum working condition for end milling is upward cutting in cutting direction, 600rpm in revolution of spindle, 240mm/mm in feed rate, 2mm in axial depth of cut and 0 25mm in radial depth of cut. The design of experiment has become an useful method to select optimum working condition mend-milling.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.1338-1345
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• 2009

Although rock excavation is necessary for the effective utilization of urban space, most conventional rock excavation methods, including the blasting method, cause high noise and vibration. Meanwhile, if a high pressure waterjet system is applied to excavate underground spaces in urban areas, the public grievance can be reduced by low noise and vibration. In this study, an abrasive waterjet system is designed and developed to study the influence of various performance parameters such as jet pressure, nozzle traverse speed, stand-off distance, or abrasive feed rate on waterjet excavation performance in laboratory. Using the developed waterjet system, rock drilling characteristics are identified by measuring drilling depths as a function of the jet exposure time. The drilling depth linearly increases with increasing the jet exposure time(under 60sec). Rock cutting characteristics are also obtained with various jet pressures(1600~3200kg/$cm^2$) and nozzle traverse speeds(1.9~14.1mm/s): The cutting depth is nonlinearly related to the jet pressure and traverse speed. Indeed, the cutting depth increases with an increase in the jet pressure and a decrease in the nozzle traverse speed. This trend can be explained by energy transferring/loss mechanism.

• Journal of Welding and Joining
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• 제23권1호
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• pp.86-93
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• 2005

Abrasive waterjet (AWJ) can provide a more effective means for precision of difficult -to-machining materials such as ceramics and titanium alloys. The present study is focused on the surface roughness of abrasive waterjet cut surfaces. This paper investigated theoretical and experimental surface characteristics associated with abrasive waterjet cutting of titanium alloy Gr2. It is shown that the proper variations of several cutting parameters such as waterjet cutting pressure, cutting speed and cutting depth improve the roughness and characteristics on specimen surfaces produced by AWJ cutting. From the experimental results by AWJ cutting of titanium alloy Gr2, the optimal cutting conditions to improve the surface roughness and precision were proposed and discussed.

• 한국기계가공학회지
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• 제3권2호
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• pp.25-31
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• 2004

Machinability in metal cutting processes depends on cutting input conditions such as cutting velocity, feed rate, depth of cut, types of work material and tool shape factors. In this study, to assess chip breaking characteristics of a turning process, an equivalent oblique cutting system to this has been established. And the equivalent effective rake angle was determined using side rake angle, back rake angle and side cutting edge angle of the tool. A non-dimensional parameter, Chip breaking index(CB), was used to assess Chip breaking characteristics of chip in conjunction with the equivalent effective rake angle. In case of positive rake angles of the equivalent effective rake, the back rake angle has little effect on the chip breaking characteristics however, in case of negative ones, the side rake angle has some effect on Chip breaking characteristics.

• 한국정밀공학회지
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• 제1권2호
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• pp.24-32
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• 1984

The object of the study is to discuss the effect of magic ink as a surface active substance on the mechanism of chip formation in oblique cutting. The Rehbinder effect has been known as a phenomenon that the mechanical strength reduces when the metal is coated with some surface active substances. In order to interpret these surface effects defined by Rehbinder, the influence on the shear strength of shear plane by coating surface active substances, cutting force by the depth of cut, surface roughness and hardness ratio were observed. The results are as follows: 1. By coating the magic ink on free surface of the forming chip, the effective shear angle increases, and the cuttinbg force and the deformed chip thickness decreases. 2. With the large inclination angle the effective shear angle increases, and the specific cutting force and the friction angle decrease. 3. Cutting of the coated surface improves the surface roughness and the hardness ratio drops, which means another Rehbinder effect.

• 한국지반환경공학회 논문집
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• 제6권2호
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• pp.15-20
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• 2005

도로 주변 절토사면 상부에 시공되는 산마루 측구는 상부로부터 흘러내리는 지표수를 원활히 배수시켜 절개면으로 유입되는 것을 방지한다. 국내의 경우 전 국토의 70%이상이 산악지로 구성되어 있어 도로 개설에 따른 절개면의 발생은 필연적이다. 여름 집중호우와 간극수압의 증가로 인하여 절개면의 불안정성은 증가된다. 그러나 절토사면 상부에 시공되어 있는 산마루측구는 품질관리의 어려움과 배수능력 부족 등의 문제점들이 있다. 따라서, 본 논문에서는 산마루 측구의 깊이와 투수계수에 따른 절토사면의 안전율 변화를 분석하였으며 적절한 측구 설치깊이를 결정하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1338-1343
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• 2007

High-efficient machining, which means cutting a part in the least amount of time, is the most effective tool to improve productivity. In this study, a new feed optimization method based on the cutting power regulation was proposed to realize the high-efficient machining in turning process. The cutting area was evaluated by using the Boolean intersection operation between the cutting tool and workpiece. And the cutting force and power were predicted from the cutting parameters such as feed, depth of cut, spindle speed, specific cutting force, and so on. Especially, the reliability of the proposed optimization method was validated by comparing the predicted and measured cutting forces. The simulation results showed that the proposed optimization method could effectively enhance the productivity in turning process.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.332-338
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• 2000

The high speed machining is now one of the most effective manufacturing methods to achive higher productivity. However, due to the increased cutting temperatures caused by increased cutting speed, tool wear become larger. Especially in high speed face milling, cutting tools are exposed not only to high cutting temperatures, but also to mechanical and thermal shock stresses. It is essential, therefore, to know the wear characteristics of tool materials in high speed machining. This study presents an experimental investigation of the cutting performance of CBN tools in high speed face milling of gray cast iron FC25. The effect of cutting conditions and cutting length on flank wear of CBN tools and roughness of machined surfaces is investigated. The cutting parameters involved were ; cutting speeds in the range of 600to 1800 m/min, feed of 0.1 mm/tooth, and depth of cut of 0.3mm.