• 한국기계가공학회지
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• 제18권10호
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• pp.60-67
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• 2019

Recently, lightweight materials such as Ti alloys have been used increasingly in the aerospace and high-tech industries for weight loss and fuel efficiency. Because of built-up edges and workpiece deflection due to low stiffness, the Ti alloys have poor machinability. In our study, systematic experiments were conducted to investigate the milling characteristics of the Ti alloy (Ti-6A1-4V) with endmills. The independent variables in the experiment were spindle speed, feed per tooth, and axial depth. Cutting force, acceleration RMS, and surface roughness were measured. Using the response surface method, the optimal cutting conditions were analyzed to improve machining quality and productivity.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권1호
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• pp.294-306
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• 2019

On the basis of the Computational Fluid Dynamics technique (CFD) combined with the overlap grid method, this paper establishes a numerical simulation method to study the problem of ice-propeller interaction in viscous flow and carries out a simulation forecast of the hydrodynamic performance of an ice-class propeller and flow characteristics when in the proximity of milling-shape ice (i.e., an ice block with a groove cut by a high-speed revolving propeller). We use a trimmed mesh in the entire calculation domain and use the overlap grid method to transfer information between the domains of propeller rotation calculation and ice-surface computing. The grid is refined in the narrow gap between the ice and propeller to ensure the accuracy of the flow field. Comparison with the results of the experiment reveals that the error of the hydrodynamic performance is within 5%. This confirms the feasibility of the calculation method. In this paper, we calculate the exciting force of the propeller, analyze the time domain of the exciting force, and obtain the curve of the frequency domain using a Fourier transform of the time-domain curve of the exciting force. The existence of milling-shape ice before the propeller can greatly disturb the wake flow field. Unlike in open water, the propeller bearing capacity shows a downward trend in three stages, and fluctuating pressure is more disordered near the ice.

• 한국기계가공학회지
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• 제20권11호
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• pp.52-59
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• 2021

Titanium alloy (Ti-alloy) is widely used as a material for core parts of aircraft structures and engines that require both lightweight and heat-resistant properties owing to their high specific stiffness. Most parts used in aircraft have I-, L-, and H-shaped thin-walled structures for weight reduction. It is difficult to machine thin-walled structures owing to vibrations and deformations during machining. In particular, cutting tool damage occurs in the corners of thin-walled structures owing to the rapid increase in cutting force and vibration, and machining quality deteriorates because of deep tool marks on machined surfaces. In this study, milling experiments were performed to derive an effective method for machining a L-shaped thin-walled structure with Ti-alloy (Ti-6Al-4V). Three types of machining experiment were performed. The surface quality, tool wear, cutting force, and vibration were analyzed comprehensively, and an effective machining method in terms of tool life and machining quality was derived.

• 한국식품과학회지
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• 제10권2호
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• pp.109-111
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• 1978

보리, 쌀보리, 밀등 3종(種)의 국산맥류(國産麥類)를 공시(公試)하여 도정(搗精)과 제분(製粉)의 두가지 가공방법(加工方法)으로 가공수율(加工收率) 60%, 70%, 80%, 90%의 네 수준(水準)으로 나누어 회분(灰分), 단백질(蛋白質), 지질(脂質) 섬유질(纖維質), Calcium, 철분(鐵分), Thiamine등의 함유율(含有率)을 분석(分析) 조사(調査)하였던바 다음과 같은 결과(結果)를 얻었다. 1) 가공(加工)된 곡물(穀物)의 회분(灰分), 단백질(蛋白質), 지질(脂質), 섬유질(纖維質), Calcium, 철분(鐵分), Thiamine등의 함유율(含油率)은 도정(搗精)의 경우 제분(製粉)의 경우에 다 같이 가공수율(加工收率)과 정비례관계(正比例關係)에 있었다. 2) 겉보리에서는 도정(搗精)한 것이 제분(製粉)한 것에 비(比)해 평균적(平均的)으로 동일(同一)한 가공수율(加工收率)에서 회분(灰分)은 0.83%, 단백질(蛋白質)은 1.31%, 지질(脂質)은 0.40%, 섬유질(纖維質)은 0.75%, Calcium은 3.03mg%, 철분(鐵分)은 2.40mg%, Thiamine은 0.14mg%가 낮았다. 3) 쌀보리에서는 도정(搗精)한 것이 제분(製粉)한 것에 비(比)해 평균적(平均的)으로 동일(同一)한 가공수율(加工收率)에서 회분(灰分)은 0.41%, 단백질(蛋白質)은 1.96%, 지질(脂質)은 0.33%, 섬유질(纖維質)은 0.84%, Calcium은 4.54mg%, 철분(鐵分)은 1.19mg%, Thiamine은 0.10mg%가 낮았다. 4) 밀에서는 도정(搗精)한 것이 제분(製粉)한 것에 비(比)해 평균적(平均的)으로 동일(同一)한 가공수율(加工收率)에서 회분(灰分)은 0.28%, 단백질(蛋白質)은 2.25%, 지질(脂質)은 0.05%, 섬유질(纖維質)은 0.25%, Calcium은 4.31mg%, 철분(鐵分)은 0.12mg%, Thiamine은 0.15mg%가 높았다.

• Journal of Mechanical Science and Technology
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• 제16권7호
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• pp.873-881
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• 2002

In this paper, a on-line estimation method of the radial immersion angle using cutting force is presented. The ratio of cutting forces in feed and cross-feed directions acting on the single tooth at the immersion angle is a function of the immersion angle and the ratio of radial to tangential cutting force. It is found that the ratio of radial to tangential cutting force is not affected by cutting conditions and axial rake angle, which implies that the ratio determined by one preliminary experiment can be used regardless of the cutting conditions for a given tool and workpiece material. Using the measured cutting force during machining and predetermined ratio, the radial immersion ratio is estimated in process. Various experimental results show that the proposed method works within 5% error range.

• 대한기계학회논문집
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• 제15권1호
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• pp.78-89
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• 1991

본 연구에서는 ARSC를 엔드밀링 공정에 적용하여, 절삭력을 추종제어하는 실 예를 제시하고자 한다.제2장에서는 ARSC를 절삭공정에 일반적으로 적용하기 위한 구체적인 이론전개를 설명하여, 제3장에 실시간 시뮬레이션의 방법과 결과를 예시하 고,마지막으로, 제4장에 엔드밀링 절삭시험을 위한 장치의 구성 및 그 결과를 설명하 였다.

• 한국기계가공학회지
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• 제10권1호
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• pp.1-7
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• 2011

Micromachining is gaining popularity due to recent advancements in MEMS(Micro Electro Mechanical Systems). Using conventional micromachining, it is relatively difficult to produce moving components in the order of microns. Photolithography for silicon material has high accuracy machining, but it has low aspect ratio. X-ray lithography has ultra high accuracy machining, but it has expensive cost. Micro-EDM(electro discharge machining) has been gaining popularity as a new alternative method to fabricate micro-structures. In this study, Micro-EDM machine is developed available for fabricate micro-structures and two processes such as side cut EDM and milling EDM is proposed. Several sets of experiment results have been performed to study the characteristics of the machining process.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1993년도 추계학술대회 논문집
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• pp.321-327
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• 1993

In order to maintain the cutting force at a desired level during peripheral end milling processes in spite of variation of the depth of cut and other machining conditions, a feedrate override. Apaptive Control Constraint (ACC) system are developed. Feedrate override was accomplished by a developed MMC board and PMC interface techniques. Nonlinear model of the cutting process was linearized as an adaptive model with time varying paramrters. Integral type estimators were introduced for on-line identification of cutting and control parameters in peripheral and milling processes. Zero Order Jold (ZOH) type degital control methodology which uses pole-placement concepts was applied for the ACC system. Performance of the developed ACC system was confirmed on the vertical machining center equipped with FANUC OMC for a large amount of experiment

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1531-1534
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• 2005

Nano pattern is being utilized to produce micro optical components, sensors, and information storage devices. In this study, a study on nano pattern fabrication using raster-scan type Focused Ion Beam (FIB) milling is introduced. Because the intensity of ion beam has Gaussian distribution, the overlapping of the Gaussian beam results in a 3D pattern, and the shape of the pattern can be adjusted by variation of FIB milling parameters, such as overlap, ion dose, and dwell time. The Gaussian shape of single beam intensity has been investigated by experiment, and 3D nano patterns with pitch of 200nm generated by FIB is demonstrated.

• 제어로봇시스템학회논문지
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• 제2권4호
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• pp.351-361
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• 1996

A variable structure controller is developed for an AC servo motor used in CNC milling machines. The designed controller is implemented as an outer loop controller to a factory designed motor-servopack system. The robustness parameter is tuned for a fast response when the speed tracking error is large, while it is tuned for small oscillations when the speed tracking error is small. The designed controller is installed on a CNC machine using a PC. Cutting experiments show improved performance over the factory-designed controller.