• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.12
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• pp.1088-1095
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• 2008

5-axis NC machining has a good advantage of the accessibility of tool motion by adding two rotary axes. It offers numerous advantages such as expanding machining fields in parts of turbo machineries like impeller, propeller, turbine blade and rotor, reasonable tool employment and great reduction of the set-up process. However, as adding two rotary axes, it is difficult to choose suitable machining conditions in terms of tool path, tool posture, feedrate control at a tool tip and post-processing. Therefore in this paper, it is proposed to decide suitable machining condition through an experimental method such as adopting various tool paths, tool postures, and feedrate types. Machining experiment on AL7075 for impeller is performed to define suitable machining condition, and measurement of surface roughness on machined surfaces depended on each machining condition is performed. By defining suitable machining condition, we should have conclusion as improving the surface quality in the aspect of surface roughness and machined shape of surface.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.2
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• pp.137-143
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• 2022

Composite materials, being light-weight and of high mechanical strength, are increasingly used in various industries such as the aerospace, automobile, sporting-goods manufacturing, and ship-building industries. Recently, manufacturing of composite materials using 3D printers has increased. 3D-printed composite materials are made in free-form and adapted for end-use by adjusting the fiber content and orientation. However, research on the machining of 3D printed composite materials is limited. The aim of this study is to develop a machine learning method to select machining conditions for machining of 3D-printed composite materials. The composite material was composed of Onyx and carbon fibers and stacked sequentially. The experiments were performed using the following machining conditions: spindle speed, feed rate, depth of cut, and machining direction. Cutting forces of the different machining conditions were measured by milling the composite materials. PCA, a method of machine learning, was developed to select the machining conditions and will be used in subsequent experiments under various machining conditions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.2
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• pp.213-218
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• 2013

Ultrasonic machining (USM) is a new method used in metal cutting. This process does not involve heating or any electrochemical effects, causes low surface damage, has small residual stress, and does not rely on the conductivity of the workpiece. These characteristics are suitable for the machining of brittle materials such as glass or ceramics. However, the use of USM for brittle materials generates cracks on the workpiece. Therefore, in this study, Taguchi's method was used to optimize the processing conditions of micro holes drilled in glass and ceramics. This method was used to successfully reduce the number of cracks at the entrance and the exit of the micro holes.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.10
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• pp.1039-1045
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• 2007

Ultrasonic machining (USM) is suitable for machining hard, brittle and non-conductive materials such as silicon, glass and ceramics. Usually, when micro holes are machined on glass by USM, roundness of hole entrance is poor and cracks appear around the hole exit. In this paper the machining characteristics were studied for roundness improvement and exit crack prevention. From experiments, the tool bending and the shape of tool tip affect hole roundness. When the tool tip is hemispherical, good roundness of holes was obtained. The feedrate and the rotational speed of the tool affect the exit crack. With the machining conditions of 150 rpm in spindle speed and $0.5\;{\mu}m/s$ in feedrate, micro holes with less than $100\;{\mu}m$ in diameter were machined without an exit crack.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.8
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• pp.2073-2080
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• 1994

In this paper, a model of material removal in abrasive water jet machining of brittle material is developed, and experimentally evaluated. Abrasive water jet machining proved to yield better material removal rate than other machining techniques for hard and brittle material (alumina ceramics). It was also found that large scale fracture may develop at the exit of the jet from the material. The fracture size was predicted as a function of water jet pressure and size of the hole. Finally, the feasibility of using acoustic emission signals for in-process monitoring of the abrasive water jet machining process is investigated.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.8
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• pp.1832-1843
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• 1995

Tool interference is one of the most critical problems in sculptured surface machining. When machining cavities and concaves, the tool frequently overcuts the portions of the surface, which cause inaccuracy in machining. So tool interference-free paths must be generated for rough cutting more efficiently. In this paper a software using SSI(Surface/Surface intersection) algorithm is developed for eliminating tool interference which occurs in an offset surface in 3-dimensional free form surface modeling. this work consists of two stages : using the offset data, the intersection curves are rapidly checked by this algorithm at the first stage. CL(cutter location) data are obtained by deleting the loop section of intersected offset patches at the second stage. This algorithm can reduce the amount of memory required to store machining data and also easily check region which have the possibility of intersection. Also, This software is verified to be useful in machining a curved object on a DNC milling machine.

• Transactions of the Korean Society of Mechanical Engineers
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• v.5 no.4
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• pp.338-346
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• 1981

Honing, lapping, polishing and superfinishing are applied for a precision machining to finish the metal surface, but these precision machining are micro-cutting by hard and micro-abrasive grains. Frictional machining is the new method to finish mirrorlike surface without using those abrasive grains. The frictional machining produces high pressure and high temperature instantly by compressing a tool material against the metal surface in sliding motion. The metal surface is given plastic deformation and plastic flow by the above mentioned frictional motion, but the surface roughness of the metal surface is influenced by physical and chemical reaction in surrounding atmosphere. Therefore, the atmosphere around the metal optimum atmosphere in the frictional machining. The part 1 of the study was performed in liquid atmospheres. Diesel oil, lubricant, grease, lard oil, bean oil and cutting fluid were used as such atmospheres. Medium carbon steel SM 50 C was used as a workpiece and ceramic tip was applied as a frictional tool. The result of the experiment showed characteristic machining conditions to generate the best surface roughness in each atmospheres.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.6
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• pp.421-425
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• 2016

Micro-EDM is one of the recent fine-machining technologies. Micro-EDM is widely used in precision processes because products manufactured via EDM are free from workpiece hardness. However, the debris produced during the process cause many problems such as reduced precision of the process. The first solution of this problem involves using the milling hole process. Micro-EDM hole process involves an electrode moving rapidly in the vertical direction via a servo system to disperse debris. However, this process can cause reduced work efficiency owing to contact between the electrode and workpiece. In this study, ultrasonic vibration is added to micro-EDM channel machining. Ultrasonic vibration removes the debris during machining and enables precision machining. Consequently, a clean work environment for the subsequent processes is maintained.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.9
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• pp.53-57
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• 2009

There are technical requirements to manufacture large size functional parts with not only simple geometries like a flat or spherical surface but also sculptured geometries. In addition, the required machining accuracy for these parts is becoming more severe. In general, the form accuracy of machined parts is determined by the relative position between workpiece and tool during machining process. To improve machining accuracy the relative position errors should be maintained within the required accuracy. This study deals with the estimation and calibration of depth of cut using the AE signal in micro-machining. Also, this sensing technique can be applied to detect the initial contact between workpiece and tool.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.3
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• pp.468-484
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• 1992

본 연구에서는 기존의 유연 볼 엔드밀의 절삭력 모델을 바탕으로 자유 곡면의 정삭 가공에서 발생할 수 있는 과대 또는 과소 절삭을 방지하면서 그 가공의 효율성을 높이기 위한 볼 엔드밀의 이송 속도 결정법을 제시하고자 한다. 먼저, 자유 곡면의 가공에서 발생될 수 있는 공구의 처짐에 따른 가공오차에 대하여 볼 엔드밀 공구의 처 짐벡터와 공작물의 공구 접촉점에서의 법선벡터로 표현되는 가공오차(machining error ) 예측 모델식을 유도하였다. 본 가공오차 예측 모델식은 다시 절삭날당 가지는 이 송량의 함수로 전개되어 그 곡면의 주어진 가공 공차(machining tolerance)를 만족시 키는 이송속도를 결정하게 된다.