• 한국정밀공학회지
• /
• 제16권2호통권95호
• /
• pp.234-243
• /
• 1999

Using the geometric and the vector methods, three dimensional surface texture and roughness models in flat end milling are developed. In these models, rear cutting effect on surface generation is considered along with tool run-out and tool setting error including tool tilting and eccentricity between tool center and spindle rotational center. Rear cutting is the secondary cutting of the already machined surface by the trailing cutting edge. The effects of tool geometry and tool deflection on surface roughness are also considered. For representing the surface texture more practically, three dimentional surface topography parameters such as RMS deviaiton, skewness and kurtosis are introduced and used in expressing the surface texture characteristics. Under various cutting conditions, it is confirmed that the developed models predict the real surface profile precisely. These models could contribute to the cutter design and cutting condition selection for the reduction of machining and manual finishing time.

• 대한기계학회논문집A
• /
• 제24권10호
• /
• pp.2597-2602
• /
• 2000

The most effective means of evaluating remaining life is through the creep testing of samples removed from the component. But sampling of large specimen from in-service component is actually impossible. So, sampling device and small-specimen creep tester have been applied. Sampling device has been devised to extract mechanically small samples by hemispherical, diamond -coated cutter from the surface of turbine rotor bores and thick-walled pipes without subsequent weld repairs requiring post weld heat treatment. A method of manufacturing small creep specimen, 2min gage diameter and 10min gage length, using electron beam welding to attach grip section, has been proven. Small-specimen creep tester has been designed to control atmosphere to prevent stress increment by oxidation during experiment. To determine whether the small specimens successfully reproduce the behavior of large specimens, creep rupture tests for small and large specimens have been performed at identical conditions. Creep rupture times based on small specimens have closely agreed within 5% error compared with that of large specimen. The errors in rupture time have decreased at longer test period. This comparison validates the procedure for fabricating and testing on small specimen. This technique offers potential as an efficient method for remaining life assessment by direct sampling from in -service high temperature components.

• 한국CDE학회논문집
• /
• 제6권2호
• /
• pp.89-100
• /
• 2001

Swept volume is the sweeping region of moving objects. It is used in various applications such as interference detection in assembly design, visualization of manipulator motions in robotics, simulation of the volume removal by a cutter in NC machining. The shape of swept volume is defined by the envelope, which is determined by the boundary of moving objects and its direction of motion. In order to implement the generation of swept volume, researchers have taken much effort to develop the techniques how to generate the envelope. However, their results are confined to envelope generated only in simple shape objects, such as polyhedra or quadric surfaces. This study provided the envelope generation algorithm of NURBS objects. Characteristic points were obtained by applying the geometric conditions of envelope to NURBS equations, and then characteristic curves were created by means of interpolating those points. Silhouette edges were determined in the following procedures. First, two adjacent surfaces which have the same edge were found from B-Rep data. Then, by taking the scalar product of velocity vector of a point on that edge with each normal vector on two surfaces, silhouette edges were discriminated. Finally, envelope was generated along moving direction in the form of ruled surfaces by using both the partial information between initial and final position of objects affecting envelope along with characteristic curves and silhouette edge. Since this developed algorithm can be applied not only to NURBS objects but also to their Boolean objects, it can be used effectively in various applications.

• Journal of Computational Design and Engineering
• /
• 제2권4호
• /
• pp.233-247
• /
• 2015

In this paper, the cutting force calculation of ball-end mill processing was modeled mathematically. All derivations of cutting forces were directly based on the tangential, radial, and axial cutting force components. In the developed mathematical model of cutting forces, the relationship of average cutting force and the feed per flute was characterized as a linear function. The cutting force coefficient model was formulated by a function of average cutting force and other parameters such as cutter geometry, cutting conditions, and so on. An experimental method was proposed based on the stable milling condition to estimate the cutting force coefficients for ball-end mill. This method could be applied for each pair of tool and workpiece. The developed cutting force model has been successfully verified experimentally with very promising results.

• 한국분무공학회지
• /
• 제14권1호
• /
• pp.34-38
• /
• 2009

This paper presents the pulsation of carburetor inlet and outlet pressure of a small SI gasoline engine. The engine used in this paper is a 23cc, single cylinder, diaphragm carburetor, two-stroke, air-cooled for brush cutter. The rpm and pressure wave pulsation at the inlet and the outlet of carburetor were measured and analysed for the understand of the internal air flow into the barrel on the diaphragm carburetor. These data should be used for the development of the duel fuel injection system for gasoline and LPG. The results showed that the carburetor inlet pressure variations were very steady, but the pressure variations at carburetor outlet were very sensitive to the pressure variation into the crank case and were to similar independently to the engine speed on partial opened throttle conditions. According to increasing engine speed, the pressure waves started to come out and be developed after closing the intake port of the engine at carburetor outlet. Reverse flow occurred on the WOT (wide open throttle) condition.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2008년도 춘계학술대회논문집
• /
• pp.409-412
• /
• 2008

This paper presents the effects of excess air factors(0.84${\sim}$0.90) and opened throttle area ratios(AR=0.15${\sim}$0.25) on the emission and performance of a small spark-ignition gasoline engine. The engine used in this paper was a single cylinder, diaphragm carburetor, two-stroke, air-cooled 26cc engine for brush cutter. The rpm, torque, fuel consumption and CO emission were measured under the four different excess air factors and three different opened area ratios conditions on the engine loads respectively. The results showed that the rpm was decreased and torque was increased at increasing load, the maximum power and minimum fuel consumption could be obtained critical rpm on each throttle opened area ratios and brake specific fuel consumption was decreased 13${\sim}$17%, CO emissions was decreased 21${\sim}$38% at excess air factor 0.90 than 0.84.

• 대한기계학회논문집
• /
• 제9권5호
• /
• pp.572-578
• /
• 1985

본 논문에서는 인벌류우트와 원고치형의 단점을 보완하고 양자의 장점을 취한 치형을 얻기위하여 피치점 부근에서는 인벌류우트치형으로 이끝부분에서는 원호로 하 고 이뿌리부분에서는 상대방 기어의 원호부분과 맞물릴 수 있는 곡선으로 하는 치형을 합성하고, 이 합성치형의 유효치형을 가공할 수 있는 랙치형을 이론적인 방법으로 구 하였다. 그리고, 이 합성치형의 유효치형에 대한 이끝과 이뿌리 두께의 변화와 물림 률을 검토하였다.

• 한국기계가공학회지
• /
• 제15권4호
• /
• pp.101-108
• /
• 2016

Endmill fillet cutting at the corner was conducted with the online measurement of cutting forces and tool deflection by a tool dynamometer and an eddy current sensor system. The profile of the machined surface was also compared with the CAD profile with a Coordinate Measuring Machine (CMM) and CALYPSO software. It was found that the end mill cutter with four blades has a better surface profile than that with two blades, and the cutting forces and tool deformation were increased as the cutting speed was increased. When the tool located at the degree $45^{\circ}$ corner was found to conduct the maximum cutting force than started to the point of the workpiece. As it was compared with the CMM and ANOVA analysis result in the case that the cutting force and tool deformation was the maximum, it was found that the result was affected by the spindle speed and the number of blades.

• 패션비즈니스
• /
• 제1권3호
• /
• pp.35-44
• /
• 1997

The purpose of this study is to the processes and quality of local women's apparel production using the stretch fabric and to address the problems related to production in order to provide useful data for producing competitive apparels. The result of the survey can be summarized as follows; 1. Results of surveying the process for raw materials and notions indicated that most of the workers were ignorant of the properties of stretch fabrics. And most factories were stacking the stretch fabrics across improperly, while being aware of the properties of the fabrics through their experiences or in-company test. 2. The major problem involving spreading fabrics was the uneven tension, followed by static electricity, overlap and warp twist. The problems involving the cutting work were melting of the fabric by cutter and difference of size between upper and lower parts. 3. Most of the businesses were not tempering the fabric before and after its linking works due to lack of working space, short delivery time, ignorance and etc. The majority of the sample businesses were operating their cutters at the speed of 3,000 rpm or higher, which suggests a poor technological guidance.

• 대한기계학회논문집A
• /
• 제20권8호
• /
• pp.2508-2515
• /
• 1996

Determination of an optimal feed rate is valuable in the sense of the precision and efficient machining. In this regard, a new surface roughness model for the face milling operation that considered the radial and axal runouts of the inserts in the cutter body was developed. The validity of the model was proved through the cutting experiments, and the model is able to predict the real machined surface roughness exactly with the information of the insert runouts and the cutting conditions. From the estimated surface roughness value, the maximum feed rate that obtains a maximum naterial removal rate under the given surface roughness constraint can be selected by using a bisection method. Therefore, this mehod for optimizing the feed rate can be well applied to the using a bisection method. Therefore, this method for optimizing the feed rate can be well applied to the using selsction of the cutting condition during the NC data generation in CAM.