• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1995년도 추계학술대회 논문집
• /
• pp.232-235
• /
• 1995

A side-extrusion model, meant for deeper understanding of the material flow in the CONFORM (continuous extrusion forming) of trub shaped aluminum profiles is presented. In order to get the desirded straight shape of the extrudate,every part of its cross-section must exit the die with the same velocity. Problem is assumed by plane strain UBET-model to analyze it in a simplified way. This has been done by studying the side-extrusion through a two -hole die face. The flow is balanced by determining the optimum lengths of the bearing lands, i.e., those lengths which result in equal exit velocities of the extrudates. Furthermore, the material flow, as influenced by the punch velocity, has been investigated.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2000년도 추계학술대회 논문집
• /
• pp.78-81
• /
• 2000

In this study the plasic flow before welding stage in the cahamber is analyzed by FEM and experiments during the porthole extrusion process. The analysis is concerned with plastic flow in the port and welding chamber of rectangular hollow section extrusion through the porthole die with mandrell. Numerical simulation by finite element code to investigate the plastic flow is discussed for both tapered inlet and straight inlet chamber. To visualize the flow in extrusion process split dies and punches are designed and manufactred by wire EDM. Experiments are carried out by using the plasticine as a model material at room temperature. The theoretical predictions are reasonable agreements with experimental results in the welding lines and the deformed profiles.

• 한국정밀공학회지
• /
• 제11권4호
• /
• pp.26-37
• /
• 1994

A kinematically admissible velocity field for the numerical analysis of closed-die forging process of spur gear is proposed. The velocity field is divided into three regions of deformation. In the analysis, the involute curve is approximated to be straight line and the upper-bound method is used to calculate energy dissipation rate. A constant frictional frictional factor has been assumed on the contacting surfaces. The effects of root diameter, number of teeth, and friction factor are determined on the relative forging pressure. The frictionless relative pressure is independent of root diameter for the same number of teeth, but increases with the number of teeth on a given root diameter. In the presence of friction, the relative forging presure increasing root diameter at the start of forging, but decreases with increasing root diameter in the processing of forging.

• 한국정밀공학회지
• /
• 제15권2호
• /
• pp.90-98
• /
• 1998

Forging of internal involute gears with alloy steel has been analyzed by means of upper bound method. Kinematically admissible velocity fields for forging of internal gear were proposed. It was assumed that the shape of free flow surface during forging operation is a straight line perpendicular to the plane of symmetry. Using the suggested velocity fields, forging loads and relative pressures were calculated by numerical method. Consequently forging die should be successfully designed without fracture or failure during forging operation. Experiments were carried out with the designed die and SCM415 alloy steel as billet material. The calculated loads were compared with experimental one and they are in good agreement with experimental inspections. As a result, the calculated solutions would be useful to predict the loads and the designed die is suitable for forging of internal involute spur gear with alloy steel. The forged gear is measured to be KS 4 class and its class should be improved by subsequent working such as shaving after forging operation.

• 대한기계학회논문집A
• /
• 제35권12호
• /
• pp.1647-1653
• /
• 2011

일반적으로 사출금형의 사출주기는 플라스틱 제품의 냉각 시간에 크게 좌우되는 데, 냉각회로를 적용하여 조절할 수 있다. 금형의 냉각회로는 전통적으로 기계가공을 통하여, 직선형상만을 생성할 수 있었지만, 최근 적층조형 방법의 개발로 코어 형상을 따라가는 형상적응형 냉각회로를 생성할 수 있게 되었다. 한편 금형의 다이 재질로 열저항력이 크고, 치수변화가 적은 H13 스틸이 널리 사용되고 있지만, 열전도율이 낮기 때문에 냉각효율은 높지 않다. 이러한 점에서 열전달 효율을 극대화 시킬 수 있는 방법으로 H13 스틸과 구리(Cu)를 기능적으로 혼합한 기능성 경사 복합재(FGM)를 적층조형을 이용하여 냉각회로에 적용하는 방안이 검토되고 있다. 이러한 시도로서 본 논문에서는 H13 스틸과 Cu 간의 FGM을 이용한 형상적응형 냉각회로의 모델링 방법을 제안하고자 한다.

• 한국공작기계학회논문집
• /
• 제13권6호
• /
• pp.87-93
• /
• 2004

An experimental is carried out to investigate the characteristics of blanking for nickel alloy Alloy42 (t=0.203mm), a kind of IC lead frame material. By varying clearance between die and punch the shapes of shear profile are examined. Finite element analysis with element deletion algorithm for ductile fracture mode is also carried out to study the effect of clearance theoretically and to compare with experimental results. The rectangular shape specimen with four different comer radius is used to study the characteristics of blanking for straight side and comer region simultaneously. As the result the ratios measured k(m experiment of roll over, burnish and fracture zone based on initial blank thickness are compared with those of FE analysis. Both experiment and FE analysis show that the amount of mil over and fracture is increased as the clearance increases. When the radius of comer is less than thickness of blank it has been found that larger clearance is required than that of straight region in order to maintain same quality of shear profile at the comer region.

• Design & Manufacturing
• /
• 제1권1호
• /
• pp.27-32
• /
• 2007

In the optical application demand for high quality lens is increasing. Plastics lenses are demanded more than glass lenses for large size lenses as well as micro-size lenses. It is difficult to apply typical straight cooling channels of injection mold to lens molding due to its non-uniform temperature distribution. In this study, we manufactured molds for plastic lenses with the conventional cooling channels and conformal cooling channels produced by the DMLS process. We evaluated cooling performance for the 2 molds by injection molding experiment. Also, uniformity of the temperature distribution was tested by infrared camera and temperature monitoring. We confirmed that the cooling performance and temperature uniformity with the conformal cooling channels is much improved from the ones with the conventional. The cooling time with the conformal cooling channels was reduced 30% compared with the conventional cooling channels.

• 대한치과보철학회지
• /
• 제36권5호
• /
• pp.738-747
• /
• 1998

The purpose of this study was to compare the positional stability of removable dies using several dowel pin systems. The removable dies were made by using five dowel pin systems: single dowel pin(Group I), single dowel pin and prepared groove on the die base(Group II), two-single dowel pin(Group III), two separate parallel dowel pins with plastic sleeves(Group IV), double straight dowel pins with metal sleeve(Group V). Special aluminum mold was made for specimens, and the dies of specimens removed and replaced thirty times with universal testing machine. Horizontal and vertical shift of dies was measured by Olympus monocular scanning tunneling microscope(STM5). The results were as follows: 1. The vertical shift was larger than the horizontal shift in all the other groups except Group I. 2. Single dowel pin system(Group I) was the most unstable of five dowel pin systems. 3. Double dowel pin systems with steeve(group IV, V) were the most stable of five dowel pin systems. 4. This study indicates that excellent horizontal positional stability is attainable with use of additional groove on the die base or double dowel pin. and excellent vertical positional stability is attainable with use of sleeve.

• 한국기계가공학회지
• /
• 제18권6호
• /
• pp.33-38
• /
• 2019

Researchers have recently begun to study hot stamping processes to shorten the mold cooling time and improve productivity. These publications explain that the mold cooling time can be reduced by using a curved cooling channel, where the mold surface is processed to a uniform depth, instead of a straight cooling channel that uses the conventional gun drilling machine. This study investigates the characteristics of the front pillar of an automobile after using a mold with a curved cooling channel. To analyze the change in properties, we used a 1.6 mm boron steel blank and heated the prototype at $930^{\circ}C$ for 5 minutes. Next, we formed the prototype with a load of about 500 tons while varying the mold cooling time between 1 and 10 seconds. We subjected each prototype specimen to a tensile strength test, a hardness test, and a tissue surface observation.

• 소성∙가공
• /
• 제15권6호
• /
• pp.428-435
• /
• 2006

IC leadframe needs precision shape for good efficiency. Friction conditions also have a significant impact on blanking deformation. Therefore, studying the friction produced by the tribology between die and materials becomes necessary. In this study, in order to measure mechanical properties and frictions for leadframe materials such as Ni alloys and coppers, tensile test and straight pulling friction test are executed. In particular, the effect of clearance on the blanking characteristics depending on friction coefficient is examined by finite element simulation. From the finite element simulation, the metal flow, side pressure of punch and crack initiation are evaluated according to the leadframe materials.