• 한국정밀공학회지
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• 제16권2호통권95호
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• pp.123-129
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• 1999

Ball-end milling process is widely used in the die and mold manufacturing because of suitable one for the machining of free-form surface. During the process, the pencil cutting operation can be adopted before finish cut to eliminate overload in uncut area caused by large diameter of ball-end mill. The ball-end mill cutter for the pencil cutting is easily deflected by cutting force due to the long and thin shape, and the tool deflection in pencil cutting is one of the main reason of the machining errors in a free-form surface. The purpose of this study is to find the characteristics of deflected cutter trajectory by constructing measurement system with eddy-current sensor. It was found that the severe reduction of corner radius produced the overcut during the plane cutting. Up cutting method induced the overcut both plane and slope cutting, but down cutting one induced the undercut. From the experiments, down cutting with upward cutting path can generate the small undercut surface.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 학술대회 논문집 전문대학교육위원
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• pp.112-116
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• 2007

If any of the set parameters such as the environment temperature, mold temperature are not maintained at a consistent level, the fail rate of injection molding products is increased. The price of the injection molding machine is very high, so in order to maximize the utilization of the machine that is required the production of a number of different products with minimum fail rate using a single machine. To prevent the defect products by an inspection process with perfect quality is very important to minimizing production of defect products in the molding process. Vision inspection systems are widely utilized in various manufacturing industries for quality assurance purposes. The vision inspection system consists of CCD camera and lighting system to capture the image of the subject of inspection, an image comparison algorithm using to determine the pass/fail of the products, and mechanical devices for the operation of the whole system. This research focuses on the development of the vision inspection system to process the inspection of an automobile parts. We developed a mechanical devices for the inspection of the injection molding products and an image comparison algorithm to determine the pass/fail result of the inspection based on the molding image and the accepted product image.

• 한국주조공학회지
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• 제32권2호
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• pp.65-74
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• 2012

In this paper, we present the results of our studies on optimal die design towards development of a vacuum die casting process to fabricate fuel cell bipolar plate with micro-channel array. Cavity and overflow shape is designed by computational filling analysis of MAGMA soft. Optimal die design consists of seven overflows at the end of cavity and three overflows at each side wall of cavity. The molten metal that passed the gate and reached the side wall flowed into the side overflow, no turbulent flow occurred, and the filling behavior and velocity distribution were uniform. In addition, partially solidified molten metal passing through the channel was perfectly eliminated by overflow without back-flow. When vacuum pressure, injection speed of low and high region was 300 mbar, 0.3 m/s and 2.5 m/s respectively with Silafont 36 die casting alloy, sound sample without casting defects was obtained. The experimental results are nearly consistent with simulation results.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제30회 춘계학술대회논문집
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• pp.203-206
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• 2008

본 연구는 고체 추진기관에 적용되는 내열재를 autoclave 방식이 아닌 hot press molding으로 제작하여 연소관에 접착 가능한 상태의 내열재로 제작하는데 초점을 두고 있다. EPDM/kevlar를 기본 조성으로 내열재 원료가 구성되고, 미가류 sheet 상태로 공급된다. 전방 내열재는 금형을 사용하여 preform 상태로 1차 제작하고, boots를 구형하기 위해 두개의 preform 사이에 modified nylon film을 사용하여 제작 하였다. 실린더 부위를 포함하고 있는 후방 내열재는 특별히 설계된 하나의 금형으로 제작되었고, boots 부위는 초경합금 칼날을 가지고 있는 장비에 의해 실현되었다.

• Nuclear Engineering and Technology
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• 제52권8호
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• pp.1714-1723
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• 2020

This study aims at characterizing the rheological properties of uranium oxide powders for nuclear fuel pellets manufacturing. The flowability of these powders must be compatible with a reproducible filling of press molds. The particle size distribution is known to have an impact on the rheological properties and fine particles (<100 ㎛) are suspected to have a detrimental effect. In this study, the impact of the particle size distribution on the rheological properties of UO₂ powders was quantified, focusing on the influence of fine particles. Two complementary approaches were used. The first approach involved characterizing the powder in a static state: density, compressibility and shear test measurements were used to understand the behavior of the powder when it is transitioned from a static to a dynamic state (i.e., incipient flow conditions). The second approach involved characterizing the behavior of the powder in a dynamic state. Two zones, corresponding to two characteristic behaviors, were demonstrated for both types of measurements. The obtained results showed the amount of fines should be kept below 10 % wt to ensure a robust mold filling operation (i.e., constant mass and production rate).

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2001년도 춘계학술대회 논문집(한국공작기계학회)
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• pp.422-428
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• 2001

The term High Speed Machining has been used for many years to describe end milling with small diameter tools at high rotational speeds, typically 10,000 - 100,000 rpm. The process was applied in the aerospace industry for the machining of light alloys, notably aluminium. In recent year, however, the mold and die industry has begun to use the technology for the production of components, including those manufactured from hardened tool steels. With increasing cutting speed used in modern machining operation, the thermal aspects of cutting become more and more important. It not only directly influences in rate of tool wear, but also will affect machining precision recognized as thermal expansion and the roughness of the surface finish. Hence, one needs to accurately evaluate the rate of cutting heat generation and temperature distributions on the machining surface. To overcome the heat generation, we used to cutting fluid. Cutting fluid play a roles in metal cutting process. Mechanically coupled effectiveness of cutting fluids affect to friction coefficient at tool-work-piece interface and cutting temperature and chip control, surface finish, tool wear and form accuracy. Through this study, we examined the behavior of heat generation in high-speed machining and the cooling performance of various cooling methods.

• Journal of Mechanical Science and Technology
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• 제19권2호
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• pp.496-504
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• 2005

The thermal and mechanical properties of an electro-slag cast steel of a similar chemical composition with an AISI-6F2 steel are investigated and compared with a forged AISI-6F2 steel. AISI-6F2 is a hot-working tool steel. Electro-slag casting (ESC) is a method of producing ingots in a water-cooled metal mold by the heat generated in an electrically conductive slag when current passes through a consumable electrode. The ESC method provides the possibility of producing material for the high quality hot-working tools and ingots directly into a desirable shape. In the present study, the thermal and mechanical properties of yield strength, tensile strength, hardness, impact toughness, wear resistance, thermal fatigue resistance, and thermal shock resistance for electro-slag cast and forged steel are experimentally measured for both annealed and quenched and tempered heat treatment conditions. It has been found that the electro-slag cast steel has comparable thermal and mechanical properties to the forged steel.

• 한국정밀공학회지
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• 제21권10호
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• pp.34-41
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• 2004

A new method to fabricate the fine magnetic abrasives by using mechanical alloying is proposed. The mechanical alloying process is a solid powder process where the powder particles are subjected to high energetic impact by the balls in a vial. As the powder particles in the vial are continuously impacted by the balls, cold welding between particles and fracturing of the particles take place repeatedly during the ball milling process using a planetary mill. After the manufacturing process, fine magnetic abrasives which the guest abrasive particles c lung to the base metal matrix without bonding material can be obtained. The shape of the newly fabricated fine magnetic abrasives was investigated using SEM and its polishing performance was verified by experiment. It is very helpful to finishing the injection mold steel in final polishing stage. The areal ms surface roughness of the workpiece after several polishing processes has decreased to a few nanometer scales.

• 한국공작기계학회논문집
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• 제16권5호
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• pp.77-83
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• 2007

The study on damaged layer is necessary for machinability improvement in micro machining. The damaged layer in metal cutting is derived from plastic deformation and transformation of metal structure. The damaged layer affects micro mold life and micro machine parts. In this study, the damaged layer of micro machined surface of copper is evaluated according to various machining condition. The damaged layer structure and metallurgical characteristics are measured by optical microscope, and evaluated by cutting forces and surface roughness. The scale of this damaged layer depends on cutting process parameters and machining environments. By experimental results, depth of damaged layer was increased with increasing of cutting depth, also the damaged layer is less occurred in down-milling compared to up-milling during micro endmilling operation.

• International Journal of CAD/CAM
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• 제12권1호
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• pp.20-28
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• 2012

Finite Element Analysis (FEA) is often used to identify local stress/strain concentrations where a component is likely to fail. In order to reduce the degree of strain concentration, component thickness can be increased in those regions, or a stronger material can be used. In short fiber reinforced composite materials, strength and stiffness can be increased through proper fiber alignment. The field-aided microtailoring (FAiMTa) process is one promising method for doing this. FAiMTa uses principles of dielectrophoresis to preferentially align particles or fibers within a matrix. To achieve the preferred fiber orientation, an interdigitated electrode network must be integrated into the mold halves which can be fabricated by additive manufacturing (AM) processes. However, the process of determining the preferred fiber arrangements and electrode locations can be very challenging. This paper presents algorithms to semi-automate the interdigitated electrode design process. The algorithm has been implemented in the Solidworks CAD system and is demonstrated in this paper.