• 소성∙가공
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• 제12권1호
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• pp.18-25
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• 2003

This paper explains the process design for improving tool life in the conventional hot forging process. The thermal load and the thermal softening are happened by contact between the hotter billet and the cooler tools in hot forging process. Tool life decreases considerably due to the softening of the surface layer of a tool was caused by a high thermal load and long contact time between the tools and the billet. Also, tool life is to a large extent limited by wear, heat crack and plastic deformation in hot forging process. Above all, the main factors which affect die accuracy and tool life we wear and the plastic deformation of a tool. The newly developed techniques for predicting tool life are applied to estimate the production quantity for a spindle component and these techniques can be applied to improve the tool life in hot forging process.

• 한국정밀공학회지
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• 제23권7호
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• pp.177-186
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• 2006

In order to realize a three-dimensional shape on CAD, the machining process has been widely used because it offers practical advantages such as precision and versatility. However, the traditional machining process needs a large amount of time in cutting a product and the remained material causes trouble such as inconvenience due to cleaning process. Therefore, a new rapid manufacturing process, Rapid Heat Ablation process (RHA) using the hot tool, has been developed. In this paper, the hot tool for RHA process is designed to minimize radius of heat affected zone. TRIZ well-known as creative problem solving method is applied to overcome the contradictive requirements of the hot tool. For the detailed design of the hot tool, numerical model is established with several assumptions. In order to verify the numerical results, surface temperature of the hot tool is measured with K-type thermocouple at the predetermined location. Numerical and experimental results show that the devised hot tool fulfils its requirements. The practicality and effectiveness of the designed hot tool have been verified through experiments.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.743-748
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• 2005

In order to realize a three-dimensional shape on CAD, the machining process has been widely used because it offers practical advantages such as precision and versatility. However, the traditional machining process needs a large amount of time in cutting a product and the remained material causes trouble such as inconvenience for clarity. Therefore, a new rapid manufacturing process using the hot tool, Rapid Heat Ablation process (RHA), has been developed. In this paper, the hot tool for RHA process is devised to minimize radius of heat affected zone and also investigated for verification. TRIZ well-known as creative problem solving method is applied to overcome the contradictive requirements of the hot tool. For the detailed design of the hot tool, numerical model is established with several assumptions. Based on the numerical results, surface temperature is measured with K-type thermocouple at the predetermined location. Numerical and experimental results show that the devised hot tool fulfils its requirements. It verifies the practicality of hot tool that the hemisphere shape is ablated using the hot tool with stair structure.

• 한국정밀공학회지
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• 제31권12호
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• pp.1093-1100
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• 2014

The goal of this paper is to investigate preliminary the applicability of 3D printing technologies for the development of the hot bulk forming process and die. 3D printing technology based on the plastic material was applied to the preform design of the hot forging process. Plastic hot forging dies were fabricated by Polyjet process for the physical simulation of the workpiece deformation. The feasibility of application of Laser-aided Direct Metal Rapid Tooling (DMT) process to the fabrication of the hot bulk metal forming die was investigated. The SKD61 hot-working tool steel was deposited on the heat treated SKD61 using the DMT process. Fundamental characteristics of SKD 61 hot-working tool steel deposited specimen were examined via hardness and wear experiments as well as the observation of the morphology. Using the results of the examination of fundamental characteristics, the applicability of the DMT process to manufacture hot bulk forming die was discussed.

• 한국CDE학회논문집
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• 제9권4호
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• pp.286-293
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• 2004

Recently, hot processing using the heat source like laser machining and RFS was developed and spreaded gradually. In order to generate tool-path for the proper hot tool, a new tool-path linking algorithm is needed because tool-path linking algorithm for machining can't be applied. In this paper, zigzag tool-path liking algorithm was proposed to generate tool-path automatically for RFS. The algorithm is composed of three steps: 1) Generating valid tool-path element, 2) Storing tool-path elements and creating sub-groups, 3) linking sub-groups. Using the proposed algorithm, CAD/CAM software for the tool-path generation of hot tool was developed. The proposed algorithm was applied and verified for Venus's face and die of cellular phone case.

• Design & Manufacturing
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• 제6권1호
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• pp.39-44
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• 2012

Hot tool steel, in general, has not been used as a material in hot forging. However such a hot tool steel is recently applied to forging materials by recent forging technology. DH32 is known as a kind of hot tool steels, which is developed for characteristics of excellent strength and toughness in high temperature. Feasibility of DH32 to hot forging material has been researched to develop the hot forging technology of a plunger used for a large-sized marine fuel pump. Hot compression experimental works were performed to investigate the hot strain characteristic of DH32 and with the experimental results FE simulations were also conducted for the design of forging processes and preform. It is found out through the hot compression experimental works that DH32 has a hot brittleness at more than $1150^{\circ}C$.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 단조 심포지엄
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• pp.141-146
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• 1999

In the stage of process design, many factors affecting tool life should be considered. Wear, Damage Accumulation and excessive die Stress are those. Most Engineer think wear and damage accumulation affection deeply to the cold forging dies and wear for the hot forging dies. In this report, the example that wear and stress distribution affect tool life in hot forging together will be introduced and the way to solve that problem using Finite Element Method.

• 대한기계학회논문집B
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• 제30권10호
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• pp.957-965
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• 2006

A high-performance hot chuck is designed as a heating device for an ultra-precision flip-chip bonder with infrared alignment system. Analysis of design requirements for thermal performance leads to a radiative heating mechanism employing two halogen lamps as heating source. The heating tool is made of silicon carbide characterized by high thermal diffusivity and small thermal expansion coefficient. Experimental tests are performed to assess heat-up performance and temperature uniformity of the heating tool. It is revealed that the initial design of hot chuck results in a good heat-up speed but there exist a couple of troubles associated with control and integrity of the device. As a means to resolve the raised issues, a revised version of heating tool is proposed, which consists of a working plate made of silicon carbide and a supporting structure made of stainless steel. The advantages of this two-body heating tool are discussed and the improved features are verified experimentally.

• 한국정밀공학회지
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• 제28권1호
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• pp.63-72
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• 2011

In recent years, hot-stamped components are more increasingly used in the automotive industry in order to reduce weight and to improve the strength of vehicles. In hot stamping process, blank is hot formed and press hardened in a tool. However, in hot stamping without cooling channel, temperature of the tool increases gradually in mass production thus cannot meet the critical cooling rate to obtain high strength over 1500MPa. Warpage occurs in the hot stamped component due to non-uniform stress state caused by unbalanced cooling. Therefore, tools should be uniformly as well as rapidly cooled down by the coolant which flows through cooling channel. In this paper, optimal design method of cooling channel to obtain uniform and high strength of the component is proposed. Optimized cooling channel is applied to the hot press V-bending process. As a result of measuring strength, hardness and microstructure of the hot formed parts, it is known that the design methodology of cooling channel is effective to the hot stamping process.

• 한국자동차공학회논문집
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• 제15권4호
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• pp.47-53
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• 2007

A bearing is one of core parts in automobile. Rubber seal of the bearing is important to improve performance of bearing, formed by hot-press die of rubber seal for the intricate shape. In this study, formed tools are used to machine die of bearing rubber seal and the machining operation is classified into the several process of high precision. Design of experiments is used to optimize selection of the formed tools for the efficient machining of the hot-press die. The cutting force, tool wear and tool life are determined to characteristics. And, the clearance angle, the rake angle and the length cutting edge are considered as the major factors. Experiments are repeated to use one-way factorial design, and tool life is predicted by regression model.