• Journal of the Korean Society for Precision Engineering
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• v.7 no.2
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• pp.95-104
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• 1990

This paper descirbes some research of Computer-aided Design of multi-stage cold forging die of rotationally symmetric parts produced by the press or former. An approach to the system is based on knowledge based system. Knowledges for tool design are extracted from the plasticity theory, handbooks, relevent references and empirical know-how of experts in cold forging companies. The deveoped system is composed of three main modules such as die design module, punch design module, tool elements design module which are sued independently or in all. Using this system, design parameters (types of dies, geometric shapes and dimensions of dies, types of punches, geometric shapes and dimensions of punches, geometric shapes and dimensions of tool elements) in each operation are determined and the output is generated in graphic form. The develpoed system, aids designer, provides powerful capability for designing dies, punches and tool elements.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.87-90
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• 2004

In this paper, net-shape forming of an automobile gear is investigated. Barrel, a component of automobile start motor, is adopted as a net-shape forming. In order to accomplish the goal of net-shape forming without cutting of tooth and cam after forming, forming ability is raised through billet treatment and die design. As a technique of billet treatment spheroidizing annealing of billet to get low hardness and molybdenum disulphide coating to get low contact friction between billet and die is carried out. One of critical points of die design, fillet radii variation of tooth of die is applied to get smooth surface of barrel after cold forging. As a measurement of tooth accuracy, distance between two pins and lead-tooth alignments are investigated. Cam profile accuracy is checked with a 3D measuring instrument. Results obtained from the tests revealed reasonable result with respect to design goal. By these results, the paper shows that reasonable results can be obtained by billet treatment and die design for net-shape forming.

• Journal of the Korean Society of Industry Convergence
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• v.5 no.1
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• pp.11-19
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• 2002

This study described computer aided die design system for cold forging of non-axisymmetric parts such as gears and splines. To design the cold forging die, an integrated approach based on a rule-base system and commercial F. E. code were adopted. This system is implemented on the personal computer and its environment is a commercial CAD package named as Auto CAD. The system includes four modules. In the initial data input module, variables which are necessary to design of die are inputted by user and die material are selected from the database according to the variables. In the analysis and redesign module, stress distribution acting on the designed die is analyzed by commercial FEM code NISA II with elastic mode. If die failure predicted, the designed die would modified in four ways to prevent die failure in both states of stress free and pressurizing. The developed system provides useful date and powerful capabilities for die design of non-axisymmetric parts.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.10 s.181
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• pp.2610-2618
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• 2000

In this paper, the elastic deformation of cold forging die has been investigated to improve the accuracy of forged parts with FEM analysis and experiments using the strain gages. In the finite element analysis, two types of analysis are used to predict elastic deformation of die. The one is that dies are considered to be elastic body from initial stage to final one, and the other is that the dies are considered to be rigid body during forging simulation and then considered to be elastic body at elastic analysis. Considering the results of analysis and experiments, it is likely that the analytical results are in good agreement with experimental inspections. The method using the elastic assumption of die relatively takes a lot of time to simulate the forming operation. However, It is better that using an elastic die to predict not only the shape of product but also filling of die cavity.

• Transactions of Materials Processing
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• v.31 no.6
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• pp.376-383
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• 2022

The potential damage region of a WC-Co cemented carbide die is investigated for cold forging process of a wheel-nut by numerical simulation with its chemical composition considered. Numerical simulation is utilized to calculate internal stress, especially for the WC-Co die, during the forging process. Finite element model is established, in which the elasto-plastic properties are applied to the work-piece of bulk steel, and elastic properties are considered for the lower die insert of the WC-Co alloy. This stress analysis enables to distinguish the potential damage regions of the WC-Co die. The regions from calculation are comparatively analyzed along with the crack area observed in the die after repetitive manufacturing. Effect of chemical composition of the WC-Co is also evaluated on characteristics of potential damage region of the die with variance of mechanical properties considered. Derived from Mohr-Coulomb fracture model, furthermore, a new stress index is presented and used for die stress analysis. This index inherently considers hydrostatic pressure and is then capable of deducing wide range of its distribution for representing stress state by modification of its parameter implying pressure sensitivity.

• Transactions of Materials Processing
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• v.21 no.7
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• pp.397-402
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• 2012

The flange hub is a main component in an automotive steering system. In general, the flange hub are fabricated by mechanical machining, which is a process where material waste is inevitable. It is well-known that a net-shape cold forging cannot only reduce material waste but can also improve the mechanical strength of the final product. Thus, a forging process design was conducted for production of a flange hub. Significant spring-back occurs around the flange due to its small thickness in conjunction with the residual stresses after forging. In order to achieve the required dimensional accuracy, a process design with appropriate spring-back control is needed. In this study, a modification of the forging die was designed based on FE analysis with the purpose of spring-back compensation. Four kinds of different die designs were evaluated and the optimum design has two times less spring-back than the initial design. The compensation angle of the optimum design is 0.5 degrees. The results have been experimentally confirmed by cold forging of a flange hub and comparing the amount of spring-back between the actual component and the FE analysis.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.12
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• pp.8-15
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• 2021

Cold forging is a method in which molding is performed at room temperature. It has a high material recovery rate and dimensional precision and produces excellent surface quality, and it is mainly used for the production of bolted or housing products. The lifespan of cold forging molds is generally determined by the wear of the mold, plastic deformation of the mold, and fatigue strength. Cold forging molds are frequently damaged due to fatigue destruction rather than wear and plastic deformation in a high-temperature environment as it is molded at room temperature without preheating the raw material and mold. Based on the results analyzed through FEM, an effective mold structure design method was proposed by analyzing the changes in tensile and compressive stresses on molds according to the number of molds and reinforcement rings and comparing the product geometry and mold stress using three existing mold models.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.1
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• pp.190-198
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• 1989

Some Developments in computer aided procedures for cold forging process and tool design of rotationally symmetric cup shape parts are described. The developed system enables appropriate forging sequence to be determined automatically, together with details of corresponding preform, die and punch design. The computer program developed is interactive and written in BASIC. This system not only assist the heavy work of designers but greatly shorten the time of design.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.584-588
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• 1997

Lots of forginfs used in automobile and aerospce industries are made in hot or cold working conditions, depending on the size and shape of a product. Usually the die design for new items has been first made on the basis of experiences and many know-hows accumulated in the company and then slightly modified through trial and error method to get the desired forgings without defects. Most of drawings at the die design stage have been manually drawn, butrecently some of forging companies have begun to apply a computer-aided drafting technique to the die design for reducing drafting time as well as repeatedly utilizing standardized parts form registerd data base. In this paper the automated die design technique for forward extrusion of axisymmetric forgings is developed by using AutoLISP language. For this study the representative die system is determined form the investigation of several types of forging dies being currently employed in the metal forming field and the design rules for cold extrusion die are summarized and programmed on a personal computer. A few design examples of forward extrusion die are given and discusses.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.2
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• pp.295-303
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• 2009

Forging of square spline was investigated by using finite element methods in this study. Spline is widely used by torque transmitter in the fields of automobile, aircraft, and shipping etc. Friction on the surface of die is regarded as the most important factor to improve the dimensional accuracy for complete forming of spline teeth. Finite element simulation was carried out to improve the formability of the spline, especially remove unnecessary burrs which were extruded in gap between the die and the punch. To remove the burrs, various friction factors are considered on the surfaces of the die in the simulations and punch flat surface was designed. The simulated results were compared with experimental ones. As a results, it is possible to control the growth of burrs and improve formability of spline teeth by applying various friction factors and design of punch flat surface.