• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.5
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• pp.512-518
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• 2014

In this paper, the influence of part shape complexity and die type on forming accuracy in incremental sheet metal forming is presented. The part shape complexities are classified into two types, namely, of one and two-step shapes. Correspondingly, die types are classified into three types, namely, of no-, partial, and full die types. The experimental tests are performed separately on negative and positive forming methods. It is shown that for the one-step shape, there are no significant differences in forming errors between the cases of no- and full die types when the negative forming method is used. Furthermore, the full die type is better than the partial die when positive forming is used. For the two-step shape case, the full die type always exhibits better forming accuracy than the no- and partial die types, irrespective of the forming method used.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.118-121
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• 2008

Flexible die is more efficacious than fixed die which is generally used in stretch forming process in view of production cost. Accordingly, in order to verily the validity of the flexible forming process, curved thin skin structure forming analyses using the fixed and flexible die were performed. As results, merit and demerit with regard to the fixed and flexible die were confirmed. The result of the stretch forming process analysis using the flexible die was better than that using the fixed die in view of the elastic recovery. However wrinkles were occurred on the sheet material due to die cavities between the punches in the flexible forming process, thus the solutions against these problems were presented.

• Transactions of Materials Processing
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• v.11 no.3
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• pp.223-230
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• 2002

Matched die forming technology has been used widely as a sheet metal forming method for a long time. This conventional method, however, needs a high cost and long delivery time to prepare a set of matched dies or, in many cases, several sets of dies. For more than ten years, some alternative methods using single die or non-matched dies have been developed and applied practically in various fields of industry. Elasto-forming, fluid forming, hydro-forming, and blow forming are some examples of these new methods. Recently, a dieless sheet forming technology using a reconfigurable matrix of punch elements has been developed, and started to be used in some industries such as aircraft and railroads. A new concept of dieless forming technology has also been proposed to overcome the drawback of the conventional dieless forming technology.

• Transactions of Materials Processing
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• v.18 no.7
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• pp.556-564
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• 2009

Flexible forming process for sheet material using reconfigurable die is introduced based on numerical simulation. In general, this flexible forming process using the reconfigurable die has been utilized for manufacturing of curved thick plates used for hull structures, architectural structures and so on. In this study, numerical simulation of sheet metal forming process is carried out by using flexible dies model instead of conventional matched die set. The numerical simulation and experimental verification for sheet metal forming process using a flexible forming machine that is more suitable for thick plate forming process are carried out to confirm the appropriateness of the simulation process. As an elastic cushion, urethane pads are utilized using hyperelastic material model in the simulation for smoothing the forming surface which is discrete due to characteristics of the flexile die. In the flexible forming process for sheet metal, effect of a blank holder is also investigated according to blank holding methods. Formability in view of occurrence of dimples is compared with regard to the various punch sizes. Consequently, it is confirmed that the flexible forming for sheet material using urethane pad has enough capability and feasibility for manufacturing of smoothly curved surface instead of conventional die forming method.

• Transactions of Materials Processing
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• v.17 no.8
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• pp.570-578
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• 2008

A flexible forming apparatus is composed a number of punches which have spherical pin tip shape instead of conventional solid die. The flexible forming tool consisted of punch array in a matrix form was proposed as an alternative forming method to substitute the conventional line heating method which use heat source to induce residual stress along specified heating lines. In this study, application of the flexible forming process to the small scale curved plate forming was conducted. Numerical simulations for both solid and flexible die forming process were carried out to compare the shape of the products between flexible and conventional die forming process. In addition, spring-back analysis was conducted to figure out the feasibility of the flexible forming process comparing with the die forming process in view of final configuration of the specimens. Moreover, experiment was also carried out to confirm the formability of the process. Consequently, it was confirmed that the flexible die forming method has capability and feasibility to manufacture the curved plates for shipbuilding.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.143-147
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• 2003

Despite of outstanding optical performance of glass lens, glass lens have not been widely used because of poor productivity and high cost due to manufacturing process i.e. grinding, polishing. However, press-forming method of glass lens overcomes this disadvantage because of mass production. When glass lens is produced by press-forming method using closed die, it is needed that the volume of glass lens preform precisely measured in order to prevent incomplete products and to increase in life of die. The present paper shows the shortcoming of forming process with closed die, and performs FEM simulation of forming process with open die in order to overcome this shortcoming. The design parameter of open die is selected in standard of assembly with optical module and maintenance of optical performance. FEM simulation is carried out with selected parameter of open die and two basic preform. According to distribution of effective strain in glass lens, optical property of glass lens formed at each set of die and preform is compared.

• Transactions of Materials Processing
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• v.12 no.4
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• pp.296-301
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• 2003

Though a glass tens has outstanding optical performance, it has not been widely used because manufacturing process shows poor productivity and high cost. However, press-forming method of glass lens overcomes these disadvantages with mass production. When glass lens is produced by press-forming method using closed die, it is needed that the volume of glass lens preform is precisely measured in order to prevent incomplete products and to increase in life of die. The present. paper shows the shortcoming of forming process with closed die, and performs FEM simulation of forming process with open die in order to overcome this shortcoming. The design parameters of open die are selected on the basis of assembly with optical module and maintenance of optical performance. FEM simulation is carried out with selected parameter of open die and two basic preform. According to distribution of effective strain in glass lens, optical property of glass lens formed at each set of die and preform is compared.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.4
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• pp.712-720
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• 1988

This paper describes some development of computer-aided system called "COLD-FORMING" and "DESIGN-DIE". "COLD-FORMING" is designed for the forming sequence and "DESIGN-DIE" for the die design of press forming rotationally symmetric parts. The computer program developed is used in interactive and written in BASIC. Design rules for process planning and die design are formulated from process limitations, plasticity theory and know-how of experience of the field. "COLD-FORMING" capabilities include (1) analysis of forming sequence and recognition of individual operation involved each step, (2) determination of intermediate shape and dimensions, (3) calculation of forming loads to perform each forming operation and (4) graphic out put for the operation sheet. "DESIGN-DIE" capabilities include (1) optimum die design corresponding to the output of "COLD-FORMING" and (2) graphic output for the die design.of "COLD-FORMING" and (2) graphic output for the die design.ie design.

• Transactions of Materials Processing
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• v.15 no.5 s.86
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• pp.387-394
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• 2006

In order to see the effect of die deformation on the forming analysis of sheet metals, the draw-ins, strains, and spring-backs of an automotive fender panels are numerically simulated by considering the die deformation found by the simultaneous structural analysis of press and dies. By coupling the forming analysis and the structural analysis, the die deformation is simultaneously taken into account in the forming process. Furthermore, for the consideration of load difference transferred among the upper die, punch, and blank holder due to the changes in sheet thickness, the gap elements are employed instead of the blank sheet in the structural analysis. The numerical simulation results of an automotive finder draw panel are compared with the measurements. The comparison of the forming and spring-back analysis results between the rigid die and the deformed die shows that the consideration of tool deformation can predict more accurately the forming and spring-back of sheet metals.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.1
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• pp.167-174
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• 2012

For high production rate of parts requiring multiple operations such as punching, blanking, or other operations are generally done with progressive dies. However, progressive die is generally limited to use for sheet metal forming due to the technical difficulties in rod or bulk material. This study proposes a new technique of progressive die and forming process for asymmetric automotive door striker, which is conventionally manufactured with separate tandem processes using solid rod. In order to design forming process and die, FEM simulation was performed to divide proper intermediate processes and analyze its formability. As a result, Forming processes were divided into 3 stages with upper and side punches and also, workpiece feeding and location mechanism was designed and manufactured in this study. Finally, forming tryouts were carried out by using the manufactured progressive die to verify the forming quality and productivity.