• Transactions of Materials Processing
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• v.31 no.2
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• pp.96-102
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• 2022

The multi-point dieless forming technology is one of flexible forming technologies that can form 3D curved surfaces of various shapes utilizing a lot of punch arrangements. A new technology that can simultaneously apply high-temperature forming and flexible forming technology by fusing local heating effect to such multi-point dieless forming technology was proposed in the present study. A simple local heating multi-point dieless forming apparatus was fabricated to confirm the applicability of this new technology. This equipment was designed to be used as a heat source by inserting heating cartridges in the head of the multi-point punch. Cartridges were used for all individual punches. Using the manufactured equipment, the time to raise the temperature to the target temperature and the surface temperature of the punch head part in contact with the plate were measured. In addition, forming experiments were carried out according to sheet material temperature (100 ℃, 200 ℃, and 300 ℃) to obtain forming results for each condition. The applicability and feasibility of this technology were confirmed through experimental results.

• Transactions of Materials Processing
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• v.13 no.2
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• pp.129-136
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• 2004

Recently, instead of a matched die forming method requiring a high cost and long delivery term, a multi-point dieless forming method using a pair of matrix type punch array as flexible dies has been developed. Since the conventional multi-point dieless forming method has some disadvantages of difficulty in precise punch control and high-cost of equipment, a new concept of multi-point dieless forming method combined with an elasto-forming method has been suggested in this study. For optimal selection of elastomers, compression tests of rubbers, polyethylene and foams were carried out together with FEM analysis of the deformation behavior during sheet forming process using a rigid punch and elastomers. Compressive strain was concentrated on the upper central area of the elastomer under the punch, and the rubber exhibited higher concentration of the compressive strain than foams. Two-dimensional curved surface was formed successfully by the multi-point elasto-dieless forming method using an optimal combination of rubber and foam materials.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.08a
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• pp.21-28
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• 2003

Recently, instead of a matched die forming method requiring a high cost and long deliverly ten a multi-point dieless forming method using a pair of matrix type punch array as flexible dies has been developed. As this multi-point dieless forming method has some disadvantage of difficulty in precise punch control and high-cost of equipment, a new concept of multi-point dieless forming method combined with elastomer forming was suggested in this study. For optimal selection of elastomers, compression tests of rubbers, polyethylene and foams were carried out together with FEM analysis of the deformation behavior during sheet forming process using a rigid punch and elastomers. Compressive strain was concentrated on the upper central area of the elastomer under the punch, and the rubber exhibited higher concentration of the compressive strain than foams. Two-dimensional curved surface was formed successfully by the multi-point elasto-dieless forming method using an optimal combination of a rubber and foam.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.05a
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• pp.58-61
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• 2002

A new concept of dieless sheet forming technology is proposed in this study to overcome the drawback of conventional dieless forming technology. For this purpose, dual points contact of the conventional punch system, which is a primary cause of surface defects, is replaced to single point contact using technology combined with fluid forming. It is expected that the advanced system may lead to easy displacement control of multi-punch elements, reducing surface defects, and increasing decision and forming limits. The reduced number of punch elements also saves the cost of the equipment. In addition, the new technology can be utilized for deep drawing as well as two- or three-dimensional curved surface forming, and thereby become multi-functional and multi-purpose differently from the conventional technology.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.66-69
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• 2004

A new concept of multi-point dieless elasto-forming method has been developed to make various shape of curved surface without conventional dies. The developed dieless elasto-forming system consists of discrete punches controlled by servo motors and various kinds of elastomers(rubber and foam). To predict optimal position of punch elements, DTF(deformation transfer function) was introduced, and FEM analysis was carried out. The optimal arrangement of elastomer was selected considering characteristics of each elastomer, and a desired concave shape was formed. The experimental results were consistent with the numerical ones.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.152-155
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• 2005

A method of three-dimensional curved surface generation was studied for multi-point dieless forming (MPDF) in the shipbuilding industry. Three-dimensional coordinates of punch elements were obtained from objective surfaces using a proprietary CAD program. MPDF surfaces were generated by adjusting the height of punch elements in accordance with the coordinates. Some problems, such as collision of punch elements and contact between plates and punch bodies, were anticipated from the analysis of the results. A twisted surface was formed successfully by MPDF in a laboratory scale, which suggests possibility of application of the technology to the shipbuilding industry.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.220-223
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• 2008

Large curved plate blocks are widely used to construct hull structure in shipbuilding industry. Most curved plates are manufactured by using manual method called as line heating that use deformation caused by residual stress after local heating along a line which is perpendicular to the curvature direction. However, its working environment is poor and its formability is totally dependent on an experienced technician. In view of that, multi-point dieless forming (MDF) technology that use reconfigurable punch arrays instead of one piece die is proposed in this study. The MDF process is based on a concept of equivalent die surface made by numbers of punches which has round tip at the end of it. In this study, numerical simulation for common curvature type such as saddle shape was carried out. In addition, experiments in the plate forming process were also conducted to compare with the numerical results in view of final configuration. Consequently, it was noted that the proposed dieless forming method has considerable feasibility to substitute the new process for conventional manual method.

• 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.25 no.1
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• pp.12-20
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• 2016

Press machines and dies are commonly used for 3D curved sheet forming. Using conventional die forming can cause economic problems since various modifications of the die shape are required depending on the product shape. Various types of flexible forming such as multi-point dieless forming (MDF), flexible incremental roll forming have been developed to improve the needed process flexibility. Although MDF can reduce the production cost using reconfigurable dies, it still has significant material loss. Drawbacks such as wrinkling, dimpling, and forming errors can also occur despite continuous investigations to mitigate these defects. A novel sheet forming process for 3D curved surfaces, a flexibly-reconfigurable roll forming (FRRF), has been recently proposed to overcome the economic and technical limitations of current practice. FRRF has no limitation on blank size in the longitudinal direction, and also minimizes or eliminates forming defects such as wrinkling and dimpling. Feasibility studies of FRRF have been conducted using FE simulations for multi-curved shapes and various sheet thicknesses. Therefore, the fabrication of a FRRF apparatus is required for any follow-up studies. In the current study, experiments with reconfigurable rollers were conducted using a simple design pre-FRRF apparatus prior to fabricating the full size FRRF apparatus. There are three candidates for the reconfigurable roller: a bar-type shaft, a flexible shaft, a ground flexible shaft. Among these candidates, the suitable reconfigurable roller for FRRF is determined through various forming tests.