• Design & Manufacturing
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• 제2권1호
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• pp.1-5
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• 2008

Restriking method is to add to process in order to get the correct size and high precision accuracy of product which is formed in pre-process. This method is widely used at bending work and drawing work. Restriking die is particularly design and used as restriking process is performed. Therefore, production cost is increasing as one process or a two process are added. In this paper, punches and die block of square shell drawing die which could be performed drawing work and restriking process by using only one die are designed in order to solve these factors. The structure of sectional die which can integrate drawing die and restriking die was developed.

• Design & Manufacturing
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• 제2권1호
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• pp.7-10
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• 2008

Restriking method is to add to process in order to get the correct size and high precision accuracy of product which is formed in pre-process. This method is widely used at bending work and drawing work. Restriking die is particularly design and used as restriking process is performed. Therefore, production cost is increasing as one process or a two process are added. In this paper, punches and die block of square shell drawing die which could be performed drawing work and restriking process by using only one die are designed in order to solve these factors. The structure of sectional die which can integrate drawing die and restriking die was developed.

• 한국산학기술학회논문지
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• 제8권4호
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• pp.708-712
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• 2007

금형산업체에서 프레스금형의 성형 중에 적용하고 있는 리스트라이킹(Restriking)공법은 앞 공정에서 성형된 제품의 정확한 치수와 정밀도 높은 형상을 얻기 위하여 공정을 추가하는 것을 뜻한다. 이 공법은 벤딩가공(Bending work), 드로잉가공(Drawing work) 등에서 많이 사용되고 있다. 본 연구에서는 상기의 요인을 해소하기 위하여 1벌의 금형으로 드로잉 성형과 리스트라이킹을 할 수 있는 각종 드로잉금형의 펀치와 다이블록의 형상설계를 제시하고 이것에 대해 고찰하였다.

• Design & Manufacturing
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• 제12권3호
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• pp.31-35
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• 2018

In this paper, the method of improving the flatness and perpendicularity for a corner fixing bracket of the large display frame is studied through experiments. Three specimens were tested, one specimen not subjected to bending line before bending, and two specimens with a straight groove with 0.2 mm and 0.5 mm depth. Experimental results show that the flatness of bracket becomes worse with deeper depth. When there is no straight groove, the perpendicularity becomes worse. For the flatness correction, a restriking process was added. The twist of bracket was corrected by performing the restriking with a curvature larger than the twist amount in the direction opposite to the deformed direction. We also found that the perpendicularity is maintained regardless of the amount of curvature with the restriking process.

• Design & Manufacturing
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• 제8권1호
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• pp.5-9
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• 2014

This study is about 3D design for parts supporting copper pipes of wall-mounted air-conditioners manufactured by company "D" in Japan. Domestic press die manufacturers are obsessed with 2D die design and are afraid of taking risk with developing 3D die design and die manufacture. This hinders paradigm shift. In this study, the strip layout, which was already completed in the previous study, is altered by adding restriking. Based on the modified strip layout, the 3D die design is done in 15 processes.

• Design & Manufacturing
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• 제12권3호
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• pp.13-18
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• 2018

Flexible display tends to grow every year, It tends to be larger, slimmer, and higher in image quality. Therefore, accuracy is required in the manufacturing process of each part. In the curved monitor, the bottom chassis has a structure to which other parts can be attached. The accuracy of the curvature which the bottom chassis of the curve monitor monitors has is important. If the curvature error is large, serious defects such as cracks, warpage, twisting and the like occur. Curvature was analyzed using 3D scanner. In the Forming process and Restriking process steps, spring go occurred, and spring back occurred in the Notching process and Bending process steps. Even in the same process, it was confirmed that the curvature value varied depending on the formed shape.

• 한국공작기계학회논문집
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• 제16권5호
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• pp.166-171
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• 2007

In this paper Research development about a micro metal forming manufacturing system has been developed. A micro forming system has been achieved in Japan and it's developed micro press is limited to single forming process. To coincide with the purpose to be more practical, research and development is necessary about the press which the multi forming process is possible. We set the development of the equipment including micro deep drawing, micro punching and micro restriking process to the goal. To achieve this goal, we set the application product to a micro thin foil valve which is used in the micro pump module. The compound die set has been designed and manufactured to make two step process. The material of thin foil valve is SUS-304 and its thickness is 50$\mu$m. We can get a good forming results from micro punching experiments in this paper.

• Design & Manufacturing
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• 제12권1호
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• pp.52-57
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• 2018

With the recent strengthening of environmental regulations and the need for cost reduction, excavators, a type of construction equipment, are being miniaturized while components are being developed in consideration of stability. In the case of excavator press parts, mainly high-strength steel sheets are being used to enhance stability and reduce weight. However, in the case of high-strength materials, there is a need to research product forming methods to reduce Springback in defects arising in parts assembly due to Springback that result from the internal residual stress that occurs in press forming being released after product forming. Accordingly, regarding the tank cover, an excavator press-forming part, this study selected a method to reduce distortion through analysis of the Springback occurrence rate and Springback causes through a forming analysis. A forming analysis was conducted for the Springback of the tank cover. Deformations of 13.714 mm in the upper part and 6.244 mm in the inner part of the product occurred, while wrinkles occurred on the sides of the product due to uneven thickness. A forming analysis was conducted for the major shapes of the product to investigate the causes of Springback. Distortion deformation due to the bead in the center of the product was confirmed to be a large factor. A Springback reduction method of correcting uneven thickness in the product sides, a Springback reduction method of removing the bead, and a correction method of restriking after the final forming were used in a forming analysis to determine the degree of Springback reduction. For the forming method to correct uneven thickness in the sides, deformation was reduced by 12% in the upper side compared to the existing model, but deformation in the inner side increased by 1%. For the restriking forming method, deformation decreased by 25% in the upper side and 13% in the inner side. For the bead removal method, deformation decreased by 28% in the upper side and 13% in the inner side, the largest Springback correction results. This indicates that the bead has a large affect on Springback.

• 한국기계기술학회지
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• 제13권1호
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• pp.105-112
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• 2011

Increasing needs for light weight and high safety in modern automobiles induced the wide application of high strength steels in automotive body structures- The main difficulty in the forming of sheet metal parts with high strength steel is the large amount of springback including sidewall curl and twist in channel shaped member parts- Among these shape defects, twist occurs frequently and requires numerous reworks on the dies to compensate the shape deviation- But until now, it seems to be no effective method to reduce the twist in the forming processes- In this study, a new forming process to reduce the twist deformation during the forming of automotive structural member was suggested- This method consists of forming and restriking of embosses on the sidewall around the stretch flanging area of the part- and was applied in the forming process design of an automotive front side inner member with high strength steel- To evaluate the effectiveness of the method, springback analysis using $Pamstampa^{tm}$ was done- Through the analysis results, the suggested method was proven to be effective in twist reduction of channel shaped parts with stretch flanging area.

• 한국산학기술학회논문지
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• 제16권6호
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• pp.3667-3671
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• 2015

PCB(Printed circuit board) 장착을 주목적으로 하는 포밍공정에서 주름을 발생시키지 않으면서, 실험을 통하여 재료의 두께 변화를 고찰하였다. 실험결과 제 1공정의 포밍 높이는 제 2공정에서의 재료두께 변화에 크게 영향을 미치는 것으로 나타났으며, 제 1공정에서 다이의 입구 모서리는 제품높이 50%정도의 라운드를 가져야 하며, 포밍의 높이는 원래의 제품보다 재료의 두께만큼 높게 하여야 한다. 또한 제 1공정에서 포밍형상을 구현하면 재료의 두께가 85%로 얇아지고 제 2공정에서 리스트라이킹시 재료의 두께가 80%로 얇아진다. 그러므로 정확한 형상을 구현하기 위해서는 재료가 얇아지는 것을 고려하여 다이는 원제품의 형상을 유지하고 펀치는 원제품의 깊이에 재료 두께의 20%이상 더한 값만큼 길이를 길게 하여야 압축의 효과를 얻을 수 있다.