Comparison of Offset and Wiping Z-Die Designs for Precision Z-Bent Part Fabrication

Abstract

In recent years, the requirements for high dimensional precision on Z-bent shaped parts have become increasingly stringent. To attain these requirements, the suitable selection of the Z-die bending type has to be considered much more strictly. In this research, two types of Z-bending processes, offset Z-die bending and wiping Z-die bending, were investigated using the finite element method (FEM) to identify the spring-back characteristics and dimensions of Z-bent shaped parts. In the case of offset Z-die bending, the spring-back characteristics on both bend angles were similar. In contrast, in the case of wiping Z-bending, the spring-back characteristics on both bend angles were different. In addition, the dimensions of the Z-bent shaped parts were investigated. It was found, in the case of wiping Z-bending, that web thinning was generated and the outer bend radius was out of tolerance. To validate the FEM simulation results, experiments were carried out. The FEM simulation results showed good agreement with the experimental results in terms of the bend angles and the overall geometry of the Z-bent shaped parts. To achieve precise Z-bent shaped parts, the suitable selection of Z-die bending type in the Z-die bending process is very important.

Wiping Z-bending die design for precise part fabrication

“…Twodimensional, implicit, quasi-static FEM simulations were performed with DEFORM-2D. In accordance with previous studies , (Thipprakmas et al, 2018), (Thipprakmas and Phanitwong, 2012), , the punches, dies, and blank holders were modeled as rigid materials. The workpiece was modeled as an elastoplastic material, and it was meshed by approximately 4,000 rectangular elements.…”

“…Due to excessive deformation of the elements, adaptive remeshing was performed every three steps to prevent calculation divergence. In the present research, aluminum A1100-O (JIS) was used as the workpiece material, and its properties were taken from tensile test data (Thipprakmas and Komolruji, 2016), , (Thipprakmas et al, 2018). The other material properties are given in Table 1, where E, ν and u denote the Young modulus, Poisson's ratio and ultimate tensile stress, respectively.…”

“…The other material properties are given in Table 1, where E, ν and u denote the Young modulus, Poisson's ratio and ultimate tensile stress, respectively. Based on the contact surface model defined by the Coulomb friction law, in accordance with previous research (Ghaei et al, 2015), (Leu, 2017), (Thipprakmas et al, 2018), friction coefficients () of 0.10 were applied. The three investigated bend angles were 90, 120, and 150.…”

“…This has emphasized that the Z-bending process must be improved; hence, many more studies need to be performed to generate new findings and insights. In the past, a few studies have investigated the Z-bending process (Thipprakmas and Komolruji, 2016), , (Thipprakmas et al, 2018). However, the information gained from these studies has not been sufficient to achieve good Z-bending die design and fabricate precise Z-bent parts, especially asymmetrical Z-bent parts.…”

“…This process can make two bends in one stroke, thereby removing the need for a secondary bending operation and decreasing the time and cost of production (Cheok et al, 2002). In previous studies (Thipprakmas and Komolruji, 2016), , (Thipprakmas et al, 2018), the bending mechanism and spring-back characteristics were investigated on asymmetrical Z-bent parts. The effects of the bend radius and bend angle on spring-back characteristics were clearly clarified through stress distribution analyses.…”