Abstract
This study presents that finite element (FE) simulations of rotary draw bending are improved by taking into account the stiffnesses of the machine axes. The results show the influence of the axis stiffnesses of the bend die, the wiper die, the pressure die and the mandrel on the formation of wrinkles at the inner tube bend. For this purpose the axis stiffnesses are varied in FE-simulations and wrinkle evaluation factors of the final components are determined and compared. Low axis stiffnesses correspond to large axial displacements when force is applied and cause greater wrinkle formation. In addition, practical tests are carried out on the machine to measure the axis displacements and associated forces. The resulting axis stiffnesses are entered into the FE simulation. The final geometry of the bending component of the FE simulation is compared with the geometry of a component produced in a practical test. The consideration of the axis stiffness in the calculation in contrast to ideally stiff axes provides wrinkle heights that are closer to the wrinkle heights in the practical test. The knowledge gained improves the prediction of the component quality and allows the evaluation of axis displacements measured on bending machines. The overall aim of the project is to react to machine-specific axis stiffnesses in the form of process control.
Highlights
The expansion of drive concepts in the automotive industry is increasingly necessitating smaller batch sizes
In the results described below, the influence of machine axis stiffness on wrinkle formation was investigated
The shifting of machine axes under load has an influence on the formation of wrinkles during rotary draw bending, as the variation of axis stiffnesses in finite element (FE) simulations shows
Summary
The expansion of drive concepts in the automotive industry is increasingly necessitating smaller batch sizes. Due to customer demands for a variety of variants and different vehicle types, product individualization will increase Kuhnhen et al [1]. Individual products require set-up procedures at ever shorter intervals to adjust the forming process Borchmann et al [2]. The set-up processes are made more difficult by the fact that the size progression and influence of variables such as axis displacements, structural inhomogeneities and fluctuations in material properties cannot be predicted Tekkaya et al [3]. In order to investigate the effects of axis displacements on the quality of bending components, FE simulations were carried out in this paper. Results of investigations on the influence of axis displacements on the quality characteristic wrinkle formation according to VDI 3431 [4] are presented
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