National University of Science and Technology “MISIS”, Moscow, Russia

N. A. Chichenev, Dr. Eng., Prof., Dept. of Process Equipment Engineering, e-mail: chich38@mail.ru
A. O. Karfidov, Head of the Dept. of Process Equipment Engineering, e-mail: a.korf@mail.ru
M. V. Vasilyev, Senior Lecturer, Dept. of Process Equipment Engineering, e-mail: mv@karfidovlab.com
O. N. Chicheneva, Cand. Eng., Associate Prof., Dept. of Computer-Aided Engineering and Design, e-mail: ch-grafika@mail.ru

In the production of thin-walled metal parts, the sheet stamping process is widely used, which is characterized by ease of implementation, high productivity and low operating costs. The issues of determining the parameters of step-by-step bending, which is widely used in the manufacture of thinwalled body parts and whose advantage in comparison with other bending methods is simplicity of implementation and versatility, as well as the absence of special technological equipment and complex deforming equipment, are considered. Step-by-step bending is a method of forming a large bending radius in a sheet metal part by creating a sequential series of V-shaped bends in close proximity to each other. Based on the analysis of the process of stepwise bending of sheet material, dependences are obtained for the bending angle corresponding to one step and for the absolute deviation of the real (polyhedral) outer profile of sheet material during stepwise bending from the given profile in the form of a circle. For the convenience of practical use, the expression for the profile deviation is presented in dimensionless form. The dependence of the bending angle of the stage on the relative stroke (penetration depth into the matrix) of the punch with free (air) bending is obtained, which is used in the development of technological modes of step bending for the production of a number of thin-walled body parts. Recommendations are given on the choice of the number of steps depending on the requirements of the technical specification for the profile of the bent sheet. As an example, the results of calculating the relative and absolute deviation of the polyhedral profile from the number of steps at a bending angle of 90 ° and a bending radius of 100 mm are given; for some cases, the values of the nearest linear dimensional tolerances according to GOST 25346-2013 are shown.

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