A Study on the Nose Radius Influence in Press Brake Bending Operations by Finite Element Analysis

Abstract

The sheet metal bending is one of the metal forming processes with the simplest geometric interpretation and usually a 2D analysis is considered. The bend over a sheet metal blank consists of a V shape forming by using a punch, with a certain nose radius, forcing the plate against an open die, with a V section. The forming result is a part with an angle obtained between the V legs, flanges, which is known as bending angle. The operation to get the required V angle is called air bending, or free bending. The most common used machines for this forming process are press brakes, special long presses, where the tools, punch and die, are attached to. With the spread use of CNC machines, and their computer control capabilities, most of them using graphical user interface (GUI), became important to get the required shape at first trial. Beyond the required bending angle obtained with just one hit, it is also important to position the gauge system in order to get the successive flange lengths to complete the programmed shape. The main variables controlled by the CNC are the punch penetration inside the die and the position of the back gauge, which is determined by the bend allowance. However this penetration is not the only responsible for the resulting bending angle and the gauging position is not the only responsible for the flange length. Additionally, the radius inside the V shape edge, known as bending radius, influences the geometry and correspondingly the bend allowance. Some authors believe that the punch nose radius has direct influence, both in the bending angle and bend allowance. In this paper, results are presented describing the use of finite element analysis as an aid in the prediction of the inside bending radius, that influences both punch penetration for the final bending angle and the bend allowance for the final flange length. From the air bending analysis, a natural inside bending radius is presented as an important variable in these kind of processes, as well as its minor dependence on the punch nose radius.

Forming and springback prediction in press brake air bending combining finite element analysis and neural networks

“…The inside bending radius ( r i ) incorporated in equation (1) can be determined from the die opening, according to the industry practice used expression (equation (2)) 2…”

“…Among the most common sheet forming techniques, the press bending operations can probably be considered its most fundamental variant. 1,2 However, different forming methods can be used to bend a sheet, like air bending, coining, bottoming and others. Offering the highest flexibility, by making it possible to obtain different bending angles using the same set of tools, air bending is often the preferable method.…”

Application of Machine Learning to Bending Processes and Material Identification

“…Among different forming techniques, sheet bending and stamping can be considered the most important variants in forming industry. These techniques have been continuously improved in recent decades to meet the growing need for lightweight metallic components in the automotive sector in order to address environmental concerns about energy efficiency and emissions [1,2]. To bend a sheet metal material, different methods can be used such as air bending, coining, and bottom bending.…”