U.P. Singh

A process model for air bending

A so called `three-section? model for air bending is presented. It is assumed that a state of plane strain exists and that Bernoullis law is valid. The material behaviour is described with Swifts equation, and the change of Youngs modulus under deformation is addressed. As compared with other models, the model described in the paper is capable of generating information such as required punch displacement and the unfolded blank size, very accurately. With in-process measurement of the spring-back angle, the punch displacement can be calculated even more accurately.

Finite element simulation of the punching/blanking process using in-process characterisation of mild steel

Abstract Punching/blanking is among the oldest and most frequently used sheet metal forming processes. In spite of this, the definition of process parameters as a function of key characteristics of the process and blank material properties is in practise usually still done in an empirical manner. This paper reports an investigation into the behaviour of the blank material during the process through finite element simulations, analytical modelling and experimental work. The objective is to contribute towards the development of a system for the on-line characterisation of the blank material properties during the punching/blanking process. The finite element method was applied through the use of ABAQUS code.

Design study of the geometry of a punching/blanking tool

The cost of tooling in sheet metal industries contributes a considerable part to the overall cost of manufacturing a component. It is therefore imperative to keep down this cost by ensuring that the tool works for a long period in production without interruption. One way of achieving this objective is to reduce the stress on the tool during punching/blanking. This paper deals with the study of this problem by using the finite-element technique. 3-D finite-element models of various type of punching/blanking tools have been developed, these models enabling the analysis of the effects of variations in tool geometry on the punching/blanking force and on the deformation of the punch, a parameter highly relevant to the assessment of tool performance in terms of the accuracy of the manufactured components. The model caters also for variation in the characteristics of the tool material, in the sense that a highly wear-resistant tool is normally composed of carbide tips around its cutting profile. Computed results by FE models are checked against design standards by American Society of Manufacturing Engineers (SME). Some suggestions are offered as to how the efficiency of a punching/blanking tool can be improved.

Numerical simulation of the influence of air bending tool geometry on product quality

Abstract The quality of a bend is determined by the accuracy and consistency of the angle along the length of the part. This accuracy is directly related to the penetration of the tool in the die. Small variations in tool penetration can cause relatively large changes in bend angle. Such variations are caused by changes in the repeatability of the tool stopping point, by deflections of the press brake beams and by distortions of the tooling. Earlier studies [Int. J. Mech. Sci. 22 (1980) 583; J. Mater. Process. Technol. 35 (1992) 129; Precision bending of sheet metal, Master’s Thesis, University of Twente, 1992; A finite element simulation of free bending, in: Proceedings of the Second International Sheet Metal Conference, SheMet’94, University of Ulster, 1994, pp. 201–211] on finite element modelling of the air bending process assume that the tooling is perfectly rigid. The present 3D finite element model of press brake air bending tools allows calculation of elastic distortions in typical tools and relates the distortion to the accuracy of the formed part. The finite element model has been validated by experiments conducted on a commercial press brake. Some suggestions are made for improvements to the direct and cross stiffness of the tools which should lead to improved alignment of the tool and die and, in turn, to improved product accuracy.

A new analytical model for pressbrake forming using in-process identification of material characteristics

Abstract The paper describes the development of an analytical model of the air bending process based on in-process identification of aerospace material characteristics during pressbrake forming. The parabolic-straight theory is employed in the development of the analytical model using in-process material characteristics. The validity of the model is checked against both the FEM (ABAQUS) results and experimental results.

Computer Aided Design Study of a Die-Set for Punching/Blanking

Die-set for multi-purpose operations such as bending, trimming and punching, are usually complex in design and expensive. Past work on die design indicates that the misalignment of a die and punch caused by the deformation of the die-set directly influences the life of the die and punch. Consequently anything which enables accurate prediction of the magnitude of relative displacements of the die and punch can be of a great help to press-tool designers.