Rubber pad forming (RPF) is a novel method for sheet metal forming that has been increasingly used for: automotive, energy, electronic and aeronautic applications [1]. Compared with the conventional forming processes, this method only requires one rigid die, according to the shape of the part, and the other tool is replaced by a rubber pad [1]. This method can greatly improve the formability of the blank because the contact surface between the rigid die and the rubber pad is flexible. By this way the rubber pad forming enables the production of sheet metal parts with complex contours and bends. Furthermore, the rubber pad forming process is characterized by a low cost of the die because only one rigid die is required [2]. The conventional way to develop rubber pad forming processes of metallic components requires a burdensome trial-and-error process for setting-up the technology, whose success chiefly depends on operator’s skill and experience [4][5]. In the aeronautical field, where the parts are produced in small series, a too lengthy and costly development phase cannot be accepted. Moreover, the small number of components does not justify large investments in tooling. For these reasons, it is necessary that, during the conceptual design, possible technological troubles are preliminarily faced by means of numerical simulation [4],[6]. In this study, the rubber forming process of an aluminum alloy aeronautic component has been explored with numerical simulations and the significant parameters associated with this process have been investigated. Several effects, depending on: stamping strategy, component geometry and rubber pad characterization have been taken into account. The process analysis has been carried out thanks to an extensive use of a commercially finite element (FE) package useful for an appropriate set-up of the process model [7],[8]. These investigations have shown the effectiveness of simulations in process design and highlighted the critical parameters which require necessary adjustments before physical tests.

In order to value the process of variables influence in sheet metal hydroforming, a special hydroforming cell has been developed. Generally, sheet hydroforming is obtained using appropriate press tooling. This option requires large investments completely dedicated to this technology of production. As an alternative, conventional hydraulic presses can be used for sheet hydroforming in combination with special hydraulic tooling named “hydroforming cells”. A special “hydroforming cell” concept has been developed to perform experimental analysis for different shapes using the same tooling set up. CAE tools had a strategic role just to develop the best layout and to find the optimum solutions for the process variables. FEA has been used to define the distribution of the blank holder variable forces: a solution which implies the use of twelve independent actuators have been implemented. The position and the load path of each one of them has been chosen for each formed shape, in accordance with the FEA results. Customized actuators have been used to solve interferences between mechanical parts of the hydroforming cell. For this specific aspects the virtual 3D design was necessary for the appropriate decisions. The developed process system is very effective so that is possible to set up experimental campaigns for sheet hydroformed components.

In order to perform a successful sheet metal forming operation and to avoid shape deviations and tearing and wrinkling defects, process and material variables, such as tools geometry, blankholder force, friction, blank shape, sheet thickness and material properties, should be optimized. One of the main parameters which must be defined at the beginning of any sheet metal forming process design is the initial blank shape and its main dimensions [1]. In this paper, the authors' attention is focused on a non-conventional sheet HDD process for which optimal blank shape and dimensions are not fully explored yet [2]. It will be demonstrated that, when the traditional One Step finite element method calculation, realised through the implicit code, is applied to HDD, the process shows various limits. In fact, while the One Step analysis is able to predict the optimal initial blank for the traditional Deep Drawing (DD) process, the same blank could not be the optimal one in a HDD process. The goal of this paper is to develop a methodology by which, with the aid of optimization algorithms, it will be possible for the user to define the best shape and dimensions for the initial blank in HDD processes, even when starting from the blank obtained by a One Step analysis.

Sheet hydroforming has gained increasing interest in the automotive and aerospace industries because of its many advantages such as higher forming potentiality, good quality of the formed parts which may have complex geometry. The main advantage is that the uniform pressure can be transferred to any part of the formed blank at the same time [1]. In this paper, a “shape factors” set has been defined with the proper goal to understand if it can be used to help engineers to define “process rules” for the studied non conventional technology [2]. A specific prediction model, obtained thanks to a numerical factorial fractional plane, has been used in order to preview the process responses vs each defined shape factor. These shape factors have been used to track the process performances through their variation thanks to the usage of the numerical simulation that has been validated with an appropriate experimental campaign executed thanks to the usage of a specific equipment properly designed.

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