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Sustainable and smart shaping process for radial innovation in European metal forming manufacturing

Final Report Summary - SCULPTOR (Sustainable and smart shaping process for radial innovation in European metal forming manufacturing)

As an alternative to conventional stamping and deep drawing processes which are based on big and costly dies and presses, the shaping process proposed in the 'Sustainable and smart shaping process for radial innovation in European metal forming manufacturing' (Sculptor) project was based on the incremental sheet forming technique (ISF), a new, clean and affordable process.

ISF consists of the gradual plastic deformation of a metal sheet by the action of a spherical forming tool whose trajectory is numerically controlled. Thus, complex shapes can be achieved eliminating the dies or using a simple support die. The process can be carried out in either in a standard CNC milling machine or a robot. One of the key advantages of ISF is that initial investment costs are around a 5-10 % of those of conventional stamping process since dies are eliminated or significantly simplified (one support die with simplified geometry and/or made of cheaper materials).

Moreover, ISF is a quite more flexible method since different geometries can be obtained in the same machine just by adapting the CAD programs and optimising the process parameters. In spite of the mentioned advantages, the process has a limited industrial penetration yet because it is not completely flexible (support dies are needed most of the times), not self-controlled (cracks and defects are unpredictable) and not fully optimised (parts lack of geometrical accuracy and uniform thickness). In order to solve those problems, several aspects need further investigation and a deeper knowledge has to be reached.

The Sculptor project targeted to achieve a significant advance in ISF. On the one hand, while conventional ISF usually requires a support die, the project proposed a new ISF concept where the support is replaced by a second forming tool. Thus, the part is formed by the action of two opposite tools. Path of both tools were controlled in terms of position, tilt, speed and force. The new ISF process provides compared to conventional ISF with the capabilities for shaping more complex and larger geometries and decreasing processing times. The control of the two generic forming tools also provides with a higher flexibility since a die with a dedicated geometry will be no more required.

On the other hand, conventional ISF limitations have only been solved for simple geometries through multi-stage strategies where consecutive optimised intermediate surfaces are numerically calculated to get the desired geometry without wrinkles or cracks. In this sense, the Sculptor project researched into more general strategies, developing and optimising computational modelling tools and a specific process methodology.

Major achievements of the project can be summarised as follows:

- Two Sculptor prototypes have been developed and some basic shapes have been produced to test the feasibility of the process.
- Prototypes of two sensory forming tools (thickness and force measuring) as well as a sensory blank holder (force measuring) have been developed and tested. Their potential to monitor ISF processes has been demonstrated.
- A one-step model allows estimating part thickness with accuracy quickly. A full-scale numerical model allows predicting strains for both conventional and Sculptor ISF but computation times are still very high for complex geometries.
- Important contributions to the development of a methodology for ISF have been made in terms of machine parameters, lubricants and forming strategies. These contributions have made possible to fabricate two automotive applications using conventional ISF.

It can be concluded that the Sculptor project has made relevant contributions to the take up of the ISF. New challenges involve now to fabricate parts using ISF in advanced materials, with a high complexity / accuracy for a broad range of industrial sectors as well as the development of ISF capabilities with the robustness and reliability to fulfil industry requirements.

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