Development of an innovative hydraulic press for incremental forming: machine and process evaluation using a hybrid two-step process

• A newly developed machine concept for SPIF based on a hydraulic press. • Higher force values in vertical direction compared to conventional SPIF machines. • Advancement of ISF into the area of difficult-to-form materials • Integration of real-time monitoring and control for improved forming accuracy. • Sheet thinning minimisation by executing bulging before SPIF. Developing individual/personalised products requires flexible forming processes, which are limited by insufficient sheet thickness distribution and inadequate mechanical properties of the formed material. One group of forming processes with greater flexibility are incremental sheet metal forming (ISF) processes, the simplest representative of which is single-point incremental forming (SPIF). In order to improve the sheet thickness distribution, a pre-bulging process with subsequent SPIF is carried out in this study. Experimental results show that the integration of a pre-bulging step in a hybrid forming process leads to a more uniform final sheet thickness and reduces tip thinning compared to SPIF. This study focuses on the development of a hybrid machine based on a servo-hydraulic press to achieve sufficient forming accuracy with SPIF on difficult-to-form materials. SPIF is performed by increasing the flexibility of the hydraulic machine through the use of ball runner blocks mounted on the press bed, which allow movements in the horizontal plane. The developed hydraulic forming setup enables a significantly higher vertical force capacity, extending the application of SPIF to high-strength materials such as DP590 steel. This approach demonstrates a novel, scalable path for SPIF for industrially relevant materials and overcomes significant limitations of conventional CNC-based SPIF systems.