ISMR September 2026 | Page 61

Image: Felix Monza.

New enhanced process

“ Cycle times in sheet hydroforming are typically longer than in conventional sheetmetal forming processes, such as deepdrawing. Even when processing continuous strip material from coil stock, production rates of only six to eight strokes per minute are generally achievable. This is primarily because the process steps of‘ opening and closing the press’,‘ building up the clamping force’ and‘ forming’ are performed sequentially,” said Fraunhofer IWU.

However, Fraunhofer IWU has completely redesigned both the process sequence and the tool structure using its passive highpressure sheet metal forming technology, enabling these steps to occur simultaneously. In passive HPSF, the forming pressure is generated directly within the tool through a hydraulic cylinder. As the press closes, the clamping force automatically generates the required fluid pressure. Standard presses can be used, eliminating the need for a separate highpressure water-hydraulic system. Combined with coil-fed production, the technology enables the manufacture of bipolar plates at rates of up to 60 cycles per minute for the first time.

“ At Fraunhofer IWU, passive HPSF is being researched primarily for manufacturing bipolar plates used in fuel cells and electrolyzers. However, the enhanced process could also be applied to the production of smartphone

Gas springs

Forming medium pressure Cylinder

Inlet valve

Combined with coil-fed production, the technology enables the manufacture of bipolar plates at rates of up to 60 cycles per minute for the first time.

housings, either replacing or complementing deep-drawing processes. Cost-effective tooling enables economical series production even for smaller sheet metal components, which are currently produced by stamping,” added the researchers.

Additional benefits of passive HPSF include greater design freedom, improved surface quality – because the sheet is uniformly pressed against the die surface by the fluid – more consistent material thickness distribution, and very short cycle times.

Rendering of lounge furniture as an example application for metal-plastic hybrid components that can be manufactured using the combined hydroforming and flow-pressing process.

Lower die

Moving piston

Forming medium pressure

Pressure relief valve

Hydraulic forming and flow pressing

Another breakthrough by the IWU team is combining hydraulic forming and flow pressing, making it much easier to manufacture hybrid metal-plastic composite components than previously.

Metal-plastic hybrid components are used in a wide range of products. In the automotive industry, for example, structural elements of instrument panels( cross-car beams) and front-end assemblies often contain components with permanently bonded plastic and metal elements. Metal and plastic parts are also frequently joined together in furniture legs and similar products.

Today, manufacturing these hybrid components often relies on a combination of hydroforming and injection moulding. However, integrating these technologies requires combining two fundamentally different processes – each with demanding requirements as to equipment, process control and expertise – within a single production system. The result is substantial capital investment in both machinery and tooling, often placing such solutions beyond the reach of small and medium-sized enterprises( SMEs).

To address this challenge, Fraunhofer IWU with Chemnitz University of Technology, injection-moulding specialist Schicktanz GmbH, lightweight hydroforming press manufacturer IWC Engineering and industrial designer, Felix Monza, have developed a new process combination consisting of tube hydroforming and simultaneous flow pressing of plastic components.

“ The key difference from the established combination of internal high-pressure forming( IHF) and plastic injection moulding is that the plastic component is introduced into the tool as a pre-manufactured extruded or

ISMR September 2026 | ismr. net | 61