With Hydroforming to a Better Product The Technology for Optimum Performance


In detail: What is hydroforming?

As a pioneer in hydroforming, we deliberately rely on the process for which we are known worldwide as experts for the production of bipolar plates. The advantages of hydroforming are obvious:

Hydroforming – or external high-pressure forming – is an active media forming process. A metal foil is inserted into a tool gravure and expanded into the forming tool with very high pressure by means of a water-oil-emulsion (see sketch).

Thanks to the even pressure distribution over the entire foil surface, an homogeneous material thickness distribution is achieved, and abrupt stress transitions are avoided. This allows forming even the smallest radii. The material spring back remains low.

Explanation of the hydroforming process by means of a sketch

The advantages of hydroforming

With so-called external high-pressure forming, extremely filigree structures can be realized in series using extremely thin materials from 50 μm. In contrast to mechanical forming, which at first glance may seem more cost-effective, especially for series production, hydroforming offers numerous advantages that pay off in the long term.

Since bipolar plate production is all about repeatable precision, attention to detail and high value, we believe that hydroforming is the optimal process – and one of the quality features that makes Graebener® Bipolar Plate Technologies your sustainable competitive edge.

Properties of a Graebener® hydroforming plate and a mechanically produced plate

Criteria Graebener® hydroforming plate Mechanically produced plate
Repeat accuracy in the process Very high


Elasticity after forming Highly elastic through gentle forming with integrated cooling Significantly reduced through strain hardening
Wall thickness variation Very homogeneous over the entire duct cross- section Heterogeneous (constrictions)
Suitability for pre-coated materials Ideal: no friction on the water side Only limited use due to friction in the tool
Contact areas Almost ideal shaping of the flat contact surfaces Good shaping
Use of different material thicknesses in one tool Flexible: different material thicknesses can be used per tool Not possible
Adaptation of the manufacturing parameters in the forming process


Not possible
Tool costs Low: less wear and fewer tools High
Number of tool stages One Several (multi-stage forming tool)


Exemplary Graebener® hydroforming plates

microsection of a hydroformed precoated plate

Foil thickness: 100 μm, Material: Alleima Sanergy® LT (316L)

microsection of a hydroformed plate

Foil thickness: 50 μm, Material: 304L


Foil thickness: 100 μm, Material: Titanium Grade 1

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From the well thought-out bipolar plate to the precisely fitting solution

Phone: +49 2737 989-0

Fax: +49 2737 989-110