Device and method for expansion forming

A method for expansion forming of an article, comprising the steps of:

• arranging a blank having an inner hollow space in the cavity of an expansion forming tool;
• pressurizing a pressure medium in the hollow space of the blank in such manner that the blank is forced against the wall of the cavity, the blank being thus expanded into an article shaped according to the shape of the cavity;
• exerting pressure on a first outer face of the expansion forming tool and equalizing, during the expansion forming, pressure differences between different portions of said first outer face;
• and
• exerting pressure on a second outer face of the expansion forming tool and equalizing, during the expansion forming, pressure differences between different portions of said second outer face, the first and the second outer face being located opposite one another and oriented away from one another.

A device for expansion forming of an article, preferably used in conjunction with a press, comprising:

• an expansion forming tool, which comprises at least one cavity adapted to receive a blank having an inner hollow space;
• at least one pressure intensifier, which is adapted to pressurize a pressure medium in the hollow space of the blank in such manner that the blank is forced against the wall of the forming space, the blank being thus expanded into an article shaped according to the shape of the cavity;
• and
• a pressure transmitter, which is applicable to an outer face of the tool for exerting pressure thereon and which is adapted to equalize, during the expansion forming, pressure differences between different portions of said outer face, the pressure transmitter comprising a flexible plate, which plate is provided with a seal along its circumference and defines a pressure cell adapted to be filled with a liquid, the inner forming forces in the tool being intended to be compensated for by a liquid pressure from the pressure cell, which is transmitted through the flexible plate.