Hot drape forming by means of a stiffness controlled vacuum bag

A method of conforming a blank onto forming surface sections of a forming tool by drawing a first vacuum against an elastic forming medium for transmitting forming forces from the elastic forming medium to the blank, the method comprising:

• applying the blank to the forming tool;
• enclosing the blank within the elastic forming medium;
• evacuating the elastic forming medium with the first vacuum for allowing the elastic forming medium to stretch and conform the blank to the forming surface sections;
• removing the formed blank, constituting an article, from the forming tool after completion of the evacuation, wherein the elastic forming medium comprises at least one void, and
• applying a second vacuum to the void to achieve a stiffened section of the elastic forming medium corresponding with the location of the void and corresponding with, when the elastic forming medium after the completion lies against the forming tool having the blank in between, a forming surface section of the forming tool, wherein where the blank requires a forming force being larger than that of surrounding sections of the elastic forming medium.