PURPOSE: To restrain chamber and stress by forming rolls, to eliminate a stress relief stage, to miniaturize an equipment and to simplify a manufacturing stage by changing a projection-forming direction with forming rolls.
CONSTITUTION: At a 1st stage A, a trimming bead, a partitioning bead and plural beads are formed by forming rolls 21 and at a 2nd stage B projection 23 projecting in the direction opposite to many projections 18 given by the 1st stage A are provided and at the same time the stress of a stock worked in the 1st stage A is relieved and forming is performed to determine the height. Therefore, a plate 101 receives a force bending backward to the direction opposite to the 1st stage A and on the flat part of the plate 101, the projections 18 projecting to one direction as conventional one and the projections 23 projecting to the opposite direction are formed so that the top part of the projections 18 and the top part of the projections 18 do not put one upon another. At a 3rd stage C, the front and rear parts are cut so that the length between them corresponds to an element for a heat exchanger. At the 4th stage D, the front and rear parts are bent in the same direction to obtain an element F as a flange.
YAMAMOTO AKIRA