FIELD: metal pressure forming. SUBSTANCE: method comprises steps of placing a sheet blank between a deformable punch and a deformable die, the punch has a convex deformable base; clamping the blank in its central part, arranging a mean fibre of the central part in a concrete position relative to a neutral fibre of the punch, of the blank and of the die; then forming a central portion of the blank into a cavity of the die in such a way, that the deformable base of the punch, had been flattened at a clamping stage, restores its initial convex shape; folding a peripheral portion of the blank with the aid of a deformable ring of an elastic non-compressible material and smoothly forcing it to lateral walls of the punch up to formation of a folded edge: making a predetermined number of ribs for compensating length change of that edge, the ribs having desirable shape and dimensions and they are arranged by a predetermined fashion. The apparatus for performing the method includes the punch in the form of the deformable convex base, a rigid container in the form of parallelepiped with a bed and with a cushion of the elastic material. Means for folding the peripheral portion of the blank along lateral walls of the punch include an additional forming member for acting upon an end of the peripheral portion of the blank and the deformable ring of elastic material. All elastic members of the apparatus may be made of the same or different materials, including composite materials, having different rigidity values. The base of the punch and the part of the die, turned to it, may have lens-like shape. The additional forming member has two rectangular frames, between which the deformable ring is arranged. The container of the punch has relief on its lateral surface. EFFECT: enhanced efficiency. 16 cl, 8 dwg
