the formation of a bellows made up of a stack of a predetermined number of ring - convolutions and having an intermediate plate supported within said stack is achieved by supplying several thin metal rings , each having inner and outer edges . a pair of these metal rings are positioned in contiguous relationship and their adjacent inside edges are welded together to form a ring - convolution . this process is repeated until a sufficient number of ring - convolutions are made to eventually make the desired bellows . before these separate ring - convolutions are fused to each other , an intermediate plate and a support ring are made . the intermediate plate is a disc of metal that is sized smaller than the inside diameter of the rings and is secured to the support ring . the support ring is then positioned between two formed ring - convolutions in contiguous relationship and the three abutting outside edges are welded to each other to form a support plate convolution . the already made ring - convolutions and the support plate convolution are then stacked in the desired order and in contiguous relationship . all not - yet welded adjacent outside edges of said ring - convolutions and said support plate convolution are then welded to form the bellows . a bottom plate is formed and welded to the outside edge of the bottommost ring - convolution and a top ring is finally welded to the uppermost convolution to complete the bellows . the top ring is meant to be welded to a base plate of an infusion pump .