Method for producing a camshaft for an internal-combustion engine

A method for producing a camshaft for an internal-combustion engine, the method comprising:

• forming a metal tubular element comprising contiguous portions of different thicknesses, the tubular element having cam locating portions and non-cam locating portions, the cam locating portions having larger thicknesses than the non-cam locating portions;
• receiving the tubular element in a main cylindrical cavity of a die;
• said main cylindrical cavity comprising a plurality of cam forming cavities comprising widened portions set axially apart from one another by a plurality of non-cam forming areas, for forming the cams of a camshaft, the non-cam forming areas having interior surfaces for contacting the tubular element with smaller diameters than interior surfaces of the cam forming cavities;
• aligning a first portion of the cam locating portions with a first widened portion of the widened portions, aligning a second portion of cam locating portions with a second widened portion of the widened portions, aligning a third portion of the cam locating portions with a third widened portion of the widened portions;
• wherein each of said widened portions of the main cavity of the die has axially opposite ends having a diameter that varies progressively between a minimum value and a maximum value so that the cams of the camshaft are obtained with a corresponding shape, such that opposite ends of the cams have a diameter that tapers from a minimum value to a maximum value;
• introducing a high-pressure fluid in an interior cavity of said metal tubular element to expand said metal tubular element into a first cavity of said die and a second cavity of said die such that an outside surface of the tubular element contacts an inside surface of the die to form a first cam and a second cam, said first cavity comprising a first cavity of said plurality of cam forming cavities and said second cavity comprising a second cavity of said plurality of cam forming cavities, the first cam having a first cam shape corresponding to said first cavity and the second cam having a second cam shape corresponding to said second cavity;
• the first cam and the second cam comprising cams of a plurality of cams of the camshaft, the camshaft formed in a single piece;
• wherein the high-pressure fluid comprises a gas at a pressure of between 400 and 800 bar and at a temperature of between 850° C. and 950° C.;
• and
• wherein for the forming operation using high-pressure fluid a composite die is used, with radially mobile parts in positions corresponding to the portions of the tubular element that are to form the cams.