Forming of light-weight gear wheel by plate forging

A forging process is proposed to form light-weight gear wheels for the valve timing system of engine. The cross-sectional shape of the gear has a hollow space at the back of each tooth to reduce the weight by maintaining the rigidity. First, a cup shaped pre-form with a boss is made by upsetting, deep drawing and burring. Then the gear teeth are formed on the side wall by extrusion with a small reduction in area and subsequent axial compression. It is shown by experiment that the proposed process can produce satisfactory products.