Determination of preform shape to improve dimensional accuracy of the forged crown gear form in a closed-die forging process

Among the many factors that affect the dimensional accuracy of the closed-die forging of a crown gear form, an important factor is well designed shape of the initial billet or preform, as this can markedly improve the dimensional accuracy of the forged product. The paper presents kinematically admissible velocity fields for closed-die forging of the crown gear form which take into account the profiled teeth chosen kinematically by approximating these as trapezoidal teeth and then simulates using the velocity fields to obtain upper bound to the load and the deformed configurations of the various shaped solid billets or preforms. Based on these simulations, the experimental investigations were carried out to obtain a forged crown gear form with the good quality, using two types of model materials, lead and plasticine. The preform shape which improved the dimensional accuracy of the forged crown gear form is presented and the results commented upon.