Analysis of Dimensional Accuracy of Precision Forged Axisymmetric Components

Abstract
A theoretical analysis for predicting final forging dimensions for precision forged cylinders at various forging temperatures and loads is presented. This has been derived by studying the effects of various parameters such as forging load, forging temperature, die preheat temperature and spark gap on final forged dimensions. Experimental results compare well with theoretical predictions. It has been found for circular forgings that the finish forged diameter increases with an increase in forging load, but if loading is such that it induces an axial stress greater than twice the flow stress of the workpiece material, the dimension of finished product remains constant. Dimensional variation of forgings due to elastic die deflection decreases when forging temperature increases and at high temperatures is insignificant compared to other factors. For a given die preheat temperature, the higher the forging temperature the greater the increase in forging dimension due to thermal expansion of the die. Thermal shrinkage of the forging is the overwhelming factor influencing forged dimensions at medium and high temperatures. Although friction, work hardening and heat loss were neglected, the close agreement between experimental and theoretical results shows that the theory can be usefully employed in practical situations.

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