Geometric deviations in forging and cooling operations due to process uncertainties

During hot forging, the billet is heated to an elevated temperature, forged to the required shape and cooled to room temperature. Most of the hot forged parts produced, meet the specified geometric tolerances, but some do not. Some of the defective parts can be rectified by machining, others are rejected. Restoring a hot forged part demands extra production cost. Defective parts can be attributed to process variations or uncertainties that occur during production. Such manufacturing anomalies in the metal forming industry can induce heavy losses (e.g. premature failure of equipment, under-fill, folds in part and double hit) during mass production. The objectives of this research are, determining the uncertainties that cause defective parts during hot forging and illustrate a method to determine parameters that control the trade-off between rejected parts and rectifiable parts. This information will aid in reducing production costs of the forgings. The uncertainties are demonstrated in this research by simulations of the forging and cooling processes. Since, uncertainties in the field of metal forming have never been considered in the design process, quantifying the effects of the process uncertainties would be the first step towards reducing geometric variation and related production costs. Also, incorporating the process uncertainties into the forging and cooling process design leads to better quality parts.