Abrasive flow machining of asymmetric spur gear forging die

Abrasive Flow Machining (AFM) is a relatively novel and non-usual surface finishing process that is performed by the movement of abrasive media through the surface. Conventional surface finishing operations are limited to regular geometries as circular, rectangular or flat shapes. With the help of the flowability of media, AFM is not limited by simple geometries especially for internal shapes like forging and extrusion dies. In this study, AFM was carried out for finishing the asymmetric spur gear precision forging die. A mathematical model was derived to obtain material removal with respect to the number of AFM cycles. CFD analysis has been used to predict the flow characteristics of the flowing media and the stresses exerted on the die surface. The material removal depth (i.e. dimensional change) along the gear tooth profile was investigated by using two AFM models; circular- and gear-shaped mandrel models. The white layer formed after the WEDM process was successfully removed by AFM. The resulting surface roughness values are in between polishing and super-finishing ranges. The experimental results are in agreement with the presented mathematical model. The mathematical model is suitable for both circular- and gear-shaped mandrel models. Although circular-shaped mandrel is simple and economical, the use of gear-shaped mandrel results in a more uniform surface finish and a higher amount of material removal. Due to the amount of material removal depth is non-uniform through the tooth profile, some amount of machining allowance must be considered during tool path generation for WEDM cutting.