Effect of Process Parameters on Surface Roughness in Hammer Peening and Deep Rolling

The challenges in die and mold making industry to increase productivity and reduce costs can be addressed by expanding the automation in the process chain. Conventionally the final surface quality is produced by manual polishing operations. This expensive time-consuming production step can be reduced significantly by using machine hammer peening (MHP) and deep rolling (DR). For both processes the emphasis of each process parameter on the resulting surface topographyis largely unknown. This gap of knowledge about significant and non-significant parameters needs to be closed in order to allow a fast process optimization and more economic use of both methods. Therefore this study focuses on figuring out the statistically secured effect of each process parameter on the attainable surface smoothing on cast iron and tool steel. Based on a fractional factorial test design the results of an experimental parameter study are presented and significant parameters are identified. Using a high-speed camera, it may also be proved why an inclination angle between the hammering direction and surface normal is advantageous with regard to the resulting surface quality. Finally, the results are discussed and advices for an industrial use of MHP and DR are given.