Residual Stresses in Robot-Assisted Drag Finishing of Metal Additive Manufactured Components

Metal Additive Manufacturing (AM), a great option in the aerospace industry for having design flexibility, due to its inherent process characteristics, needs surface post-processing to achieve desired surface integrity. Although drag finishing using abrasive media yields satisfactory surface finishing, its main disadvantages are the processing time and the modification of the geometry of the workpiece due to the uncontrolled material removal.

A robot-assisted drag finishing process is developed to overcome these limitations. The system integrates a 6-axis robotic arm that precisely manipulates the workpiece within the abrasive media in a centrifugal disk finisher, to minimize processing time and improve surface integrity, including the residual stresses.

In this work, the surface and subsurface residual stress was measured by X-ray diffraction using the cos α method after polishing with varying process parameters (part orientation, media shape, media size, and media velocity) to understand their effects on the residual stresses in finishing AISI 316L stainless stress. Experimental tests were performed through the Plackett-Burman screening Design of Experiments method. A numerical modeling of the process was also developed to understand effects of the process parameters on residual stresses. This work permitted the determination the significant machining parameters that induce compressive residual stresses in the surface and subsurface of metal AM components.

Keywords: Additive Manufacturing, Drag Finishing, Residual Stresses.