Effect of Ball Burnishing and Laser Polishing on the Surface Characteristics of Deposited Layers in Hybrid Additive Laminated Tooling

Manufacturing of deep drawing dies is resource-intensive. Recent innovations in hybrid additive laminated tooling seek to reduce these costs and enhance die strength and surface finish by combining sheet lamination with direct energy deposition processes. This study compares the effects of laser polishing and ball burnishing on the surface roughness and hardness of curved surfaces made from 316L-Si stainless steel and Ferro55 tool steel, both used in hybrid additive laminated tooling. The laser polishing process was tested with varying parameters, including laser power (400–1000 W) and feed rates (400–1000 mm/min), defining energy per unit length (λ) as the ratio of laser power to feed speed. Significant improvements in surface roughness were noted, with reductions of up to 80% for Ferro55 at λ = 120 J/mm, and an optimal λ of 85 J/mm for 316L-Si. Using a smaller laser spot diameter (1.6 mm) and reduced hatching distances (0.2–1 mm) enhanced surface roughness and hardness, achieving a maximum hardness increase of 15% for Ferro55 and 10% for 316L-Si. Larger spot sizes (3 mm) and greater hatching distances diminished effectiveness, leading to softer surfaces due to lower energy densities and cooling rates. Ball burnishing was also evaluated with hatching distances of 0.2 to 6 mm, achieving up to 78% improvement in surface roughness for 316L-Si at 0.2 mm. Overall, results indicate that smaller hatching distances benefit both processes, with laser polishing excelling in surface roughness and hardness enhancement. At the same time, ball burnishing provides a viable surface finish under optimal conditions.