## 5 Post-Processing
### Strategies to Reduce Surface Post-Processing Operations  
Managing surface roughness during manufacturing is essential for producing ready-to-use components, minimizing the need for extensive post-processing. When compared to subtractive manufacturing, the limited surface finish and dimensional accuracy of PBFed aluminum components restrict their broader adoption. For this reason, optimizing PBF-LB/M process parameters is crucial for enhancing surface quality, which directly affects the mechanical performance and dimensional accuracy of 3D-printed parts [195]. By fine-tuning the PBF-LB/M parameters, smoother surfaces can be achieved, significantly reducing the reliance on post-processing methods like machining or polishing [196]. This approach not only boosts production efficiency but also promotes sustainability by conserving energy, minimizing material waste, and lowering the overall carbon footprint. Surface roughness refers to the micro-scale irregularities on a material surface and is a critical factor for the mechanical properties, especially for dynamic ones such as fatigue strength [197; 198]. The literature has amply demonstrated that surface roughness is pre  
Figure 12: Comparison of energy efficiency and property enhancement across various heat treatment methods for PBFed aluminum alloys. dominantly influenced by three key factors: irregular solidification of the melt pool driven by process dynamics, the adhesion of powder particles to the surface, and the staircase effect [199; 200; 201]. There are various methods for characterizing and quantifying surface roughness, with the most widely used relying on mathematical parameters that describe the surface profile. Roughness values can be calculated either along a single profile (line) or across an entire surface (area). These parameters are generally classified into three categories based on their function: amplitude parameters, spacing parameters, and hybrid parameters. The most used surface roughness parameter for PBF-LB/M components is Ra, also referred to as the arithmetic average height or center line average. Ra is widely accepted in general quality control, representing the average absolute deviation of surface irregularities from the mean line over a defined sampling length [201]. Attaining the desired surface quality and dimensional precision necessitates the careful selection of appropriate PBF-LB/M parameter combinations. [PERSON] et al. demonstrated that the variation in surface quality of 7075 alloy samples is significantly influenced by both laser power and volume energy density [202]. In particular, they observed that by keeping constant the scan speed, surface roughness consistently decreased with increasing laser power. A parabolic trend was instead seen by correlating surface roughness with Volumetric Energy Density (VED), a crucial parameter that combines several process parameters (laser power, scanning speed, hatch spacing, and layer thickness) to provide an integrated measure of energy applied per unit volume of the powder bed. The roughest surface was observed at a low energy density of VED = 43 J/mm\({}^{3}\), while a smooth, dense surface was obtained at VED = 313 J/mm\({}^{3}\), and a relatively rough surface at a high energy density of VED = 1565 J/mm\({}^{3}\). The same trend was noticed by [PERSON] et al. [203] on AlSi10 Mg parts. They investigated the correlation between VED and surface roughness, paying attention to the effects on the five faces of the PBFed cubes. Their study demonstrated that as energy density increased, the roughness of the five faces initially decreased before rising again, whereas the roughness of the top surface exhibited a slight increase. The most favorable surface quality was achieved at energy densities of 175 and 200 J/mm\({}^{3}\). In another study on the surface roughness of PBFed AlSi/Mg, the findings showed that laser power and scan speed significantly impacted surface roughness [204]. Another parameter that influences surface roughness is the use of contour scans.