## 4 PBF-LB/M Process
### Process Optimization
#### 4.2.3 Process Monitoring and Quality Control to Improve Component Life Service  
In PBF-LB/M, the effective integration of process monitoring and quality control is pivotal for optimizing component longevity and advancing sustainability. Continuous monitoring of process parameters enables real-time detection of deviations that could result in defects like porosity or incomplete fusion. By employing rigorous quality control measures informed by this monitoring data, only components that adhere to stringent quality standards are produced, thereby reducing the risk of premature failure and extending service life. Additionally, minimizing defects and rework enhances component reliability and decreases material waste and energy consumption, thus contributing significantly to the sustainability of the PBF-LB/M process. As mentioned in the previous section, enhancing the BR involves increasing the laser movement speed, which reduces energy density. Consequently, this raises the likelihood of producing parts with specific porosity defects, such as a lack of fusion [163]. Therefore, it is essential to ensure that higher productivity does not compromise the quality of the parts. These defects can reduce the lifespan of the parts, potentially leading to premature failure and disrupting the sustainability chain. PBF-LB/M, like all conventional manufacturing methods, requires robust quality assurance procedures and advanced tools to effectively manage and certify the quality of fabricated components. In PBF-LB/M, the reliability and longevity of produced components are significantly influenced by factors such as defects, residual stresses, and microstructural inconsistencies [164]. Specifically, the PBF-LB/M process involves complex interactions between laser, powder, and substrate, and even minor deviations can lead to defects such as porosity, warping, or structural weaknesses [165]. Aluminum alloys processed by PBF-LB/M are characterized by a limited absorption of laser energy to the wavelength of YAG Laser, leading to inconsistent melting and promoting the formation of oxides, which can cause porosity and affect the mechanical properties of the final part [166]. Additionally, the rapid cooling rates associated with PBF-LB/M can induce significant residual stresses, resulting in distortion and cracking [167]. Effective monitoring and quality control are, therefore, imperative to address these challenges and enhance the service life and structural integrity of Al PBFed components. Both in situ (or in-line) monitoring techniques, which provide real-time data on process characteristics, and ex-line monitoring techniques, such as post-build inspection and analysis, play crucial roles in ensuring the quality and durability of these components. In situ monitoring provides continuous oversight of process parameters and material behavior, enabling early detection of issues and facilitating immediate corrective actions. This real-time feedback loop is crucial for maintaining the desired quality and performance of the final parts. These techniques facilitate increased process efficiency by optimizing operational parameters such as laser power and scan speed using live data, thereby minimizing material waste and reducing production times. In addition, in situ monitoring reduces the necessity for extensive post-build inspections and rework by addressing potential issues during the build process. Moreover, it supports improved predictive maintenance by providing critical data on equipment wear and performance, which enhances equipment reliability and decreases downtime [164].