## 4 PBF-LB/M Process
### Process Optimization
#### 4.2.2 Strategies to Improve Productivity  
One of the main challenges in AM technologies is their relatively low build rate, which makes the production rate unsuitable for efficient mass production compared to traditional manufacturing methods. For instance, while PBF-LB/M systems deposit material at rates of only hundreds of grams per hour, other methods achieve deposition rates measured in kilograms per hour, and processes like forming, stamping, and casting reach rates of hundreds of kilograms per hour [147]. To enable widespread industrial adoption, PBF-LB/M must develop a scalable architecture that significantly increases deposition rates by several orders of magnitude while still preserving the geometric flexibility inherent in AM [148]. In the PBF-LB/M process, sustainability and productivity are closely interconnected. As a result, understanding the factors that influence component production time is crucial for identifying solutions that improve both the industrial scalability of PBF-LB/M and its environmental impact. Recently, [PERSON] et al. summarised the complexities of the PBF-LB/M process, highlighting the various factors affecting production time in the Ishikawa diagram shown in Figure 9 [149]. Methods for enhancing productivity in the PBF-LB/M process can be grouped into several areas, including adjusting process parameters, utilizing advanced equipment (such as multiple laser systems or polar coordinate setups), and adopting hybrid production systems. Figure 9: Ishikawa diagram illustrating the factors that impact production time in the PBF-LB/M process [149]. One of the most widespread approaches to speed up PBF-LB/M productivity is by selecting optimal combinations of process parameters to maximize the build rate. [PERSON] et al. [150] defined the Build Rate as Equation (2):  
\[BR\left(\mathrm{cm^{3}/h}\right)=hd\times l\times\
u \tag{2}\]  
where \(\
u\) is the laser speed, \(hd\) is the hatch distance, and \(l\) is the layer thickness. Based on this equation, it is clear that increasing the scan speed, hatch distance, and layer thickness can significantly enhance both the productivity and sustainability of the PBF-LB/M process. However, increased \(\
u\), \(hd\), and \(l\) also result in reduced energy density, which can lead to lower-density products, with the occurrence of a lack of fusion porosities. To avoid the presence of defects that could have a detrimental effect on mechanical properties, it is, therefore, essential to balance productivity with part quality [151; 152]. [PERSON] et al. focused on enhancing PBF-LB/M efficiency in AlSi10 Mg components while maintaining high-quality standards. Their investigation into process parameters found an optimal balance between part quality and productivity through the use of a high scan speed paired with a low hatch distance [153]. Similarly, [PERSON] et al. analyzed the impact of laser power and scanning speed on the microstructure and mechanical properties of AlSi7 Mg0.6, demonstrating that selecting mid-range laser power and scan speed within the optimal processing window enables the production of components with a refined microstructure and minimal defects [154]. The same outcomes were found by [PERSON] et al., who investigated strategies to increase the production rate of PBF-LB/M for AlSi10 Mg by optimizing critical process parameters. They found that the optimal combination of \(\
u\) and \(hd\) significantly reduced production time while preserving the material quality and performance [88]. In addition, they identified layer thickness as a key factor for improving process efficiency, especially for producing large-scale metal components [155]. In fact, in addition to the build time as defined by [PERSON]. et al. [150], it is important to consider machine times such as lowering the platform, passing the recoater to spread a layer, raising the platform, processing the CAD for the upcoming slice, and starting lasing. Increasing the layer thickness reduces the number of slices to be lasered, which decreases recoater passes and machine times.