## 3 Quality Control of Silicon Carbide Printed Part Formation
### The Impact and Control of Key Printing Parameters on Green Part Formation Quality
#### 3.1.3 Elimination of the Stair-Step Effect
Research and development regarding adaptive slicing algorithms have expanded the slicing process for handling complex-shaped printed models, but currently, adaptive slicing strategies are still largely in the research interest phase and are seldom implemented on BJ 3D printers. Figure 14: Thin-layer slicing versus thick-layer slicing printed parts exhibiting the stair-step effect on the surface [120]. The high research and development costs are considered the main reason for the lack of widespread adoption of adaptive slicing. However, from the essence of the BJ 3D printing process of green body formation, [PERSON] et al. [126] proposed a new perspective, that spraying the same volume of binder on layers of different thicknesses will inevitably lead to accuracy issues in the printed parts. As shown in Figure 15, the bonding and reactions between binder droplets and the powder or substances within the powder are crucial for the binder green body. Insufficient binder spray volume can lead to inadequate adhesion between layers (as shown in Figure 15c), while excessive binder spray volume can result in unnecessary powder bonding, causing shape accuracy issues (as shown in Figure 15a). Thus, it is crucial to apply a suitable amount binder during the printing process (as shown in Figure 15b). As demonstrated in the research report by [PERSON] et al. [127] on the effects of binder content on the formability and performance of polymethyl methacrylate (PMMA), it is necessary for the binder content to be greater than 10% when 3D printing parts from PMMA. When the binder content exceeds 40%, it is prone to causing shape deformation. This indicates that excessive binder can lead to over-spreading, resulting in reduced surface smoothness and poor dimensional accuracy, and the bonding of previous layers may also be affected by the excess binder. Taturation of the binder is used to describe the percentage of fluid-filled pores when the binder permeates downward into the powder bed [128]. Currently, the saturation of the binder is used to measure the volume content of the binder. Undersaturation (<1) indicates that the powder pores are not fully filled, which highlights the concern of insufficient bonding leading to the \"layer shifting\" phenomenon, as well as the potential for high levels of voids and porosity that may occur after the burnout and sintering steps. In contrast, oversaturation (>1) indicates that the powder pores are filled with binder, and that there is a phenomenon of binder overflow, which is likely to cause additional powder particles to adhere to the surface of the 3D-printed parts, leading to increased surface roughness and dimensional errors [118; 129]. The lack of adaptive binder control strategies for different adaptive layer thicknesses is a significant factor affecting the effectiveness of adaptive algorithms in controlling print quality, and it is also a major obstacle to their application in practical printing processes. [PERSON], in his latest review on droplet jetting research [130], pointed out that the key to controlling forming accuracy is how to eject droplets of any volume. He further clarified the main issue that current research should focus on, which is to study the relationship between binder spray volume and formation accuracy based on the fundamental principles of micro-droplet jetting. Starting from the fundamental principles of micro-droplet jetting, research should examine the relationship between binder spray volume and formation accuracy at specific layer thicknesses. [PERSON] et al. [54] established a mechanical model of the MDI device's mechanical actuator based on the droplet generation process model at the printhead developed by [PERSON] [131] and [PERSON] [132], which considers the effect of the structural displacement field. They analyzed the relationship between the characteristics  
Figure 15: The effect of binder spray volume on printing results, based on [PERSON] et al. [47]. **(a)** In-sufficient binder jetting volume. **(b)** Optimal binder jetting volume.