## 2 Process Flow and Performance Indicators of Binder Jetting 3D Printing
### Process Flow and Pre-Printing Parameter Selection for Binder Jetting of Silicon Carbide Components
Therefore, when pursuing enhanced surface detail resolution through particle size reduction, it is critical to maintain a minimum particle size threshold of 5 \(\upmu\)m.  
On the other hand, regarding the selection of binder systems, apart from some special cases where the binder is a type of solvent that facilitates particle fusion, mainly for polymers but also applied in magnesium powder studies [35], there are two primary binder methods: in-liquid binding and in-bed binding. Additionally, the in-bed binding mechanism is divided into dry pre-mixing and wet pre-mixing. In-liquid binding involves adding binder material to the printing solution and then spraying this binder solution onto the powder bed to adhere particles using the inherent viscosity of the solution [36]. Dry  
Figure 4: Schematic diagrams of SiC printed by BJ, PRIP, and LSI post-processes: (**a**) green part achieved by BJ; (**b–d**) SiC/C preforms achieved by PRIP; (**e**) Si-SiC composites achieved by LSI. Cited from [17]. pre-mixing [37] involves using a grinder or ball mill to pre-mix ceramic and solid binder, followed by spraying a print liquid (usually water-based) onto the powder bed to react with the solid binder, creating a viscosity that binds the SiC particles together. Wet pre-mixing involves dissolving binder material in a solvent (e.g., water), then adding ceramic material to obtain a mixed slurry. The slurry is then spray-dried [38] or freeze-dried [39] and sieved, with a binding mechanism consistent with dry pre-mixing. Wet pre-mixing relies on the binder's ability to evenly coat the powder, but, due to the poor hydrophilicity of SiC [40], the powder tends to agglomerate due to localized binder enrichment, potentially leading to reduced print quality; thus, the BJ manufacturing process for SiC powder opts for either liquid spraying or dry pre-mixing. Based on an extensive literature review, [PERSON] et al. [41] systematically summarized the distribution of binder types employed in BJ 3D printing for ceramic component fabrication, with jetting in-place accounting for 51%, dry pre-mixing for 12%, wet pre-mixing for 25%, and not-specified types constituting the remaining 12%. The requirements for print quality, sintering density, and mechanical properties of the final parts, along with their industrial feasibility, are the main considerations for selecting a binder. This necessitates a thorough understanding of the printing effects, advantages, and disadvantages of different binders, as well as their applicable scenarios. Table 2 summarizes the advantages, disadvantages, and applicable scenarios of choosing in-liquid binder spraying versus dry pre-mixing of solid binders. It is worth mentioning that, in the BJ 3D printing green parts formation process, the printhead is the core of the system, and its performance directly affects the quality of the final product. The printheads in BJ 3D printing equipment are mostly piezoelectric printheads, which control the ejection of droplets by driving deformation of piezoelectric crystals with voltage, as shown in the schematic diagram in Figure 5.  
Print resolution and frequency are important indicators of piezoelectric printhead performance, where resolution determines the precision of printed details and frequency affects printing speed and efficiency. Increasing the number of printheads can enhance print quality and speed, but also add complexity to maintenance, especially in high-precision applications, where the failure of any printhead can impact the printing results. Therefore, the selection of printheads must comprehensively consider efficiency and cost to fully leverage the advantages of BJ 3D printing technology. Table 3 summarizes the equipment parameters of mainstream printhead brands.