## 3 Quality Control of Silicon Carbide Printed Part Formation
### Detection and Assessment Techniques  
In the BJ 3D printing process, it is crucial to conduct performance testing on both green parts and final components after densification post-processing--the former evaluates forming quality and optimizes the debinding process, while the latter validates the material's final performance and detects densification-induced defects. Their combination establishes a closed-loop quality control system throughout the entire manufacturing chain, providing dual assurance for process optimization and product reliability. Geometric and dimensional accuracy testing of green parts is a critical step in evaluating whether the BJ 3D printing process meets manufacturing performance requirements. The testing data serves as primary reference parameters for guiding both accuracy compensation design in post-processing stages and printing process optimization. For green parts, coordinate measuring machines (CMMs) generate detailed surface profiles and three-dimensional morphology data through scanning and point measurements, enabling calculation of surface roughness parameters [173]. CMMs provide sub-micrometer measurement accuracy and resolution, allowing high-precision measurements over large areas, making them suitable for complex geometries and large-sized components [174]. However, SiC ceramic components are characterized by high hardness and brittleness, and, during CMM inspection, the probe makes direct physical contact with the component's surface, which may cause minor damage to fragile or delicate surfaces. Additionally, the size of the probe limits the minimum feature size that can be measured, which results in CMMs being insufficient for accurately measuring small surface details and complex microstructures of SiC ceramic printed parts. The coordinate measuring machine industry has numerous brands, including Sweden's Serein, Germany's AEH, America's Leader, Germany's WENZEL, Japan's Mitutoyo, and China's Aviation Precision 303, all of which hold significant advantages in brand image, product quality, innovative technology, and marketing strategies. Among the many coordinate measuring machine manufacturers, FARO is a globally recognized supplier of 3D technology, widely applied in the precision inspection of BJ 3D printing, dedicated to providing mature and comprehensive 3D measurement, imaging, and implementation solutions, with strong research and production capabilities and multiple international patents. Its products are mainly used in formation quality control and inspection, product design and engineering, layout design, and projection, enjoying a high level of recognition and reputation in the computer-aided measurement equipment industry, and its accuracy measurement schematic is shown in Figure 18.  
From a cost perspective, coordinate measuring machines (CMMs) are more prevalent in binder jetting 3D printing inspection technologies when meeting the required printing accuracy specifications. In contrast to the point-measurement approach of CMMs, optical methods analyze geometric features and dimensional measurements by performing multi-directional scanning of surface profiles [175]. This non-contact characteristic ensures the absence of physical damage to the surfaces of SiC ceramic printed components, consequently enabling their widespread application in the performance evaluation of post-densification final parts. These optical methodologies will be comprehensively reviewed in the subsequent nondestructive testing section. Mechanical and thermal property testing of green parts  
Figure 18: FARO measurement arm measuring print accuracy [133]. Mechanical and thermophysical property testing constitutes a critical evaluation for green parts, requiring multiple test protocols to comply with national assessment standards. Geometric and dimensional accuracy alone cannot serve as the sole parameter for determining printed part quality.