The important role of industrial CT in additive manufacturing

Non-destructive testing (NDT) plays a crucial and increasingly prominent role in additive manufacturing (commonly known as 3D printing), and is considered key to overcoming technological bottlenecks and achieving large-scale application in high-value sectors.

1. Core Role: Ensuring the Intrinsic Quality and Reliability of "Printed Parts"

Additive manufacturing creates parts by layer-by-layer deposition. This process can introduce unique defects that are difficult to detect externally but have a significant impact on performance. The core role of NDT is to identify these hidden problems:

Porosity and Incomplete Fusion: Incomplete fusion may occur between layers or along the scanning path due to insufficient energy, or gas trapping may form voids, which can severely reduce the mechanical properties of the part (especially fatigue strength).

Cracks: Residual stress from rapid heating and cooling can lead to micro-cracks, especially in materials such as high-temperature alloys.

Inclusions: Foreign matter or contamination may be mixed into the powder, forming inclusions during the printing process.

Dimensional Deviations and Morphology Issues: Residual support structures, abnormal surface roughness, and the unobstructed flow of complex internal channels, etc.

2. Application Phase: From Process Monitoring to Finished Product Acceptance

Non-destructive testing (NDT) is applied throughout additive manufacturing, forming a comprehensive quality assurance system across the entire product lifecycle:

Online/In-Process Monitoring: This is the cutting-edge field of NDT in additive manufacturing. By integrating high-speed cameras, thermal imagers, photodiodes, or laser ultrasonic sensors within the printing chamber, the morphology, size, temperature field, and light radiation signals of the molten pool are monitored in real time. Purpose: To detect process anomalies in real time (such as energy fluctuations or uneven powder distribution) and immediately provide feedback to adjust process parameters, achieving "detection and correction," eliminating defects at the source. Simultaneously, a "digital twin" and "birth record" are established for each part.

Post-Processing/Finished Product Inspection: After the part is printed, the substrate is removed and necessary heat treatments (such as stress-relief annealing and hot isostatic pressing) are performed. Rigorous NDT must then be conducted to confirm its final quality. Purpose: To serve as the final quality certificate before shipment or installation, ensuring that the part meets design standards and customer requirements.

3. Commonly Used Non-Destructive Testing Methods and Their Characteristics

For the complex structures and defects of additively manufactured parts, Industrial Computed Tomography (Industrial CT):

This is currently one of the most powerful and ideal methods for inspecting additively manufactured parts. It can generate a complete 3D model of the part's interior, clearly showing the location and size of pores and cracks, and accurately measuring the dimensional accuracy of complex internal flow channels and thin-walled structures, achieving "non-destructive sectioning." It is widely used in aerospace, medical devices (such as implants), and other fields with extremely high internal quality requirements.

X-ray Inspection (DR/CR): Faster and lower cost than industrial CT, suitable for rapid 2D projection inspection of known high-risk areas. For complex structures, defects are easily obscured due to structural overlap, lacking 3D information.

From a passive "quality screening tool" to a proactive "process optimization and quality assurance partner." It is not only used to remove waste products, but more importantly, through online monitoring and refined offline analysis, it guides and optimizes printing process parameters, promoting additive manufacturing from "manufacturing is possible" to "reliable manufacturing" and "high-quality manufacturing", ultimately enabling it to gain trust and widespread application in cutting-edge fields related to life safety (such as aero engines and human implants).