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2025
Book Article
Title
NDE in Additive Manufacturing of Ceramic Components by LSP and OCT
Abstract
Additive manufacturing of ceramic green bodies is a new manufacturing, or more precisely a shaping technology for ceramic components. Any additive shaping technology is embedded in the established manufacturing chain of structural ceramic components. A key advantage of additive methods is the flexibility in low-volume manufacturing. The quality management for these parts is of high importance and requires new approaches beyond statistical sampling.
Optical methods are perfectly suited to be used in ceramics manufacturing as they are fast, versatile, and non-contacting. However, they must be adopted to the specifics of any process. The methods presented here are methods used within an additive manufacturing device focused on various specific shaping technologies in development.
Laser Speckle Photometry (LSP) is an optical nondestructive testing method. It is based on the dynamic analysis of time-resolved speckle patterns that are generated by an external excitation. In this chapter, we will present two investigation categories using the LSP technique for lithography-based manufacturing (LCM), first - detection of surface defects caused by local failures by selective fill-up during the building up of layer; and second - the supervision of mixing of two components in uncured slurry (suspension) or already cured multimaterial. In a second part, the results of inline characterization of correct layering of drops and solidification during multimaterial 3D Printing (T3DP) are presented.
The Optical Coherence Tomography (OCT) method utilizes a low coherence light to illuminate the investigated sample. Depending on the optical properties of the sample, especially the translucency at the wavelengths used, the light can penetrate from couple hundreds of micrometers to couple of millimeters into the sample. Presence of inclusions, pores, defects, or delaminations will cause a partial or total backscattering of the light, which appears in the OCT signal. The OCT method was used to investigate ceramic structures printed in a Multi-Material Jetting (MMJ) and the Multi-Component Additive Manufacturing Process (CAMP) process. It was possible to visualize surface defects and extract quantitative geometrical information of the printed structures including the surface roughness. Also, material contrast for multicomponent samples including cross-contamination was visualized.
Optical methods are perfectly suited to be used in ceramics manufacturing as they are fast, versatile, and non-contacting. However, they must be adopted to the specifics of any process. The methods presented here are methods used within an additive manufacturing device focused on various specific shaping technologies in development.
Laser Speckle Photometry (LSP) is an optical nondestructive testing method. It is based on the dynamic analysis of time-resolved speckle patterns that are generated by an external excitation. In this chapter, we will present two investigation categories using the LSP technique for lithography-based manufacturing (LCM), first - detection of surface defects caused by local failures by selective fill-up during the building up of layer; and second - the supervision of mixing of two components in uncured slurry (suspension) or already cured multimaterial. In a second part, the results of inline characterization of correct layering of drops and solidification during multimaterial 3D Printing (T3DP) are presented.
The Optical Coherence Tomography (OCT) method utilizes a low coherence light to illuminate the investigated sample. Depending on the optical properties of the sample, especially the translucency at the wavelengths used, the light can penetrate from couple hundreds of micrometers to couple of millimeters into the sample. Presence of inclusions, pores, defects, or delaminations will cause a partial or total backscattering of the light, which appears in the OCT signal. The OCT method was used to investigate ceramic structures printed in a Multi-Material Jetting (MMJ) and the Multi-Component Additive Manufacturing Process (CAMP) process. It was possible to visualize surface defects and extract quantitative geometrical information of the printed structures including the surface roughness. Also, material contrast for multicomponent samples including cross-contamination was visualized.