Abstract

Subject of study. A digital holographic system for layer-by-layer control of component quality in additive manufacturing able to determine the size and depth of defects on the surface of each layer was investigated. Method. The digital holographic system for layer-by-layer control of component quality in additive manufacturing operates based on a two-wavelength holographic interferometry method. The digital holographic system is based on a Michelson interferometer. The considered method involves recording holograms of the surface of each component layer at two adjacent wavelengths. As a result of hologram reconstruction, the complex amplitudes of the object wave in the reconstruction plane are determined, which, in turn, define the phases of the waves and their difference. The wave phase difference allows the depth of the defect on the component layer surface to be determined. A tunable diode laser and camera based on a CCD matrix are used as the radiation source and detector, respectively. Main results. The results of the investigation of the surfaces of additively manufactured components using the two-wavelength holographic interferometry method are presented. The recognition of large irregularities is possible through expansion of the phase pattern. The detection of surface defects with the size of 25 µm is demonstrated. The reconstructed surface of a component manufactured by laser sintering of successive layers using the M250 additive setup for selective laser sintering and the reconstructed surface of a millimeter-scale macroscopic object are presented. Practical significance. The possible use of the digital holographic system for component quality control in industrial settings, including those applying additive technologies, is demonstrated. The component quality criterion is the absence of defects (cavities or protrusions) with size larger than 25 µm.

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