Optical properties of tilted surfaces in material jetting

Material jetting (MJT) is a promising additive manufacturing (AM) technique that offers high-quality appearance reproduction. Considering the limited selection of aesthetic materials available for MJT technology, a thorough optical analysis is required to determine their optimal application. This study focuses on the prominent appearance attributes in MJT and the role of texture variation due to different build orientations (BOs). For this purpose, tilted surfaces were manufactured in a direction ranging from 0 degrees to 90 degrees degrees at 15 degrees intervals. The spectral reflectance, absorbance, transmittance, color difference, gloss, haze, scattering, and texture of MJT objects with varying BOs were investigated. To illustrate the variation in visual appearance and texture of the studied surfaces, the optical properties were rendered to three-dimensional (3D) spherical models. Further, the interaction of the appearance of 3D printing interacts with the quality improvement of AM surfaces is discussed. The results indicated that BO significantly affected the surface texture and layer orientation, leading to variation in surface quality by impacting all studied appearance attributes. Furthermore, tilted MJT surfaces exhibited more variation in reflectance than transmittance. As a result of the Kendall rank correlation coefficient and principal component analysis (PCA), light transmittance through parts manufactured at BO 75 degrees showed the largest variation compared to 0 degrees. Regarding light reflectance, 60 degrees showed more variation among studied angles. The results of gloss, haze, and scattering studies revealed the significance of the measurement direction due to the role of microsurface normals in the surface texture.