2.5D printing is a technology which creates surface relief by superimposing successive layers of inks. The question of the characterization of heights obtained with this technique brings us to consider new metrics and mathematical ways to represent the influence of diverse printing parameters on the obtained relief, possibly used to compensate the defaults of the system. Our method takes over the classical Modulation Transfer Function (MTF) approach and adapts it to a vertical modulation instead of considering the (x, y) plane, introducing then a Height Modulation Transfer Function (HMTF). Characterization charts are composed of lines patterns printed at different heights, frequencies and droplet levels. Prints are scanned with a chromatic confocal sensor and resulting topographies are analyzed to extract the HMTF. By analogy with traditional MTF methods, results – consisting of the measurement of the deviation between the digital input and the analog output – allow to evaluate the quality of our printer and to compensate it by setting up a retro-action loop. The method, here presented in the case of the 2.5D printing prototype, can be extended to regular 3D printing techniques.
Marine Page, Gaël Obein, Clotilde Boust, Annick Razet, "Adapted Modulation Transfer Function Method for Characterization and Improvement of 3D printed surfaces" in Proc. IS&T Int’l. Symp. on Electronic Imaging: Material Appearance, 2017, pp 92 - 100, https://doi.org/10.2352/ISSN.2470-1173.2017.8.MAAP-279