Characterization techniques for evaluation of micro scale vat photopolymerization-based additive manufacturing

Vat photopolymerization-based Additive Manufacturing (VPAM) is a process in which a liquid polymer resin is exposed to UV light and cross-linked creating a tough structure. This technique allows to produce highly complex parts and has found its application in many fields e.g. hearing-aid components, dentistry and jewellery. The potential of VPAM makes it possible to be used in more advanced and demanding applications such as robotics, functional surfaces and soft tooling, just to name a few. These applications require manufacturing of features in micro scale with defined tolerances, thus, the current state-of-the-art calls for high precision and stability of the process as well as reliable characterisation techniques. This paper presents the efficiency of selected characterisation methods together with comparison between the influence of layer thickness and irradiance on the degree of curing as well as the dimensional and weight stability. By applying spectroscopic methods and geometrical measurements it was found that the two selected parameters have contradicting effect on the evaluated features. The results showed that the process is the most stable for two sets of process parameters: irradiance of 0.91 mW/cm² with layer thickness of 1 μm and 1 mW/cm2 with layer thickness of 5 μm. The degree of curing was found to be higher for high light irradiance, with the thickness found to be an insignificant factor.