Photopolymer Quality Measurement for SLA 3D Printing Using EIS

Additive Manufacturing (AM), and particularly 3D printing, plays a pivotal role in various domains of prototype and functional part production. This paper concentrates on photopolymers as the foundational material utilized in 3D printing via StereoLithogrAphy (SLA). A prevalent issue within AM is ensuring the base material achieves the correct form and possesses the desired properties. Photopolymers, primarily composed of oligomers, monomers, and photoinitiators, can exhibit drastically altered properties of the resin and consequently, the final printed material depending on the quantity and type of constituents used. Furthermore, the base material is subject to aging, which detrimentally impacts its properties and may ultimately result in defective prints. By assessing the electrochemical properties of the base material through Electrochemical Impedance Spectroscopy (EIS), it is feasible to measure and appraise these alterations. The analysis of three samples at varying stages of degradation reveals that the evaporation of the photoinitiator within the resin leads to the deterioration of the photopolymer. This degradation increases the likelihood of print failure, poses a heightened risk of incomplete polymerization, and enhances the potential for material delamination. Given the non-destructive characteristic of the EIS technique and the observable variances in the data, EIS can be affirmed as an effective method for monitoring the quality of resin.