Effect of post-curing on the tensile strength of castable wax material produced by SLA 3D printing

Abstract

This study examines in detail the impact of key post-curing parameters—temperature (39–80°C) and duration (11–140 min)—on the mechanical properties of castable wax resin V1 (a specialized material containing 20% wax). The material was fabricated using stereolithography (SLA) 3D printing, and the test specimens were prepared according to the ASTM D638–Type IV standard. Quantitative analysis (using response surface methodology) indicated that concurrent increases in post-curing temperature and duration result in a significant, statistically meaningful improvement in both maximum tensile strength and Young’s modulus. Specifically, the tensile strength increased from 12 MPa in the “Green State” up to 33.32 MPa (observed at 75°C – 120 min). Similarly, Young’s Modulus increased significantly from 220 MPa in the “Green State” up to 1155.26 MPa (observed at 60°C – 140 min). Conversely, the nominal strain at break decreases with increasing temperature. The strain at break decreased from 13% in the “Green State” to a minimum of 7.31% (at 60°C – 140 min), indicating that the material becomes harder but also more brittle. The study identified the optimal post-curing regime for achieving the highest mechanical performance of castable wax resin V1: a post-cure temperature of 80°C and a post-cure time of 140 min. The identification of these optimal parameters provides a solid scientific basis for optimizing the SLA additive manufacturing process. When applying the optimal regime (80°C and 140 min) in experimental jewelry casting, the results obtained were very positive. The resulting cast piece still reproduced the thinnest and most minor details, indicating that the casting pattern has high mechanical strength and resists external forces throughout the investment casting process without cracking or fracturing.