Manufacturing Capability of Three-Dimensional Printed Stereolithography Parts for Impact Applications

Abstract

Three-dimensional (3D) printing with high-resolution stereolithography (SLA) has grown in popularity for creating personalized medical devices. 3D printing is now starting to expand to weight-bearing components, e.g., prosthetic feet, as data on the dynamic properties impact and fatigue is published in the literature. The next step toward using 3D printing in impact applications is to assess the capability of the high-resolution SLA process to manufacture components of uniform impact resistance. Because impact testing is destructive, a surrogate measure to check a part's viability for resisting an impact load also needs to be established. Thirteen notched Izod specimens were printed on a Form2 SLA printer using the manufacturer's photocurable resins: clear, flexible, durable, and draft. Once all the specimens were printed, washed in isopropyl alcohol, and cured with ultraviolet light, the impact resistance was quantified using a pendulum impact tester in a notched Izod configuration. Then, the hardness of the specimens was quantified using a Shore durometer. The process capability indices of the impact resistance for the various polymers were 0.11 (clear), 0.43 (flexible), 0.65 (durable), and 1.07 (draft). Impact resistance and Shore durometer were only correlated for the flexible resin with a Spearman coefficient of r = 0.738, p < 0.005. Since the process capability index was so variable across materials, 3D printing with SLA polymers is not a viable manufacturing process for creating parts of consistent impact resistance. The current technology would lead to too many rejected parts.