Time-dependent behaviour of photosensitive resins in mSLA technology

Abstract

Vat photopolymerization is an Additive Manufacturing (AM) technology that enables the production of dimensionally accurate components. Due to its accuracy, this technology has led to the development of various sub-types, each with different methods of introducing UV light to the liquid resin in the vat. UV light can be introduced through a mirror system (SLA), a projector (DLP), or an LCD screen that acts as a photomask over a projector’s light, allowing for the curing of the entire layer in one pass (MSLA). The material of interest in this study is a standard translucent resin used in MSLA, with a UV light wavelength of 405 nm. Previous extensive mechanical characterization of this material has shown a high dependence on the final component properties on layer thickness and curing times. The objective of this research is to analyse the time-dependent behaviour of these materials. Specifically, closed-loops compression tests have been conducted, subjecting the material to loading and unloading sequences at strain levels of 5 and 25 %. To clarify, a strain level of 5 % falls within the elastic region of the material, while a strain level of 25 % is considerably within the plastic region. Various testing speeds were applied, namely 1, 5, 10, 25, and 100 mm/min. The influence of testing speed on the materials’ energy absorption capacity is evident. The highest difference is observed between 10 and 25 mm/min, indicating that the material’s ability to store energy is significantly reduced after a testing speed of 10 mm/min.