Conversion Mapping by Raman Microscopy and Impact of Slice Overlap in Additive Manufacturing

Improved materials designed specifically for 3D printing are required before the technology becomes ubiquitous; however, trial and error printing parameter development is hindering progress. We describe an innovative Raman data analysis method to map conversion through cross-sectioned 3D printed layers. The method alleviates two common complications present in Raman spectroscopy, varying baselines and normalization of spectra, resulting in high quality chemical maps showing the monomer to polymer conversion profile throughout a 3D printed part. The conversion profile is used to demonstrate the impact of "overlap"between slices (layer thickness) on the providing sufficient structural strength during printing while also maintaining resolution. A simple printing process using "infinite cure"to determine the layer thickness that can be cured to a sufficient level to become solid has been identified as a means to optimize photoinitiator and photoabsorber levels, exposure, and time.