Characterization of Shrinkage and Stresses in Large Area Maskless Photopolymerization

Large Area Maskless Photopolymerization (LAMP) is a high throughput direct digital manufacturing technology being developed for producing ceramic investment casting molds. Polymerization shrinkage and accompanying stresses developed during photopolymerization of ceramic particle-loaded resins in LAMP can cause deviations from the desired geometry. The extent of deviations depends on photoinitiator concentration, filler loading, degree of monomer conversion and operating parameters such as energy dose. An understanding of shrinkage and stresses built up in the part can assist in developing source geometry compensation algorithms and exposure strategies to alleviate these effects. Real-time Fourier Transform Infrared Spectroscopy (RTFTIR) operated in Attenuated Total Reflectance (ATR) mode is used to characterize the three-dimensional shrinkage stresses. This work is sponsored by DARPA Grant HR0011-08-1-0075.