LLNL’s breakthrough Volumetric Additive Manufacturing (VAM) technology takes computed tomography (CT) “views” of 3D objects from multiple angles, and projects these images into a photosensitive resin. The resin cures at points where the accumulated, absorbed light energy exceeds the gel thresholds, and when the remaining liquid resin is drained, it produces 3D objects within seconds or minutes, much faster than traditional layer-by-layer 3D printing techniques. Since this revolutionary manufacturing process can 3D print components in one step, real-time monitoring of the process is critical to increase reliability and to avoid product waste. Conventional monitoring relies on high refractive index or scattering property change of resin materials upon polymerization. However, for resins with low refractive index change, these conventional imaging methods fail due to low contrast. There is a need for imaging methods that can visualize VAM processes of low refractive index-changing materials.
The approach is to use quantitative phase imaging (QPI) using a common-path phase-shifting interferometry technique. A sequence of four phase shifts with an increment of π/2 between unscattered reference beam and scattered sample beam are imparted by a spatial light modulator. A quantitative phase image is retrieved from four raw intensity images. QPI is a highly sensitive imaging method that provides high contrast image even for even with slight refractive index changes. Phase contrast imaging is also used to monitor the onset and progression of the VAM process.
Image Caption: Optical schematic of VAM Quantitative Phase Imaging (QPI) system
Dongping Terrel-Perez, Johanna Schwartz, Martin De Beer, "Quantitative phase imaging for volumetric additive manufacturing," Proc. SPIE PC12898, Advanced Fabrication Technologies for Micro/Nano Optics and Photonics XVII, PC128980K (13 March 2024); https://doi.org/10.1117/12.3008523
Current stage of technology development: TRL 3
LLNL has filed for patent protection on this invention.
- Value Proposition: Better qualification and certification of VAM printed parts
- Real-time in situ monitoring of the VAM process
- Possible application to other vat polymerization AM processes
- Volumetric Additive Manufacturing
- Potentially other vat polymerization processes
