Lawrence Livermore National Laboratory



Computed Axial Lithography (CAL) for 3D Additive Manufacturing

Background

Additive manufacturing (AM) fabrication methods are proliferating rapidly, with photopolymer-based approaches comprising some of the most prominent methods. These stereolithographic techniques provide a useful balance of resolution, build speed, process control, and capital cost (system metrics that typically must be traded off one against another). Resolving the speed limitations, surface roughness (stair-step artifacts), and requirements for support structures would provide the next major steps forward in the progress of these technologies.


Description

LLNL has developed a system and method that accomplishes volumetric fabrication by applying computed tomography (CT) techniques in reverse, fabricating structures by exposing a photopolymer resin volume from multiple angles, updating the light field at each angle. The necessary light fields are spatially and/or temporally multiplexed, such that their summed energy dose in a target resin volume crosslinks the resin into a user-defined geometry. These light-fields may be static or dynamic and may be generated by a spatial light modulator (SLM) that controls either the phase or the amplitude of a light field (or both) to provide the necessary intensity distribution.


Advantages

The LLNL approach surpasses recently-reported volumetric aperiodic three-dimensional (3D) structure fabrication using holographic light fields in its geometric flexibility. Similarly, the inherently volume-based approach of the present invention provides an order-of-magnitude improvement in fabrication speed over conventional layer-by-layer "2 1/2D" printing techniques. Finally, the surface roughness problems imposed by layer-by-layer fabrication are substantially reduced if not removed entirely.

Past and current use has included improvement to photopolymer-based additive manufacturing:

  1. Faster part generation
  2. Improved surface quality, no stair step artifacts from layering
  3. Reduction of geometric constraints that arise from 2D layer slicing, simplified post-processing

Potential Applications

  • AM generated optics with high quality surface finish
  • Hollow or overhanging structures
  • Large dynamic range mesoscale AM structures
  • Printing/fabrication on a previously fabricated 3D structure immersed in the resin
  • Processing very soft, flexible or brittle polymers and geometrically delicate/fragile structures (as there is no relative structure/fluid motion during printing).


Development Status

LLNL has filed a U.S. Patent Application No. 15/593,947; LLNL internal case number (IL-13182).


ID

37518


Email
mempin1@llnl.gov