cfaed Seminar Series

Volumetric additive manufacturing is defined as producing the entire volume of a component or structure simultaneously — rather than by layering — and has been envisioned as a possible way to increase the speed of polymeric additive manufacturing. Until recently, however, no practicable technique existed for creating arbitrary 3D geometries volumetrically. Computed Axial Lithography (CAL) offers a way to address this need. CAL essentially reverses the principles of computed tomography (widely used in imaging, but not previously in fabrication) to synthesize a three-dimensionally controlled illumination dose within a volume of photocurable resin. The photosensitive volume rotates steadily while synchronized patterns of light are projected perpendicular to the axis of rotation. In this way, the cumulative light dose in the material can be controlled in 3D, and where the dose exceeds a threshold, the resin solidifies and the part is formed.

The CAL printing technique has several advantages. Because the component being printed does not move relative to the resin during printing, the printing speed is not limited by resin flow effects, as it can be in layer-by-layer photopolymerization-based printing. The absence of relative motion also allows highly viscous resins or even solid gels to be used as the starting material, so that a wider range of mechanical properties can be achieved in printed components. Because layers are not used in CAL, the surfaces of printed objects are very smooth, which may open up new applications such as custom optical components. Additionally, it is possible to print objects around pre-existing solid objects that could have been made using a different material or process. This ‘overprinting’ capability suggests applications in mass-customization for end users.

I will discuss current and future research directions for CAL, in particular the prospects for scaling up the sizes of printed components (from the current 5–10 cm) or scaling down the minimum achievable feature sizes to the microscale. Some of the ongoing engineering challenges, including resin formulation requirements and projection algorithm needs, will be discussed. Finally, I will discuss application areas that may take particular advantage of CAL’s properties.