3D printing or additive manufacturing is the process for building complex geometries via successive addition of materials based on a digital model.&nbsp;However, the traditional 3D printing processes employing planar-layer printing strategy have rather limited flexibility in customization and multi-materials integration. Originally developed for the sole purpose of rapid prototyping, the planar-layer printing process slices the digital models along the z-axis to generate a set of horizontal build layers in x-y plane. Those layers are sequentially stacked from bottom-up to create the physical replica of the digital model. After more than three decades, this standard procedure remains the would-be choice in most of the commercial 3D printers possessing 3-Degree of freedom (DOF) Cartesian motion. Despite its popularity, the limited 1-DOF stage motion along z-axis imposes serious constraints in 3D printing complex geometries. Recognizing how multi-axis machines are capable of producing freeform geometries with better quality and efficiency as compared to the 3-axis machines, there is a growing interest in exploring the new slicing and printing strategy beyond the 3-DOF Cartesian motion. Methods that employed high-DOF stage motion have also investigated in enabling conformal 3D printing on non-planar surfaces and support-free 3D printing. Recently reported computed axial lithography (CAL) method prints entire complex objects via angular accumulation of dynamically evolving light pattern in a cylindric coordinate system. All these methods demonstrated the ability to handle complex geometries with improved speed and surface finishing. Inspired by these most recent studies, we went a step further by allowing freeform manipulation of each build layer during the layered manufacturing process.&nbsp;We show here untethering the build layer fabrication from unidirectional stage motion unlocks the means to reconstitute the 3D objects with added manufacturability such as custom design transformations, conformal geometry, and multi-material integration. The newfound fabrication flexibility allows us to&nbsp;executes full degree-of-freedom (DOF) transformation (translating, rotating, and scaling) of each individual building layer while utilizing continuous fabrication techniques. Transforming individual building layers within the sequential layered manufacturing process enables dynamic transformation of the 3D printed parts on-the-fly, eliminating the time-consuming redesign steps. Preserving the locality of the transformation to each layer further enables the discrete conformal transformation, allowing objects such as vascular scaffolds to be optimally fabricated to properly fit within specific patient anatomy obtained from the Magnetic Resonance Imaging (MRI) measurements.&nbsp;The manufacturability of the 3D printing process is further augmented with the use of the high-precision 6-axis robotic arm. It allows us to perform manufacturing tasks other than 3D printing, such as rinsing the samples mid-printing process.&nbsp;&nbsp;Finally, exploiting the freedom to control the orientation of each individual building layer, we further establish multi-materials, multi-axis 3D printing capability for integrating functional modules made of dissimilar materials in 3D printed devices. This final capability we demonstrate through 3D printing a soft pneumatic gripper via heterogenous integration of rigid base and soft actuating limbs.&nbsp;Although the reported method primarily focusing on the continuous stereolithography process, the underlying principle can be applied to other 3D printing process, with the potential to ease the burden towards the envisioned multi-process 3D printing.

Conformal Geometry and Multi-Material Additive Manufacturing Through Freeform Transformation of Building Layers

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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