Abstract
Material shrinkage commonly occurs in additive manufacturing and compromises the fabrication quality by causing unwanted distortions or residual stresses in fabricated parts. Even though it is known that the resulting deformations and stresses are highly dependent on the writing trajectory, no effective strategy for choosing suitable trajectories has been reported to date. Here, we present a path to achieve this goal in direct laser writing, an additive manufacturing method based on photopolymerization that commonly suffers from strong shrinkage-induced effects. First, we introduce a method for measuring the shrinkage of distinct direct laser written lines. We then introduce a semi-empirical numerical model to capture the interplay of sequentially polymerized material and the resulting macroscopic effects. Finally, we implement an artificial neural network to evaluate given laser trajectories in terms of the resulting part quality. The presented approach proves feasibility of using artificial neural networks to assess the quality of 3D printing trajectories and thereby demonstrates a potential route for reducing the impact of material shrinkage on 3D printed parts.
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Notes
We insert a 5-s break in the DLW process after writing of the distinct lines.
We write the sheets freely immersed in the liquid photoresist. After a 5-s break, we add lines at the four corners that connect the sheets to a surrounding frame without influencing the occurred deformations.
We tested networks with 10 linearly varied regularization parameters in the range 0 ≤ λ ≤ 1.
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Acknowledgments
We would like to thank Jan Rys and Matthew Hunt for their kind help with SEM.
Funding
This work was partially funded by the Swiss National Science Foundation through grant “MechNanoTruss-Mechanical response of polymer nanotruss scaffolds” (No. 164375). The experiments were conducted with support from the Kavli Nanoscience Institute at Caltech.
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Bauhofer, A., Daraio, C. Neural networks for trajectory evaluation in direct laser writing. Int J Adv Manuf Technol 107, 2563–2577 (2020). https://doi.org/10.1007/s00170-020-05086-3
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DOI: https://doi.org/10.1007/s00170-020-05086-3