Graduate Thesis Or Dissertation
Fundamental Developments in Volumetric Additive Manufacturing Public Deposited
The relatively new field of Volumetric Additive Manufacturing (VAM) performs printing intoa fixed volume of resin in a single lithographic step. This has multiple advantages over multistep additive manufacturing methods. Notably, non-contiguous parts become possible, layering effects are eliminated, print speeds are improved by orders of magnitude, and the lack of material movement mid-print enables high-viscosity or even solid resins, opening the doors to a host of new material properties. However, prior to this work, VAM suffered from multiple limitations that both restricted its scope of application and prevented its practical use as a manufacturing technique.
Firstly, there was a lack of tomographic calculation techniques to provide sufficient opticaldose control for a variety of VAM applications. From printing 3D parts without shape error, to controlling grayscale optical dose for e.g. printing optics or functionally graded materials, control over dose is critical in VAM. We present a simple and effective approach to VAM image computation that significantly improves over prior methods. We demonstrate the flexibility of the approach by extending it to include material response models, optical models including beam shape and occlusions for overprinting, as well as to the problem of controlling grayscale dose throughout a print.
Secondly, VAM was limited to printing into small cylindrical sample packages. We present atomosynthetic VAM printing geometry that allows for printing into flat surfaces. This lends itself to applications such as the manufacturing of flat microfluidic chips, printing into well plates, or any other printing application requiring beam access through a surface. It further allows for the patterning of arbitrarily large sheets. We discuss theory and image computation for this printing geometry, and we present experimental proof of concept prints.
Thirdly, VAM ubiquitously suffered from large striations – similar in appearance to layering,and on the order of print feature size – impacting the homogeneity and shape-accuracy of printed parts, and presenting a significant cosmetic defect. We present evidence that the material nonlinearity upon which VAM relies also drives striations via a self-writing waveguide (SWW) effect. We demonstrate a simple and effective method of dramatically reducing striations via a latent-cure, flood-exposure step. We additionally show this to drastically shorten the period from initial gelation to print completion. This mitigates the problem of partial-print sinking in low power or low viscosity prints, thus further expanding resin options and increasing the efficacy of low-cost VAM printers.
We discuss the fundamentals of VAM optics and materials, and the constraints on both thatinform the design approach of VAM printers and resins. We present measurement methods for material selection, and we detail the design and alignment of a particular printer.
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