Impact of beam shape on print accuracy in digital light processing additive manufacture

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Reid, Andrew and Windmill, James (2024) Impact of beam shape on print accuracy in digital light processing additive manufacture. 3D Printing and Additive Manufacturing, 11 (2). pp. 517-528. ISSN 2329-7670 (https://doi.org/10.1089/3dp.2022.0193)

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Abstract

Photopolymerization-based additive manufacturing requires selectively exposing a feedstock resin to ultraviolet (UV) light, which in digital light processing is achieved either using a digital micromirror device or a digital mask. The minimum tolerances and resolution for a multilayer process are separate for resolution through the Z-axis, looking through the thickness of a printed part, and resolution in the XY-axes, in the plane of the printed layer. The former depends wholly on the rate of attenuation of the incident UV light through the material relative to the mechanical motion of the build layer, while the latter is determined by a two-dimensional pattern of irradiance on the resin formed by the digital micromirror device or the digital mask. The size or the spacing of elements or pixels of this digital mask is frequently given by manufacturers as the “resolution” of the device, however, in practice the achievable resolution is first determined by the beam distribution from each pixel. The beam distribution is, as standard, modeled as a two-parameter Gaussian distribution but the key parameters of peak intensity and standard deviation of the beam are hidden to the user and difficult to measure directly. The ability of models based on the Gaussian distribution to correctly predict the polymerization of printed features in the microscale is also typically poor. In this study, we demonstrate an alternative model of beam distribution based on a heavy-tailed Lorentzian model, which is able to more accurately predict small build areas for both positive and negative features. We show a simple calibration method to derive the key space parameters of the beam distribution from measurements of a single-layer printed model. We propose that the standard Gaussian model is insufficient to accurately predict a print outcome as it neglects higher-order terms, such as beam skew and kurtosis, and in particular failing to account for the relatively heavy tails of the beam distribution. Our results demonstrate how the amendments to the beam distribution can avoid errors in microchannel formation, and better estimates of the true XY-axes resolution of the printer. The results can be used as the basis for voxel-based models of print solidification that allow software prediction of the photopolymerization process.

ORCID iDs

Reid, Andrew ORCID logoORCID: https://orcid.org/0000-0003-0511-4640 and Windmill, James ORCID logoORCID: https://orcid.org/0000-0003-4878-349X;
  • Item type:Article
    ID code:84358
    Dates:
    Date
    Event
    1 April 2024
    Published
    3 February 2023
    Published Online
    27 November 2022
    Accepted
    Notes:Copyright © 2023 Owner. This is the accepted version of the following article: Reid, A., & Windmill, J. (2023). Impact of beam shape on print accuracy in digital light processing additive manufacture. 3D Printing and Additive Manufacturing. https://doi.org/10.1089/3dp.2022.0193. This original submission version of the article may be used for non-commercial purposes in accordance with the Mary Ann Liebert, Inc., publishers' self-archiving terms and conditions.
    Subjects:Technology > Manufactures
    Department:Faculty of Engineering > Electronic and Electrical Engineering
    Depositing user: Pure Administrator
    Date deposited:22 Feb 2023 16:44
    Last modified:03 Dec 2024 01:24
    URI:https://strathprints.strath.ac.uk/id/eprint/84358
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