Abstract
In the present paper, the degree of cure-dependent viscoelastic properties of a commercial photopolymer resin (Loctite^{textregistered } 3D 3830) used in digital light processing (DLP) 3D printing are investigated experimentally and described by suitable model equations. To do this, tests are carried out both on the liquid resin and printed specimens under various conditions. The experimental methods include photo-DSC, UV rheometry, and dynamic mechanical analysis. A commercial digital light processing (DLP) printer (Loctite^{textregistered } EQ PR10.1) is used for the printing of the samples. Model equations are proposed to describe the behavior of the material during and after the printing process. For the representation of the degree of cure depending on temperature and light intensity, the one-dimensional differential equation proposed in a previous paper is extended to capture a temperature-dependent threshold value. The change of the viscoelastic properties during crosslinking is captured macroscopically by time-temperature and time-cure superposition principles. The parameters of the model equations are identified using nonlinear optimization algorithms. A good representation of the experimental data is achieved by the proposed model equations. The findings of this paper help users in additive manufacturing of photopolymers to predict the material properties depending on the degree of cure and temperature of printed components.
Highlights
During the last 3 decades, additive manufacturing (AM) processes for polymers have undergone rapid development from prototyping to small- and medium-sized production
Photopolymer resins are used in additive manufacturing processes like digital light processing (DLP) and stereolithography (SLA)
The liquid resin is cured by UV irradiation and built up layerwise to the desired geometry
Summary
During the last 3 decades, additive manufacturing (AM) processes for polymers have undergone rapid development from prototyping to small- and medium-sized production. Due to the general increase of research activities in the field of additive manufacturing, the experimental characterization and description of the material behavior of photopolymer resins with suitable model equations have been of high relevance. These investigations include all steps of the entire AM process chain:. It consists of a full HD (1920 x 1080 pixels) projector, which emits UV radiation at a wavelength of 405 nm by an LED This open system enables the usage of all third-party photopolymer resins that cure at a wavelength of 405 nm as well as the adjustment of all relevant process parameters (layer thickness, exposure time, irradiance, etc.). The authors have discovered that a resin tray with integrated temperature control enables a better processing of highly viscous photopolymer resins
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