Hot Lithography Vat Photopolymerisation 3D Printing: Vat Temperature vs. Mixture Design

Abstract

In the vat photopolymerisation 3D printing technique, the properties of the printed parts are highly dependent on the degree of conversion of the monomers. The mechanisms and advantages of vat photopolymerisation at elevated temperatures, or so called “hot lithography”, were investigated in this paper. Two types of photoresins, commercially used as highly accurate castable resins, with different structural and diluent monomers, were employed in this study. Samples were printed at 25 °C, 40 °C, and 55 °C. The results show that hot lithography can significantly enhance the mechanical and dimensional properties of the printed parts and is more effective when there is a diluent with a network Tg close to the print temperature. When processed at 55 °C, Mixture A, which contains a diluent with a network Tg = 53 °C, was more readily impacted by heat compared to Mixture B, whose diluent had a network Tg = 105. As a result, a higher degree of conversion, followed by an increased Tg of the diluents, and improvements in the tensile strength and dimensional stability of the printed parts were observed, which enhanced the outcomes of the prints for the intended application in investment casting of complex components used in the aero and energy sectors. In conclusion, the effectiveness of the hot lithography process is contained by a correlation between the process temperature and the characteristics of the monomers in the mixture.

Large Scale Vat-Photopolymerization of Investment Casting Master Patterns: The Total Solution

“…The measurements indicate that increasing the content of HDDA from 20% to 60% reduces the monomer conversion in photoresins. This is attributed to the covalence cross-linking of HDDA in the polymer network which results in gelation and vitrification at lower conversions after which the polymerization slows down [ 44 ]. Addition of wax has caused a reduced DC in all mixtures as wax particles can block the progress of monomer conversion process.…”

Printing Double-Network Tough Hydrogels Using Temperature-Controlled Projection Stereolithography (TOPS)

“…Additionally, this method enables the printing of highly viscous materials such as difunctional urethane dimethacrylate and triethyleneglycol dimethacrylate that exhibit a decrease in viscosity as the temperature rises. 54 ■ CONCLUSIONS TOPS allowed the printing of 3D structures while maintaining the desired temperature of the prepolymer solution. This optical technique of fabrication was demonstrated to print the DN hydrogel of acrylamide and κ-carrageenan at the resolution of 37 μm.…”

“…Further, the versatility of this single-step manufacturing process extends beyond the materials currently employed, allowing for temperature adjustment to accommodate other temperature-responsive physically cross-linking substances like agar, gelatin, and more. Additionally, this method enables the printing of highly viscous materials such as difunctional urethane dimethacrylate and triethyleneglycol dimethacrylate that exhibit a decrease in viscosity as the temperature rises …”

3D/4D Printing of Polyurethanes by Vat Photopolymerization

“…HL may cure the resin more quickly by adding heat to the process, enabling quicker print rates and higher-resolution items and mechanical properties. [23,24] Volumetric 3D printing is a variation of vat photopolymerization in which 3D items are created by exposing a volume of resin to light rather than being built layer by layer. Because the items may be formed from all directions at once, it is possible to create objects with more complex shapes and internal features.…”

“…[38] lithography vat photopolymerization 3D printing may be an effective solution to avoid the use of diluent since it improves the mechanical and dimensional properties of the printed items. [24,23]…”