# DLP Light-Curing 3D Printing Combustible Lighting Shell and Performance Study
###### Abstract  
In order to further improve the luminous intensity of illuminating flares, the technique of 3D printing of the combustible shell of the illuminating flare using DLP light-curing was proposed, and the combustion spectrum of the combustible shell was made consistent with the combustion spectrum of the illuminating agent. A combustible illuminating candle shell slurry formulation was designed, with light-curing resin, magnesium powder, and sodium nitrate as the main components, and was printed and molded by DLP light-curing 3D printing technology to test its luminescence properties, mechanical properties, compatibility, and moisture absorption. The results show that the optimal formulation mass fraction of energy-containing slurry for the 3D printing of the combustible lighting candle shell is 50% for light-curing resin, 41% for sodium nitrate (NaNO\({}_{3}\)), and 9% for magnesium powder (Mg). The mechanical properties of the shell are good, with tensile strength up to 9.82 MPa and compressive strength of 102.86 MPa, and the compatibility of the components of the formulation is good, with stable combustion, and can provide 4.73% of light intensity for the lighting candle. combustible shells; light-curing 3D printing; luminescence properties; mechanical properties 13 September 20221  
Commonly used illuminating candle shells have two types of structures: integral and non-integral. The integral illuminating candle shell is formed by stamping and cold drawing, and is connected by edging. It has the advantage of high strength. The non-integral illuminating candle shell is welded by two parts: a cylinder and a circular plate. Both integral and non-integral structures need to use a mold with fixed size, and the processing and forming method is more complex than the 3D printing and forming method. In particular, 3D printing is stacked layer-by-layer by extrusion [7], melt deposition [8], light-curing treatment [9], jetting [10], etc., which can enable the shell's rapid prototyping at one time. The printing structure is freer and the process is controllable. Since traditional technology requires the establishment of production lines, 3D printing is different from the traditional process. It not only does not require molds, but greatly simplifies the production and manufacturing process, which can effectively reduce the production costs such as human and material resources. In addition, when the traditional process is used to manufacture parts, it requires multiple pieces of equipment or even multiple production lines to cooperate. Therefore, compared with the traditional process, 3D printing also improves production efficiency. This technology is widely used in aerospace, casting, biopharmaceutical, and food processing fields [11]. In the field of manufacturing energetic materials, 3D printing technology is commonly used for the manufacturing and molding of propellant powder [12; 13; 14] and propellants [15]. [PERSON] et al. [16] designed a CL-20-based ink with uniform dispersion and proper rheology, which will not cause caking or nozzle blockage, and the printed finished product has a high burning speed. Therefore, it is feasible to print an energetic slurry by direct writing 3D, but extrusion will increase the local pressure of grains, which is very dangerous to some extent. Compared with extrusion, melting, and other methods, UV curing 3D printing technology can better ensure the safety of printing energetic materials. It also has the characteristics of high production efficiency, less pollution, energy savings, and excellent performance of cured products [17; 18]. In order to improve the complex forming process of a uniquely shaped charge, [PERSON] [19] printed a uniquely shaped energetic charge with light-curing technology, which provides stable combustion and a fast burning speed. [PERSON] et al. [12] prepared a propellant composed of APNIMMO and CL-20. Through UV light-curing 3D printing, it was found that an energetic resin system can greatly improve the combustion rate.