Fabrication and performance evaluation of HMX-based combustible cartridge cases via top-down DLP 3D printing

This study focuses on 3D-printed combustible cartridge cases (CCCs) to address the limitations of traditional mold-based manufacturing in producing high-performance CCCs with complex structures, and verify the feasibility of 3D printing for this application. The CCCs were fabricated via top-down digital light processing (DLP) using a slurry composed of HMX (solid filler), high-strength photosensitive resin (binder), and TPO (photoinitiator, 3% of binder mass). The HMX-based combustible cartridge case has a higher force constant, decomposition temperature and is less sensitive to mechanical stimuli, and features a longer cook-off time. Key printing parameters were optimized based on critical exposure energy ( E c = 12.68 mJ/cm 2 ) and slurry penetration depth ( D p = 0.83 mm): an exposure time of 2 s (ensuring sufficient curing and stable mechanical properties) and a layer thickness of 0.15 mm (≈ 0.18 × D p , balancing efficiency and strength). Performance tests showed the 3D-printed CCCs had an energy power of 692 J/g, excellent thermal stability (onset decomposition temperature: 242.01 °C via DSC-TG), and favorable mechanical properties under optimized parameters: tensile strength of 19.54 MPa (comparable to traditional mold-pressed CCCs) and compressive strength of 44.82 MPa (significantly higher than traditional ones), ensuring structural integrity. Trials with a 12.7 mm test gun revealed that loading 12 g single-base propellant into a 3 g 3D-printed CCC achieved a chamber pressure of 224 MPa and projectile velocity of 697 m/s (values comparable to those with 16 g single-base propellant), proving no interference with main propellant energy release. This study validates 3D printing for CCC production and provides insights for parameter selection in vat photopolymerization-based energetic material printing. • Top-down DLP 3D printing helps to fabricate complex CCCs. • 3D-printed CCCs show good mechanical performance and accuracy. • HMX-based CCCs demonstrates better heat resistance. • Printed CCCs show good interior ballistic compatibility.