Fabrication of sacrificial wax pattern through large-scale fused granulated fabrication (FGF-AM) hybrid manufacturing system

Direct rapid investment casting integrates additive manufacturing (AM) technology into conventional investment casting. This approach addresses the challenge of high lead time and cost but is effective only on a small scale. It utilizes thermoplastics such as ABS as a sacrificial pattern material, but after burnout, thermoplastics can lead to defects such as shell cracking and residual ash. This study uses large-scale extrusion AM technology, fused granulated fabrication (FGF-AM), to address these challenges. This approach involves printing sacrificial patterns using wax, a preferred foundry material. This novel technique can produce highly scalable objects due to its superior extrusion rate. The design of experiments is used to optimize the crucial printing parameters. In-situ CNC machining was incorporated to mitigate stair-stepping defects resulting from layer-by-layer printing and to improve surface quality and dimensional precision, ensuring compliance with investment casting (IC) standards. Tensile testing was conducted per ISO standards at different sections to assess the variations in mechanical properties along the print volume. Finally, to demonstrate the capability of the in-house hybrid manufacturing system, a case study was performed by fabricating an ASME wax slip-on flange. The developed system achieved 10–20 times higher productivity than alternative 3D printing methods, which shows its potential for industrial scalability.