Different Sized Metal Reinforcement Insertion System Using Cartridge Replacement Mechanism for 3D Concrete Printer

3D Concrete Printing (3DCP) systems with the additive manufac-turing (AM) method are attracting attention as a technology enabling highly free-shaped concrete structures. On the other hand, the discontinuous surfaces between the layers are structural weakness. To overcome this, we propose a printing method in which reinforcements are inserted to penetrate between layers during printing. The 3DCP using this proposed reinforcement method is ex-pected to create free-form structures with reinforcement that include curved sur-faces and overhangs without limiting the number of layers. However, a mecha-nism that inserts reinforcements of different sizes is needed to make freeform shapes. In this study, we propose a novel insertion system that enables the dif-ferent-sized reinforcements insertion by replacing the pre-loaded cartridges. The proposed insertion system is a compact size (250× 160 × 630 mm) and light weight (1.7 kg). Thus, it can be retrofitted to existing 3DCPs. It is mounted to the 3DCP nozzle and is controlled using the positioning mechanism of the 3DCP itself. By replacing the pre-loaded cartridge with the different-sized reinforce-ments, the device enables the automatic insertion of metal reinforcements of dif-ferent lengths (30 – 60 mm) in conjunction with the 3DCP. Inserting the rein-forcement through the linear bush reduced the surrounding voids of the inserted reinforcements by 99% compared to manual reinforcement insertion. Using the proposed reinforced system, we successfully demonstrated the applicability of the reinforced desk and chair-shaped structure, featuring curved surfaces and dimensions of 600 mm in height and 900 mm in length with the insertion of tai-lored length reinforcements based on the structure's geometry. This experiment highlighted the adaptability of reinforcement for complex and highly free-shaped geometries in concrete 3D printing.