Shimizu Corporation has developed technology that uses material injection 3D printing to automatically print structural parts reinforced with integrated rebars. The robotic arm, which can move like a human arm, is controlled and carries out each process in sequence, including pumping material into pre-assembled rebars, surface finishing and measuring finished product. In a demonstration test, we successfully printed a column element (cross-sectional dimensions: 510 mm x 210 mm, height: 1.5 meters) with an error of plus or minus 5 mm or less.
Finished shape of reinforced structural elements (from press release documents)
In 2019, the company developed Rakutum, a fiber-reinforced cementitious composite material for extrusion-type 3D printing, with the aim of commercializing 3D printing for construction and has used it in projects construction and civil engineering projects. Because the media extrusion die extrudes the media directly below the nozzle and stacks the layers, the vertical rebars cannot be integrated into the model, making it difficult to directly model the parts Reinforced structure.
The company focuses on material injection 3D printing technology, which creates objects by spraying printing materials from a nozzle using compressed air. We have developed the technology to print reinforced structural parts by spraying a newly developed printing material for injection molding from the outer periphery of the rebar.
Using a robotic arm 3D printer, the printed material is sprayed diagonally downward from a nozzle at the tip of the robotic arm that rotates around the outer perimeter of the reinforcing steel. After filling the inside of the reinforcement, different combinations of surface printing materials are sprayed onto the entire surface layer. The robotic arm handles everything from leveling surfaces with a trowel to measuring finished products with 3D scanning.
Objects made using this technology also have excellent structural performance. Load test results on beam components show that the structural strength and durability are equal to or higher than RC components constructed by conventional construction methods. In the future, we will aim to improve materials and improve robot sensor technology, improve mold precision, and establish printing technology for complex shapes. Technological development will be promoted with a view to its application in repair and strengthening of existing structures and emergency rehabilitation.
