Development of a cooperative system for wire and arc additive manufacturing and machining

Wire and arc additive manufacturing (WAAM), which is an additive manufacturing (AM) process that uses metal materials, has a higher fabricated volume per unit time but a lower fabricated shape accuracy compared with other methods. With this process, the surface roughness of fabricated objects is several hundred micrometers or more, and a finishing process is necessary. However, the fabricated objects after finishing can have uncut areas or can be overcut during the finishing process owing to the large difference between the target and actual fabricated shapes. Therefore, the objective of this study is to develop a cooperative system for WAAM and machining that includes a process that measures the shape of the fabricated object. First, the three-dimensional (3-D) shape of the fabricated object was measured by structure from motion (SfM) and compared with the 3-D computer-aided design (CAD) data. Second, the original design was modified, and the amount of material removed during finish cutting was optimized with the developed software. Finally, the fabricated hollow object was finished by milling to obtain a uniform wall thickness without any defects. A 3-D fabricated object was measured by SfM, and it was observed that the measurement accuracy was sufficiently high for the requirements of the system. In addition, a fabricated hollow quadrangular pyramid with a closed shape was machined with a computer numerical control (CNC) machine tool with the modification of the work origin. As a result, the amount of material removed during finish cutting was optimized, and the inclined wall thickness was uniform compared with that without modification. In addition, a hollow turbine blade with a freeform shape was successfully finished without any defects.