Idle time selection for wire-arc additive manufacturing: A finite element-based technique

Wire-arc additive manufacturing is a metal additive manufacturing process that enables the production of large components at a high deposition rate. This process transfers a large amount of heat to the workpiece, requiring the introduction of idle times between the deposition of subsequent layers so that the workpiece cools down. This procedure prevents the workpiece from collapsing and ensures a suitable interpass temperature. The main challenge is the selection of such an idle time capable of ensuring the required interpass temperature, because the cooling rate of the workpiece changes throughout the process, entailing the need for a different idle time between the deposition of subsequent layers to achieve a constant interpass temperature. This paper proposes an innovative approach to schedule the deposition of interlayer idle times for wire-arc additive manufacturing process. The technique is based on a finite element analysis of the thermal behavior of the workpiece, by solving the heat transfer equations. The simulation data are processed using the developed algorithm to compute specific idle times for the deposition of each layer, thereby ensuring a constant interpass temperature. The effectiveness of the proposed technique is validated by experiments performed on a test case component. The idle times are calculated using the proposed technique, by simulating the process, and used to manufacture the test case. The temperature data measured during the process are compared with the FE simulation results to verify the accuracy of the model. An analysis of the geometry of the manufactured workpiece confirms that the adoption of the idle times obtained by the proposed technique prevents the occurrence of major structural collapses.