Thermal sensing and heat input control for thin-walled structure building based on numerical simulation for wire and arc additive manufacturing

In the wire and arc additive manufacturing process, the cumulative temperature increase caused by the repeated deposition process reduces the dimensional accuracy of the build structure. When the temperature of the build structure increases, the deposited metal width increases, while the height decreases. In this case, using a lower heat-input condition is effective because the temperature near the molten pool can be locally lower and the molten pool size can decrease. Thus, the height of the build structure can increase, and the uniformity of the deposited metal width can be improved. In this paper, a heat-input condition control system is proposed. This system controls the voltage-a heat input condition-which is applied from the welding power source according to the temperature of the build structure. The temperature of this structure is measured using a radiation thermometer during the deposition process. To determine the optimal voltage value, the relationship between the build structure temperature and the deposited metal shape is estimated by a numerical simulation. The optimal heat input condition is derived based on simulation results with varying preheat temperatures and heat input conditions. By using numerical simulations, the number of experiments can be minimized. To evaluate the proposed method, a thin-walled structure was built, and its profile was measured. The accuracy of the build was successfully improved by using the proposed method.