Study of the Mechanism of a Stable Deposited Height During GMAW-Based Additive Manufacturing

Gas metal arc welding (GMAW)-based additive manufacturing has the advantages of a high deposition rate, low cost, the production of a compact and dense microstructure in the cladding layer, and good mechanical properties, but the forming process is unstable. The shape of the welding bead critically affects the layer height and dimensional accuracy of the parts manufactured, and it is difficult to control. A series of experiments were designed and the results indicated that when the value of the predefined layer height is set in a certain range and other parameters are held constant, the height of the thin wall produced by GMAW-based additive manufacturing is almost equal to the predefined layer height multiplied by the number of layers. This research work shows that during the GMAW process, the changes in the distance between the torch and the top surface of the part cause a variety of dry extensions of the electrode; furthermore, the changes lead to a variety in the heat input into the molten pool. Therefore, the dry extension of the electrode is the key factor influencing the geometry of the welding bead, especially the layer height, and it has a compensating effect that makes the actual layer height close to the predefined value. A three-dimensional numerical model was established to study the influence of the predefined layer height to the fluid flow and heat transfer behaviors during the weld-deposition process.