## 3 Results and Discussion
### Deformation Analysis  
Figure 10 shows the resulting cloud map of the warping changes of each layer. The proportion of the deformation displayed is 1:1. It can be seen that the warp is concentrated at the bottom surface of the edge of the overhang structure. Previous studies proved that the warp tends to be more obvious at the edge of the overhang structure under the same conditions [4]. Figure 10 shows the deformation distribution along the \(Z-\)axis of the model. The cloud image distribution shows that the warping deformation of the top layer did not intensify all the time while the fourth layer was forming. When the model was formed to the first and second layers, as shown in Figure 10a,b, the maximum deformation area was concentrated on the overhanging area. The warping at the edge of the overhang structure is quite serious. In Figure 10c, as the processing progressed, the deformation at the top of the overhang structure began to differ from the deformation at the bottom. Figure 10 shows that the maximum deformation area did not move upward and the cloud image changed, taking the bottom of the left side of the overhang structure as the center of the circle, and gradually decreased outward. As shown in Figure 10d, the high deformation zone (red area) existed at the bottom when the fourth layer was fabricated and, with the increase in the forming layer, the deformation of the top layer was continuously alleviated compared with the third layer, as shown in Figure 10c.  
Figure 9: Schematic diagram of dross formation generation process.  
In order to understand the trend of warpage, the maximum deformation value point of each layer was selected to draw the deformation trend map, as shown in Figure 11. In the process of machining, the maximum deformation of the overhang structure increases continuously, while the increasing amplitude is not constant. As shown by the midpoint plot in Figure 11, the difference in the maximum deformation amount between the second layer and the first layer is 28.5 \(\upmu\)m. However, as the number of forming layers increased, the deformation of the top area decreased and the deformation of the parts increased continuously. The temperature gradient in the powder support zone was large, making the residual stress in the area large as well and bending occurred as the forming layer in this area had no bottom constraint and a low stiffness. In the manufacturing process of the initial two layers, the melting pool in the powder support zone of the second layer was still large. This affected the manufactured area of the first layer again in a manner equivalent to remelting the warped part of the first layer and further aggravating the overall deformation degree. When progress was made in the process, the number of formed layers increased continuously, and the stiffness of the overall structure increased as well. Therefore, when the subsequent layer was formed, the formed layer provided constraints that gradually reduced the subsequent deformation.  
Figure 11: The deformation and its increment between different layers.  
Figure 10: Deformation at different study points: (**a**) Layer 1; (**b**) Layer 2; (**c**) Layer 3; and (**d**) Layer 4.