# A MIG Welding Clamping Scheme for Power Battery Enclosure's Deformation Restrain
## 2 The MIG Welding Clamping Scheme of Power Battery Enclosure  
### Design of Positioning and Clamping Scheme  
The power battery enclosure is made of aluminum alloy by welding. It is mainly composed of the bottom plate, frame, lifting lugs, and other accessories, as shown in Figure 1. After fixing the bottom plate and the frame through spot welding, MIG welding is carried out to make the frame and the bottom plate become a whole.  
According to the processing requirements on power battery enclosure, the inward shrinkage of crossbeams on each side will severely affect installation of the lifting ears if the value exceed 1.2 mm. Therefore, the welding deformation of the crossbeams on both sides of the power battery enclosure need to be restrained by adjusting clamping force of the welding clamp to meet the processing requirements. The overall structural size of the power battery enclosure investigated in this paper is 1900 mm \(\times\) 850 mm \(\times\) 92 mm, and the frame height is 20 mm. As shown in Figure 2, the whole clamping scheme was divided into four modules to facilitate analysis, which is shown in Figure 2.  
In order to meet the requirements on clamping, a rotating clamping cylinder and a clamping module driven by cylinder was adopted to realize the clamping in Z and X direction respectively. In Y direction, cylinders were used to drive the hook-pull devices on clamping modules of the crossbeams to move reversely, forming a reverse hook tension to realize the clamping effect. After the enclosure was clamped, the output clamping force of the driving cylinder can be dynamically adjusted according to the welding deformation  
Figure 1: Structure of the power battery enclosure.  
Figure 2: Clamping modules.  
force, so as to counteract the welding force to effectively restrain the welding deformation without damaging the workpiece.  
### Design of Positioning and Clamping Scheme  
Bottom plate of the power battery enclosure has the characteristics of a large-area plane in the bottom and long straight planes on surrounding sides. Therefore, the surface of the bottom plate was selected as the main positioning reference plane, the inner surface of the right crossbeam was used as the guiding positioning reference plane. Moreover, outer surface of the rear crossbeam was selected as the thrust reference plane. Three positioners were used to locate the main positioning reference positioning plane according to six-point positioning principle. The welding deformation on both side crossbeams of the power battery enclosure should be restrained. The guide-localization datum surface was positioned with three positioners to improve clamping stability. The thrust reference plane was positioned by one positioner.  
Comprehensively considering the positioning reference and the direction of external force, action direction of clamping force of the power battery enclosure was determined as follows. The clamping force in the X-direction acts on the positioning reference pointing to the X-direction (i.e., rear crossbeam of the power battery enclosure), the clamping mode of the hook-pull was adopted in the Y-direction, and the clamping force was directed to left crossbeam of the power battery enclosure, so as to realize clamping in the Y direction and restrain welding deformation, clamping force in the Z-direction points to the main positioning datum, namely the bottom plate of the power battery enclosure. The clamping force is consistent with the gravity direction, which can ensure that the required clamping force can be reduced on the premise of reliable clamping.