The spot welding of the spot welding machine usually adopts the lap joint and the lap joint. The joint can consist of two or more workpieces of equal or unequal thickness. In the design of spot welding structure, the accessibility of the electrode must be considered, that is, the electrode must be able to easily reach the welding part of the workpiece. At the same time, factors such as edge distance, overlap amount, solder joint distance, assembly clearance and solder joint strength should also be considered.

 

The minimum edge distance depends on the type of metal to be welded, thickness and welding conditions. Smaller values ​​may be used for metals with high yield strength, flakes or high strength metals.

 

The smaller value of the specified point distance is mainly to consider the effect of shunt. When the use conditions are strong and the electrode pressure is large, the dot spacing can be appropriately reduced. When using thermal expansion monitoring or controllers that can sequentially change the current at each point, and other devices that can effectively compensate for parallel effects, the point spacing can be infinite.

 

In the spot welding process, the gap between the two workpieces must be as small as possible, because eliminating the gap through pressure will consume part of the electrode pressure and reduce the actual welding pressure. The unevenness of the gap can cause fluctuations in the welding pressure, which can cause significant differences in the strength of each weld. Excessive clearance can also cause severe splashing. The allowable clearance value depends on the stiffness and thickness of the workpiece. The greater the stiffness and thickness, the smaller the allowable gap, generally 0.1-2mm.

 

The strength of a spot welded joint is positive tensile strength under a tensile load perpendicular to the direction of the panel. Since the sharp corners between the two metal plates around the solder joint will cause stress concentration and reduce the actual strength of the solder joint, the solder joint is generally not loaded in this way. Usually, the ratio of positive tensile strength to shear strength is used as an index for judging joint ductility. The larger the ratio, the better the ductility of the node.

 

The strength of a joint formed by multiple solder joints also depends on the spacing and distribution of the solder joints. When the pitch is small, the strength of the solder joints is affected by the shunting, while larger pitches limit the number of solder joints that can be placed. Therefore, greater joint strength can only be obtained by considering the distance of the solder joints and the number of solder joints. Multiple columns of solder joints should be staggered, not rectangular.