Welding lap joint and usually fold joint connector can be two or more ranges such as the thickness of the workpiece thickness or composition. Spot in the design of the structure, we must consider the accessibility of the electrode, the electrode must be able to easily reach the welding position of the workpiece. Should also be considered, such as margins, overlap volume, pitch, assembly gaps and joint strength of various factors.

The minimum margins depending on the type of welding wire , thickness, and welding conditions. For high yield strength of metal, thin pieces, or less desirable conditions with strong values.

Pitch is the center distance between two adjacent, the minimum and welded metal thickness, conductivity, surface cleanliness, and the nugget diameter.

Pitch minimum requirement is mainly on account of diversion, the use of high pressure conditions, and large electrode, the pitch may be appropriately reduced. Thermal expansion can be used to monitor or change the order of the controller of the point current, and effective compensation for diversion of the other device, dot pitch can be unlimited.

Assembly gap must be as small as possible because space will be consumed by the pressure to eliminate part of the electrode pressure, the actual welding pressure is reduced. Inhomogeneity of the gap and make the mig welding wires fluctuations, which led to the significant difference in joint strength, the gap is too large would cause serious flying, the allowable gap value depends on the workpiece stiffness and thickness, stiffness, thickness greater allowable gap smaller, usually 0.1-2mm.

Single solder joint shear strength depends on the junction of two plates nugget area, in order to ensure the joint strength, nugget diameter, in addition, the penetration rate and the indentation depth should also meet the requirements for the penetration rate of expression: η = h / δ-c × 100%. Two panel penetration rate is only allowed between the range of 20-80%. Magnesium alloy penetration rate is only the maximum allowed to 60%. The alloy is allowed to 90%. Welding of different thickness of the workpiece, each workpiece penetration rate of the minimum for thin joints in 20% of the thickness, the indentation depth should not exceed 15% of the thickness of plates, if the two workpiece thickness ratio greater than 2:1, difficult to close the site or in the welding, and using flat side of the workpiece electrode, the indentation depth can be increased to 20-25%. Figure 11-10 shows the low times of grinding on the nugget size.

The vertical direction of the panel by spot welding joints, the tensile load, strength, tensile strength is positive. As the nugget around sharp corners formed between the two plates can cause stress concentration, leaving the actual nugget strength decreased, which generally do not load the spot weld. Usually are tensile strength and shear strength of joints to determine the ductility ratio as an indicator, this ratio is larger, the better the ductility of joints.

Multiple solder joint strength will also depend on the formation of pitch and solder joint distribution. Pitch-hour joints be affected because of segregation strength, large dot pitch will limit the number of solder joints can be arranged. Therefore, we must take into account the pitch and the number of solder joints in order to obtain maximum joint strength, multi-column joints staggered and not the best arrangement for the rectangle.