When spot welding with different thickness or different materials is carried out, the welding spot will be asymmetric to its interface, but offset to the side with poor thickness or conductivity and thermal conductivity. As a result, the penetration rate of thin parts or workpieces with good conductivity and thermal conductivity will be reduced and the strength of the welding spot will be reduced. The solder joint offset is caused by the different melting point and quality of the two workpieces. When the thickness is different, the resistance on one side of the thickness is large, and the interface is far away from the welding head, so the heat generation is more and the heat dissipation is less, resulting in the deviation of the welding joint to the thick part; When the materials are different, the materials with poor conductivity and thermal conductivity are easy to produce heat and difficult to dissipate heat, so the solder joints are also biased towards this material.

Principle of adjusting nugget offset:
Increase the heat production of thin plate or workpiece with good conductivity and thermal conductivity and reduce its heat dissipation. Common methods include: adjusting nugget offset common methods:
1. Adopt strong conditions: increase the influence of contact resistance between workpieces on heat generation and reduce the influence of electrode heat dissipation. The capacitor energy storage ultrasonic welding machine for ABS plastic can weld workpieces with large thickness ratio by using high current and short power on time.

2. Use electrodes with different contact surface diameters: use smaller diameters on one side of thin parts or workpieces with good conductivity and thermal conductivity to increase the current density on this side and reduce the influence of electrode heat dissipation.can weld workpieces with large thickness ratio by using high current and short power on time.