Welding defects should of course not occur. Nevertheless, it must be made clear beforehand what a mistake is. Defects are understood to be irregularities in the weld joint, as well as deviations from the intended shape and position of the weld joint and the weld lens or weld seam. Depending on the application, different quality characteristics are defined and used for the welded joints.
These range from the point or lens diameter or its minimum dimension or tolerance values, the lens thickness, the minimum shear pull force, the minimum head pull force to the surface quality, the penetration depth or the freedom from spatter. The most common parameters are usually the point diameter and the minimum shear tensile force. If the specified or agreed values are not achieved, this is referred to as a welding defect.
At this point, it should also be pointed out once again that the point diameter is larger than the actual lens diameter. In practice, the point diameter is usually determined because of the lower testing effort (DVS 2902 Part 3). In order to avoid welding errors as much as possible, adaptive control systems such as the IQR system are used for the most part. But that is a separate topic again.