The number and spacing of spot welds will depend upon many factors. The material being welded for example – steel or aluminum. What type of part is being welded – a hair dryer or an automobile? Is the weld a structural weld? Is it a considered a safety weld? Shunting current must be avoided between welds that are too close together.
Reference Article: IS THERE A MINIMUM SPACING BETWEEN SPOT WELDS?
These and many other factors are considered by design engineers when they specify the number and location of spot welds. A full discussion of this topic is beyond the scope of this blog.
Reference: RWMA Resistance Welding Manual 4th Edition