There are two types of drives for seam weld wheels. One is driven by the central hub, direct drive. The other is driven by knurled wheels riding on the perimeter of the seam welding wheels, indirect drive. There are pros and cons for both systems.
The knurl drive system provides a constant linear wheel speed at all wheel diameters. It can also be used to dress one or both wheels. One negative is it leaves a knurl patter on the part face.
The driven hub can operate with just one wheel driven. It is a very positive drive. However as the wheel diameter decreases the part linear speed decreases. This has to be compensated for to maintain proper weld spacing. With driven hubs wheel dressing may need to be done off line at a lathe by trading out with another set of wheels.
Seam Welder with Knurled Drive Wheels
Hub Driven Barrel Seam Welder
Part specifications size and geometry will probably dictate which drive system is best for the application.
Reference: RWMA – Resistance Welding Manual Section 4