As I said above, the two-zone web line should be the starting point for any web process. But when is 3 or 4 or 13 tension zones the right answer?
The two tension zone line is designed to compensate for the diameter changes and process needs of unwinding and winding, but in web lines, we usually do more than just rewind, we have processes with their own tensioning needs.
Adding a fourth drive point creates a third tension zone potentially independent of unwinding and rewinding. As more processes and rollers are in the web path from unwinding to winding, more tension zones and drive points may prove beneficial.