At forming an image only on one side of a sheet, an image forming unit is controlled by a control unit to form a back-side pattern image on the back side of the sheet. The system is particularly well suited for unwinding soft, high-bulk tissue webs. Based on the determined voltage drop, a drain bias voltage actually applied to the drain of an FET is determined. The process may also be performed in an inert gas environment. Offset hinged plates connect modules, forming large structures.