a system for supporting , guiding and controlling a welding head to maintain the welding head normal to the instantaneous surface contour of overlapping , convoluted metal sheets to weld the same together . the system is capable of being supported on the convoluted metal sheets regardless of the relative orientation of the sheets . in order to maintain a preselected penetration , consistently throughout the welding of the sheets , the orientation of the weld head , the amount of heat developed at the weld head and the rate of speed of travel of the weld head are precisely regulated . the orientation of the weld head relative to the sheet is controlled by a mechanical sensor which activates a preprogrammed configuration device displaying characteristics substantially identical with any particular departure from the normally linear surface of the sheets . with the exception of the departures from the linear portion of the sheets , the system is programmed to proceed linearly according to predetermined conditions .