Abstract: A machine for manufacture of products formed by welding of plastic film sheets is disclosed comprising a welding station, a cutting station, and a conveying apparatus which serves to guide the plastic sheets through the stations. The conveying apparatus consists of a moving carriage with grasping devices for grasping the plastic sheets. The carriage comprises a cam slot extending perpendicular to its direction of motion. A driven cam follower engaged in the cam slot drives the carriage from a first position, in which the grasping devices grasp the sheets, into a second position at the end of the feed carriage travel, at which the sheets are released. A conveyor belt supports the film sheets between the various stations. A lift mechanism activates the welding press during the reverse motion of the carriage; it is driven by the drive shaft driving the crank arm. The speed of the motor driving the drive shaft may be varied during each machine cycle to optimize its operation.