The invention relates to a system for preforming an extruded plastics parison including a nonplanar conveyor belt. It also relates to a method for preforming an extruded parison, including a step during which the parison is deposited on a conveyor belt. The conveyor belt is not planar. This step may be accompanied by a step in which the parison undergoes transverse deformation. The invention also relates to a method of manufacturing at least one article, including such a preforming step.