a load of plastic material is formed from two sheets cut successively from a roll of strip material . the first sheet is cut to a roughly constant length , weighed and loaded on to a conveyor . the second sheet is cut to the length calculated according to the weight of the first sheet and is loaded on to the conveyor in a predetermined position in relation to the first sheet . each sheet is positioned by transferring it from the cutting station to a transfer structure moved in relation to a stop structure set each time to a given programmed position .