a paperboard tray forming machine is disclosed which is designed for forming a paperboard tray from a flat production blank . the paperboard tray has front and rear end panels hingedly attached to side panels by means of folded gusset corner panels . the tray further has folded over corner flaps hingedly attached to the gusset panels and upwardly turned top flaps hingedly attached to the front and rear end panels . the machine is formed in a plurality of stations designed to take a paperboard flat production blank from a hopper and to fold the tray into the finished shape through a series of folding and glueing stations in the machine . the path of travel through the machine is in a generally u - shape . the various folding and glueing stations are positioned around an endless traveling conveyor having a plurality of mandrels attached thereto . the carton blank advances first in one direction and then turns in a u - shaped path and advances in the opposite direction . the folded carton is then stripped from the mandrel to be passed to a filling station forming no part of the invention .