This production line is used to produce sandwich panels for making automatic doors with the middle layer of rigid polyurethane foam and with aluminum sheet or colorsteel sheet as the top and bottom face layers. The laminated panel is between 30 and 100 mm in thickness, 350~700mm in width, length determined by the customer. The operation principle of this line is as follows: PU raw materials are delivered into the mixing head through the metering pump and then evenly injected onto the bottom facing sheet going toward conveyors along with the top superficial sheet. Between the upper and lower conveyors, the liquid materials start foaming and are hardened into shape, after which the formed door panel is, by an automatic tracking cutter, cut into segments according to preset length.
　　The production line for door panels is the same as the line for wall and roof panels in terms of structure and operation principle.