There are three main types of FRP production process: reciprocating filament winding process, continuous filament winding process and centrifugal casting process.
Reciprocating filament winding process (belongs to length method): In this process, the dipping trough moves reciprocating with the rotating mandrel, the long fiberglass filament is placed with a certain oblique angle relative to the mandrel axis, the auxiliary angle (i.e. the winding angle) is controlled by the ratio of the moving speed of the dipping trough to the rotating speed of the mandrel, and the translation motion of the dipping trough is controlled by computerized machine-electricity. The number of winding layers increases gradually until the designed wall thickness is reached. After winding, the resin in the product is basically cured. After curing, the core die is removed from the FRP pipe.
Continuous filament winding process (belongs to continuous method): This process is a pipe in motion through a feeding station for resin prepreprepreg roving, chopped fiberglass reinforced plastic fiber and resin sand mixture, the pipe is made in the continuous progress of the core mould.
Centrifugal casting process (belonging to length method): In this process, cut glass fiber reinforced materials and sand are fed into the steel mould on the bearing, and unsaturated resin with catalyst is injected into one end of the steel mould to impregnate the reinforcing material. Under the action of centrifugal force, the resin replaces the air in the fibers and fillers, thus producing porous and compact composite materials. A smooth and smooth resin-rich inner surface layer is formed on the inner wall of the tube under centrifugal force, and the tube solidifies at a higher temperature. The pipe manufactured by this method is also called FRP sandwich pipe.
There are more manufacturers using reciprocating filament winding process than the other two processes in the world. One of the reasons is that the FRP pipe manufactured by reciprocating filament winding process has a wider use and better applicability.