Plastic Screw Conveyor Design Like most screw conveyors, plastic screw conveyors are generally powered by an electric motor. They are available in six, nine, or 12 inch diameters and may be any length, which is defined by the amount of space the facilities have. While plastic conveyors are used when impact and abrasive wear is a problem, they do have some limitations. Static electricity may accumulate and produce a spark while plastic screw conveyors are in motion. Therefore, absolutely no combustible or flammable materials may be transported via plastic screw conveyors in order to ensure workplace safety. All plastic components of screw conveyors - the screw shaft and trough or tubular casing - are manufactured by the injection molding process, where molten thermoplastic resin is forced into a mold, where it takes shape and hardens. Injection molding is fast, inexpensive, and able to produce complex plastic parts. Screw conveyors made of plastic maybe three different orientations: horizontal, which transports material on a level plane and often doesn't require a tubular casing; vertical, which conveys material straight up and down; and inclined, which moves material from one container to another on an angle. Most plastic screw conveyors, however, are modular or portable. They are smaller and can be relocated to anywhere they are needed around a facility.