One of the most recent developments is the shaftless screw conveyor which utilizes a screw without the center pipe. The screw or spiral is constructed from high-strength steel and is rigid enough to handle the drive torque. The spiral typically lies in the bottom of the trough on a liner made from UHMW plastic or metal. The drive shaft is connected directly to the shaftless spiral. The shaftless conveyor was originally developed to convey wet and sticky materials. When conveyed with a shafted screw conveyor, wet and sticky materials have a tendency to stick to the pipe where the flight is attached. Since the center pipe is eliminated in a shaftless conveyor, there is no place for the material to stick. The image below shows a typical shaftless screw conveyor