A positioner is a machine used to rotate a work piece at a constant rate and through a controlled range of positions to allow continuous processes to be carried out with ease. A good example of this is the welding positioner, which allows a welder stand in one position and weld a continuous seam around the pipe without having to move around or weld vertically. Most positioners feature a round turntable onto which the work piece is mounted. An electric motor then turns the work piece at a user-selected rate. A wide range of positioner models are available, with some smaller types being suitable for light engineering with others being capable of handling work pieces weighing many metric tons (tonnes).
Continuous manufacturing processes such as welding joints on round or cylindrical work pieces can be difficult to achieve correctly, particularly when they are carried out manually. Personnel have to work in uncomfortable positions and move about constantly, often dragging welding cables with them, neither practice being conducive to precise, consistent work. Safety also often becomes an issue when this type of working condition is encountered with stress, fatigue, and loss of concentration, leading to potentially hazardous situations. One of the more effective methods of doing away with these undesirable conditions is to use a positioner to turn the work piece rather than having the artisan move about.
The positioner is basically a work piece support structure fitted with a driven turn table. The work piece mounts on this turn table and is rotated through 360° at a rate controlled by the operator. In the case of welding positioners, this rate can be adjusted to produce optimal penetration on welding runs and does away with the need to weld vertically, always a difficult practice to execute correctly. The rate at which the positioner rotates the work piece is set on control units of varying levels of sophistication, with certain models capable of extremely precise adjustment. Although welding is by far the most common application for positioners, is not the only production process which benefits from their use, with several automated machining and fabrication applications also utilizing them.
The size and complexity of the positioner used in any specific application depends on the type of work being done. Some smaller units are suitable for light engineering or even hobby applications. Heavy duty positioners, on the other hand, are world's removed from the small units, often capable of effectively handling loads of many metric tons (tonnes).