Welding-positioner:best position and highest weld rate.SOLUTIONS with Effective, Powerful AdviceWelding-positioner: is it a special accessory tool or manipulator that helps achieving the required economic results of a welding program? It all depends on the process used, on what is going to be welded, on quantity and quality of what has to be provided, and on whether the Return on Investment (ROI) is going to justify the expense for procuring the tool. But one should also ask: Welding-positioner is an advanced implement that helps perform welding. It keeps in place the elements being welded, while providing some relative, progressive, smooth movement between the torch of a fusion welding head and the joint to be welded. The movement is relative, because it does not matter if the arc source or the work is fixed, while the other element moves along simple lines. A welding table, although very useful, has no intrinsic movements available so that it falls short of the above definition. Welding-positioner is a necessary tool for highly productive mechanically assisted manual welding for those different processes that supply filler metal continuously from a spool (GMAW, FCAW, SAW) or for GTAW with thin sections if filler metal is not required. It should be noted that only clamping the work is generally not good enough. A set of uniformly placed good quality tack welds has to be made to bridge the gap and to provide some rigidity against the stresses, developed during welding, that tend to displace the edges of the joint. A Welding-positioner assures enhanced quality and increased productivity. This is the most important gain, because of reduction of downtime, and also as the welding parameters can be selected to provide the maximum weld deposition rate, compatible with acceptable (not excessive) heat input. Arc-on time is equally increased resulting in potential reduction of welding costs. The arc torch is fixed to some adjustable clamp, not hand held. It is different from a robot in that operator's continuous surveillance and intervention are essential for successful work. Welding-positioner helps save one's strength, it is welder friendly. Welding parameters can be optimized for maximum weld metal deposition rate, over and above the values acceptable for manual welder's personal comfort. Furthermore new parts of the joint are presented continuously in the most advantageous flat position so that high quality welding can be performed with high productivity. Besides loading and unloading the positioner, the operator's task is starting and stopping the operation, keeping the weld centered along the joint, and performing minor parameter corrections as may be necessary from time to time. A Welding-positioner can be designed for linear or for circular welding. For circular welding in a vertical plane, the torch is placed in an appropriate location. It is common practice to station the torch or welding head not at the top (the 12 o'clock position) but somewhat displaced, between 10 to 11 o'clock, to ensure a slightly longer solidification time and to obtain more consistent results. It should be noted that different outcome can be obtained simply by changing the rotation direction (clockwise or counterclockwise looking from the tailstock, for the above torch position). Clockwise rotation is then equivalent to vertical down, counterclockwise is equivalent to vertical up. Tests should be done to find the best parameters. Heavy horizontal cylinders to be welded at their ends are rolled gently on multiple pairs of turning rolls, called also welding rotators, but lighter pipes can be welded while held in the chuck of a Welding-positioner resembling a lathe. The versatility of a normal lathe is limited because of gear ratios present, so that continuously variable speed is not available. Longer pipes are clamped between a Welding-positioner headstock and its tailstock. For circular welds in a horizontal plane the Welding-positioner is a turntable (vertical axis), with variable rotating speed. The rotation of the assembly, with adjustable speed, should be uniform, without stops or jerks. If the plane of welding is inclined for getting the weld in flat position, the turntable must be able to be tilted without toppling. Special positioner of different design are offered to cover the most diverse requirements. Most important characteristics are stability, especially with heavy loads, and smooth movement even at low speeds. As a young engineer, I was called, more than forty five (!) years ago, to build in house, at the small company I was working for, a simple contraption to present to the operator for manual torch braze-welding, the fillet joints of end fittings mounted on irrigation pipes. Up to that time, the job of rotating the pipes had been performed manually by a helper, while the welder was busy with his job. The pipe was inclined, so as to keep flat the braze-weld face, and was slowly rotated: the conventional designation for such a position is 1F. The device I designed had the pipe rotating on rubber rolls driven by an electric motor through a gear reduction unit. A pedal operated clutch permitted the operator to disengage the drive, should it run too fast. Simple as it was, this gadget reached its purpose, disposing of the need for a helper. Essentially it could well have been called a Welding-positioner. A linear Welding-positioner has usually a Side Beam Carriage capable of moving along a precisely ground beam on which the carriage rides, smoothly self propelled by a variable speed electric motor. The torch and the filler metal spool with its feeding unit and feed speed control are mounted on the carriage to perform the straight line welding. The beam track can be laid down and fastened near the joint to be performed. The track could also be mounted on an orientable boom or be a part of a seam welding fixture. Such a Welding-positioner is designed to permit clamping the edges of sheets to be butt welded together along a straight line, by the use of adjustable fingers or short bars pressing against a support. Often the sheet sides to be welded are both edges of a sheet rolled to form a cylinder. The design limits of the fixture are the minimum and the maximum diameter of the cylinder that can be accommodated, and the maximum length of the weldable part. The boom or shaft carrying the backing bar under the joint is hinged at one end, and clamped at the other end to the fixed parts of the fixture. The clamp must be opened and the boom released to free and extract the completed cylinder out of the fixture. A good Welding-positioner can also reduce the risks of accidents during handling of parts to be welded. As long as a constant backlog of work can be ensured to the positioner it is quite safe to assume that it is paying for itself with better quality and increased productivity, while reducing the amount of work in progress. The justification for the capital outlay needed for purchasing and operating a Welding-positioner is easily found if the increased productivity permits a more economic manufacture of repetitive work. A Welding-positioner built by a serious company with a good record of satisfactory customer service should be selected. It is recommended to consider performance exceeding that of the actual job at hand, to prepare for future expansion. An informative review of fixtures and Welding-positioners, with detailed descriptions and pictures, can be found in Chapter 9 of the AWS Welding Handbook An Article on Welding Rotators was published (2) in Issue 65 of Practical Welding Letters for January 2009. Click on PWL#065 to see it. Any specific questions? 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