and reduced cost due to limited mechanical components. The disadvantage would be limited part mobility; with no tilt or elevation capabilities, the load can only be rotated with the main work plate and part remaining parallel to the floor. Turning Rolls While turning rolls are primarily used for round vessels in the flat position, elevating and tilting (Fig. 3) models can be used for special applications as well as false rings for rotating square parts. The main limitation of using turning rolls would be the need for basically concentric parts. With friction between the wheels and the workpiece providing the rotating power, large eccentric loads may slip requiring a more rigid connection as in a head and tailstock positioner. Special engineered products and positioner options are almost always utilized in the final positioner design. Throughholes, special tables, and PLC controls are just a few solutions that can be used in the design of a special positioner application. Several features of standard positioners can be used together to make specialty positioners such as skyhooks (Fig. 4) and drop centers. These machines are a combination of several axes and components providing specific arrangements of tilt and rotation in one machine for a specific part or application. Bringing It Together Once the sequence of operation, process, accessibility issues, and safety concerns have been identified and addressed, the actual positioner design required to accomplish the job will become apparent. With an acceptable machine design established, the actual weight of the part and the fixturing, along with the center of gravity locations, will determine the capacity required of the determined positioner model.◆ 36 FEBRUARY 2014 Fig. 4 — An example of a skyhook positioner. For info, go to www.aws.org/ad-index
Welding Journal | February 2014
To see the actual publication please follow the link above