system also varies. The cost of downtime from feeding problems and replacement parts can be significant as well. For these reasons, you should choose the feeding system that is best suited to your application and set it up to optimize its feeding capability. Push and Pull Only Feeders. These systems are generally limited to a practical length of about 12 ft. With the push feeders, the feeding distance limit is a result of the flexibility of the aluminum wire and its tendency to buckle and bend in the liner. With the pull feeders, it is a result of a rapid increase in friction drag in the liner, particularly if there are bends in the conduit. Push-Pull Feeders. This feeding system was developed to overcome the wire feeding problems experienced by the other systems, and these systems are the most positive method of feeding aluminum welding wire. The pushpull systems can improve feedability in many applications and are often essential for more critical/specialized operations such as robotic and automated applications to ensure consistent feedability. While typically more expensive than other feeding systems, the pushpull system is a definite asset in assisting with the feedability of aluminum weld wire. Spool-on-Gun Feeding System. This system is usually designed to use 1-lb spools of wire that are mounted in the gun. These guns are usually air cooled and generally limited to smaller wire sizes and light-duty service. Because of their relatively low current rating, they are not perfectly suited to heavy-duty continuous production welding, but are often quite effective for tack welding and other light-duty applications. Welding Equipment. Taking a GMAW system designed and used for steel and attempting to convert it for use with aluminum may not always be the simplest or most effective method of creating a reliable aluminum GMAW system. Most welding equipment manufacturers today make GMAW systems dedicated to welding aluminum. These systems have feeding equipment specifically designed and configured for aluminum weld wire, and they also have power supplies that are preprogrammed for the various types of aluminum weld wire. Conclusion When changing from welding steel to welding aluminum with GMAW, for optimum aluminum weld wire feedability, consideration must be given to the following items: Steel Wires — rigid, feed more easily over a greater distance, and withstand far more mechanical abuse. Aluminum Wire — softer, more susceptible to abrasion, requires more attention when purchasing and setting up the feeding system. Spool Brake Setting — tension set at a minimum, only sufficient brake pressure to prevent spool from freewheeling when stopping. Liners, Inlet and Outlet Guides — made from nonmetallic material such as TeflonTM, nylon, or plastic to prevent abrasion or shaving. Drive Rolls — designed specifically for aluminum, U-type contours with chamfered edges, rolls aligned and adjusted to provide correct drive roll pressure. Contact Tips — need to be made specifically for aluminum, smooth internal bores, polished, absent of sharp burrs, and bore diameter 10 to 15% larger than wire. Weld Wire Quality — cleanliness, wire surface smoothness, and wire diameter control. Type of Feeding System — most appropriate for application, push, pull, push-pull, or spool-on-gun feeding systems. 24 WELDING JOURNAL / JUNE 2016 WJ TONY ANDERSON is director of aluminum technology, ITW Welding North America. He is a Fellow of the British Welding Institute (TWI), a Registered Chartered Engineer with the British Engineering Council, and holds numerous positions on AWS technical committees. He is chairman of the Aluminum Association Technical Advisory Committee for Welding and author of the book Welding Aluminum Questions and Answers currently available from the AWS. Questions may be sent to Mr. Anderson c/o Welding Journal, 8669 NW 36th St., #130, Miami, FL 331666672; tony.anderson@millerwelds.com. For info, go to aws.org/adindex Change of Address? Moving? Make sure delivery of your Welding Journal is not interrupted. Contact Maria Trujillo in the Membership Department with your new address information — (800) 443-9353, ext. 204; mtrujillo@aws.org.
Welding Journal | June 2016
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