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Equipment For GMAW Welding of Aluminum
The selection of equipment for welding aluminum requires an understanding of the differences in power supplies and the various features available within that equipment. Consideration should be given to those equipment characteristics, which are most favorable for the specific welding application to be performed.
Power Supplies: Power supplies used for welding aluminum are typically either Constant Voltage (CV) or Constant Current (CC). Constant Voltage equipment is designed to provide a consistent arc length and a more consistent weld profile. With the CV mode, the penetration will vary as a function of the changes in amperage needed to maintain the constant voltage (arc length).
Constant Current equipment is designed to provide constant amperage for more consistent penetration. A significant advantage of this mode is that changes in arc length, because of the welding variations, do not have a significant affect on penetration.
Many of the inverter power supplies enable the user to choose between CC or CV on the same equipment, providing the opportunity to evaluate both.
Pulse welding may have characteristics of CC or CV and should be considered when welding on thin sections.
Slow Run-In Start: This feature is desirable under circumstances that require precision starting characteristics to minimize start-up fusion defects and provide a starting profile that is acceptable when the weld overlaps at termination. It is also desirable to prevent wire-base contact problems (example, bird nesting) at the start of a weld when high feed rates are incorporated.
Hot Start: A hot start feature can minimize the tendency for incomplete fusion at the start of a weld, particularly on thicker sections used in structural applications. The hot start feature provides the opportunity to initiate the weld with a higher current density for a predetermined period before moving to the preferred welding conditions for the remainder of the weld. This feature can also be useful in corners and areas where a short, complete weld is required.
Crater Fill: This feature is designed to terminate the weld in a gradual manner by decreasing the welding current over a predetermined period as the weld is completed. The crater fill feature enables the weld to be terminated in a manner, which will prevent a crater from forming, and effectively eliminates crater cracking.
Burn-Back Control: This feature is desirable when the accurate and consistent positioning of the welding wire in relationship to the completed weld is required. When used with the crater fill option, the wire is effectively separated from the puddle and it leaves a sharp end in preparation for the next weld. It is particularly useful with those manufacturing procedures that require consistent restarting capabilities.
Other Equipment Features: There are other features which may be significant, depending on the application. Some of these features are: Electro Magnetic Braking, Visual Display of Amps and Volts, Pre and Post Weld Gas Flow, Water Cooling, and Wire Jog Buttons.