9.2 FCAW Equipment and Setup
Cameron Kjeldgaard
Components
FCAW is a semiautomatic process, which has an impact on the complexity of the equipment involved. With welding processes that are considered manual, the equipment is usually solid-state; that is, there are no moving parts. In contrast, FCAW always involves a mechanical wire-feeding unit that feeds the electrode into the weld pool with the touch of a button (or, more typically, a trigger), which sharply increases productivity and reduces the required operator skill. The trade-off is a higher initial investment in the equipment and a more in-depth troubleshooting process to solve welding issues.
The major components necessary for the FCAW process include:
- Welding power source
- Welding gun and cable
- Workpiece lead and clamp (ground cable/clamp)
- Wire feeder
- External shielding gas (needed for FCAW-G but not FCAW-S)
- Flux-cored wire electrode
The rest of this section explores these components in depth, with the exception of electrodes and shielding gas, which have their own devoted sections.
Welding Power Source
Welding power sources for FCAW may come in the form of transformer rectifiers, though inverter machines—which are capable of multiple welding processes—are becoming the mainstay of the modern welding industry. These welding machines may range in size from compact light-duty units, with the wire feeder and power source integrated into one unit, to large engine-driven welder generators. In industrial applications, an FCAW power source will typically be heavy duty, capable of operating at 100% duty cycle at currents of up to 400 amps or more.
Power sources for FCAW must be capable of producing constant voltage (CV) output, sometimes referred to as constant potential (CP). CV machines produce a volt-amp curve that is nearly flat as opposed to constant current (CC), which produces a steeply sloped volt-amp curve. What this means for you, the welder, is that the welding arc will have small voltage changes and drastic amperage changes depending on your electrode extension. Also, unlike CC, CV processes do not give the welder direct control over welding amperage; instead, the welding voltage is controlled directly at the power source while the amperage is dependent on the wire feed speed and electrode diameter. These three things—voltage, wire feed speed, and electrode diameter—must all be selected in conjunction with each other for a smooth welding operation. It should be noted that many modern welding machines are capable of producing either a CV or CC output, so you won’t necessarily be using or avoiding specific machines. Note that alternating current (AC) should not be used with wire-fed processes like FCAW.
When selecting the polarity at the power source, it is important to check the recommended welding parameters for whatever electrode you will be using. While some of the most commonly used FCAW electrodes for steel operate on direct current electrode positive (DCEP), many are