The electrode extended from the end of the contact tip to the arc is properly known as electrode extension. For short-circuiting metal transfer or GMAW-S, semiautomatic welding, the electrode extension should be held between 3/8”-1/2” (10 – 12 mm). For either axial spray or GMAW-P, pulsed spray metal transfer, the electrode extension should be held between 3/4” – 1” (19 – 25 mm). Maintaining the correct electrode extension is important to the uniformity of the penetration profile along the length of a weld, and it is considered to be an important variable for any GMAW procedure. AWS specifies winding requirements for GMAW solid wire electrodes. Cast and helix are two key requirements. Figure 31 shows a graphic depiction of cast and helix in a GMAW wire electrode. To measure cast and helix, a sample of wire electrode should be taken from the spool large enough to form a loop when it is cut from the package, and then left unrestrained on the floor. Cast is essentially the diameter of the loop (if the shape is an oval, it is the largest diameter circle that will fit within the oval). AWS requires the cast to be not less than 15” for 0.035” (0.9 mm) and larger diameter electrodes and not less than 12” for 0.030” (0.8 mm) and smaller diameters on all spool packaging larger than a 4” spool, [1 lb. and 2 lb. (0.5 and 0.9 kg) spools]. Helix is the rise of the wire electrode off of a flat surface.