Chapter 8 Gas Metal and Flux Cored Arc Welding 207 Copyright Goodheart-Willcox Co., Inc. All drive rolls and wire guides are designed to properly align and center around the electrode wire. Figure 8-27A shows properly aligned drive rolls. If the rolls are misaligned as shown in Figure 8-27B, check to make sure rolls are properly installed and all wash- ers are in place. If the location of the inlet and outlet wire guides is adjustable, set the guides to be as close to the drive rolls as possible. Do not adjust guides so close that the rolls contact the guides. Adjusting the guides to be very close gives support to the wire and helps prevent wire feed issues. One problem that occurs occasionally during wire feeder operation is the wire getting jammed and form- ing a bird’s nest. A bird’s nest is a tangle of welding wire that did not feed properly through the rolls and into the guide tube. A bird’s nest can be caused by the following conditions: • Stubbing the electrode onto the base metal. This is caused by holding the gun too close to the work, using a voltage that is too low, or a wire feed rate that is too high. • Misaligned guide tubes and rolls. • A blockage in the cable or liner. Upper gear swings up to disengage gears Outer wire guide Knob to secure cable connection In and out adjustment for drive roll Drive housing Drive roll with drive gear behind it Wire pressure adjusting knob Inlet wire guide Pressure roll with gear behind it Miller Electric Mfg. Co. Figure 8-25. A two-roll wire drive system. The upper pressure roll can be pivoted out of the way when the wire pressure adjusting knob is released. Main drive gear Wire guides The Lincoln Electric Company Figure 8-26. A four-roll wire drive system. The parts are similar to a two-roll wire drive. The main drive gear is in the center below the two lower rolls. The main gear drives the gears behind the lower rolls. Pressure roll Drive roll In/out adjustment bolt Well-adjusted: proper alignment and pressure Wire too loose: adjust pressure knobs Rolls misaligned: check for missing spacer washer A B C Goodheart-Willcox Publisher Figure 8-27. Well-adjusted and misaligned drive rolls. A—Properly adjusted drive rolls. B—Rolls misaligned. Check installation. A spacer washer may be missing. C—Wire too loose. Increase pressure using the pressure adjusting knob(s).