Wire feeding issues are frustrating and my occur for all kinds of reasons for both solid (hard) and cored wires.  The good news is the problem is usually easy to diagnose and fix. Read on for common problems and solutions.

• WRONG DRIVE ROLL TYPE: Solid wires require smooth V groove rolls that exert considerable pushing force at two points on the round wire.  Cored wires require “knurled” V groove rolls that have little teeth that provide considerable pushing force but under much less tension.  Using the right “type” of rolls is critical.
• WRONG DRIVE ROLL TENSION: Too little tension and the solid wire will slip, the right tension the wire will likely feel correctly, too much tension and the wire will exit the drive rolls in a “pig tail” fashion creating liner resistance and feeding problems.  Cored wire with knurled drive rolls don’t require a lot of tension.  Too much and the wire will crush and stop feeding.
• CLOGGED LINER: The gun liner is a consumable part and needs to be changed out on occasion.  Why?  Wire lubricant, dust and dirt will accumulate in the liner over time producing feeding resistance and, eventually, wire slippage and/or drive roll bird nesting.
• GUN LINER CUT TOO SHORT: In this case, there is a space between the gas diffuser and contact tip where the wire has room to roam instead of moving in a straight line and the produced resistance causes feeding problems.
• OVERSIZED LINER: One size larger than the wire diameter generally doesn’t cause a problem and, in fact, may provide longer liner life.  However, in a highly oversized liner the wire will tend to “buckle” creating high liner resistance and feeding problems.
• OUTGOING GUIDE TUBE TO GUN MISALIGNMENT: That is, in damaged or out of spec drive systems, the wire exiting the guide tube may not line up with the gun liner.  In this, metal wire shaving are often seen below the contact point.  In any case, again, there is resistance on the wire from feeding properly.
• WIRE SPOOL SPINDLE TOO TIGHT: When the spool spindle is too tight, the drive roll tension has to be increased creating the problems described above in bullet #2.
• BAD WELD PROCEDURE AND/OR BAD GROUNDING: Both scenarios could result in a situation where the wire, upon contact with the work piece, does not immediately arc but rather stubs creating instant feeding resistance and bird nesting at the drive rolls.
• CONTACT TIP BURR: A tiny burr or speck of spatter on the contact tip can obstruct the easy feed of wire. In this case, change the contact tip.
• OVERSIZED/WORN OUT CONTACT TIP: As explained in BAD WELD PROCEDURE AND/OR BAD GROUNDING, if current cannot seamlessly transition into the wire because the contact tip in worn out, oversized or oblong, the wire will stub increasing the possibility of bird nesting.
• CHEAP WIRE: Not all wires are created equal.  Wires with cheap lubrication and a poor copper coating (flakes, clogging liner) and those with wide chemistry and diameter specs may be cheaper by the pound but can cause frustrating feeding issues and productivity losses.

Finally, if you have wire slippage but believe you have sufficient drive roll tension on the wire, it may be wise to find out what’s causing the resistance to feeding instead of further increasing the tension.  Disengaging the drive rolls and pulling the wire from the contact tip should be easy.  If it’s not, your liner may have a “kink” in it or be clogged and, therefore, should probably be replaced.