Author: Bob Page
Oftentimes, little but painfully annoying welding problems are caused by commonly overlooked culprits. Hundreds of times throughout my career I have observed frustrated welders that are achieving substandard welds because of what they believe to be, for example, a malfunctioning power source, “bad” shielding gas or a defective electrode consumable. Frequently, however, the source of the problem is easily and inexpensively solved once identified. Below are some simple fixes for some very common welding problems.
The Worn Out Contact Tip
Current is introduced into welding wire through an inexpensive copper contact tip that is considered a “consumable” part – meaning it degrades over time and needs to be replaced at some point. If current cannot seamlessly transition into the wire, an erratic arc characterized by spattering, wire stubbing and burn back may occur. Telltale signs that a contact tip is worn out and needs to be changed include an oval-shaped, instead of round, hole and/or spatter at the edge of the hole that is impeding the ability of the wire to feed properly. Depending on the amount of arc time a contact tip encounters, it’s generally good practice to change it on a daily, weekly or monthly basis. The benefits will outweigh the cost.
The Dirty Liner
The wire is guided through a MIG gun and cable by a replaceable steel liner. As this liner becomes contaminated with dirt and metal shavings, wire feed resistance will increase to the point where the wire will slip and potentially burn back to the contact tip as well as bird nest at the drive rolls. Assuming drive roll tension is adequate before the problem occurred, simply increasing drive roll tension is not the answer as a different set of unintended consequences may arise. To test the condition of the liner, disengage the wire from the drive rolls and pull the wire through the MIG gun. If you feel resistance, change the liner. The cost of the liner is marginal compared to the cost of downtime fighting wire feeding problems.
The Spatter Laden Gas Nozzle/Diffuser
For gas shielded wire processes the gas nozzle and gas diffuser, consumable parts like the contact tip and liner, will invariably accumulate with spatter over time. Removing spatter regularly from these parts will ensure proper and even gas flow. Spatter accumulation that is not removed will result in impeded gas flow and, ultimately, porosity that is at least unsightly and, at most, unacceptable and costly to remove. When the nozzle and/or gas diffuser have degraded to the point where they cannot reliably direct shielding gas onto the molten weld puddle, replace them.
The Wrong Drive Rolls
The solid wire should be run through V groove drive rolls and tubular wire must be run through knurled drive rolls. The solid wire that is run through knurled drive rolls (characterized by tiny teeth that promote feeding with minimal tension) will scar the wire resulting in premature contact tip degradation as well as metal flakes that will prematurely clog the gun liner. Using V groove drive rolls on a tubular wire will cause the wire to ultimately slip and burn back (if drive roll tension is low) or become crushed and not feed at all (if drive roll tension is high). Aluminum MIG wire should always be paired with U groove drive rolls.
The Flawed Welding Circuit
A stable arc requires a welding circuit where current flow is not hindered by high electrical resistance areas that cause a voltage drop and, thus, poor arc quality. These areas get very hot to the touch and are a dead giveaway of where your problem lies. If a ground clamp is not securely fastened to the ground cable, it will get hot. Tighten the connection. If a ground or weld cable is cut or frayed, it will get hot. Replace the cable. If a connection at the power source terminals is loose, it will get hot. Make the connection tight. If your cables are undersized, in diameter and/or length for the current/duty cycle you’re asking them to deliver, buy the right size cables. High resistance in the welding circuit should only occur at the arc.