While often overlooked, the consumables used in the MIG welding process play a key role in overall weld quality. Zeroing in even further, the contact tip recess, or the position of the contact tip within the nozzle, is key to producing a quality weld. The proper recess can affect productivity and help minimize the need for secondary operations.
Knowing when to use a recess, flush or protruding contact tip can help the welding process. A welder having trouble with excessive spatter, burnthrough, porosity or insufficient penetration should check the contact tip position. It could be an easy fix.
In recess
Contact tip recess is more or less what controls wire stickout, the length the wire extends from the end of the contact tip. The greater the recess, the longer the wire sticks out.
The most widely used type of tip, recessed contact tips are generally for higher heat applications. They are also used in applications where the nozzle may touch the workpiece, such as tack welding.
Recessed contact tips are used for spray transfer, pulse and other higher current applications (greater than 200 amps). The tip is typically recessed from 1/8 in. to 1/4 in., which makes for a wire stickout from 1/2 in. to 3/4 in.
A longer stickout gives the wire time to heat up before it is consumed by the arc. It helps smooth out the arc and stabilize the spray transfer. It also helps reduce the occurrence of burnback (where the wire melts and fuses to the contact tip), which helps extend tip life.
A recessed contact tip and longer wire stickout help to keep the tip away from the high heat of the arc. Heat buildup leads to an increase in electrical resistance in the consumables (the nozzle, diffuser and tip), which reduces the contact tip’s ability to pass the current to the wire. This poor conductivity can cause insufficient penetration, excessive spatter and other problems.
Contact tip recess affects shielding gas coverage, as well. A recessed contact tip provides consistent gas flow.
“When the contact tip positions the nozzle farther away from the arc and weld pool, such as with protruded contact tips that stick out of the nozzle, the welding area is more susceptible to airflow that can disturb or displace shielding gas without it getting to the weld,” says Travis Hall, Lightning MIG product manager, American Torch Tip Co. “Insufficient shielding gas coverage leads to porosity, spatter and insufficient penetration.”
Flush and extend
Flush contact tips have a shorter wire stickout, roughly 1⁄4 to 1/2 in., bringing the tip closer to the workpiece. These tips are used with short-circuit transfer and low-current pulse welding. The shorter stickout along with the lower voltages mean the wire does not heat up before it is consumed. This allows short-circuit transfer to weld thin materials without risking burnthrough and excessive spatter.
Protruding, or extended, contact tips typically have a 1/8-in. extension; wire stickout is 1/4 in. These tips are generally used when the welder needs to get into a tight weld joint, such as inside corners or deep and narrow V-groove joints. The downside is these tips increase the chance of arcing the tip to the workpiece, which could damage the consumables.
Overall, the general rule is the best wire stickout length is typically the shortest one allowable for the application.
“Everyone should use the shortest wire stickout they can in the application,” Hall says. “We always say some of it comes down to preference, but more so, you should use what is best for the application. Typically, the shortest one is the best one.”
It should be noted that the welder’s preference also plays a role. Welding problems can occur if the contact tip to workpiece distance is too short or too long. It’s important to hold a consistent distance for good arc stability.
“Some of it depends on the welder’s technique,” Hall says. “Wire stickout is affected by the nozzle depth, but it’s also affected by the welder’s hand and how far way he keeps the nozzle. Whether recessed or protruded, if someone is pulling back further than they should, the welder is making more wire stick out. Keeping the nozzle 1/4 in. to 1/2 in. away is recommended.”
Making adjustments
Two style of consumable are available – fixed and adjustable. Fixed nozzles, whether they are threaded or slip on, are meant for a specific recess. With adjustable nozzles, the welder can adjust the recess or stickout to what is needed.
Threaded nozzles offer a more secure connection, but are typically a little harder to remove. Slip-on nozzles are typically quicker to change and clean.
“We offer both styles, but in most cases, we recommend a non-adjustable recess,” Hall says. “With the adjustables, there’s a lot of room for error. Issues can come up because of inconsistencies through the shop when the welder adjusts the recess to his preference or needs by maneuvering the nozzle or tip to where he wants it (wrong or right) instead of using the best setup for the application.
“The threaded and fixed slip-on nozzles fit properly and match the recess,” he adds.
When it comes to the contact tip recess, the size and shape of the tip matter. For example, a large contact tip and a nozzle with a small opening where the tip is almost touching the nozzle can cause problems.
“Get a bit of spatter in there and all the sudden you’re touching tip to nozzle and arcing out,” Hall says. “The situation calls for a tapered contact tip.”
It can affect the gas flow, as well. With a protruding tip, for example, a smaller nozzle opening is better. A large opening provides too much area for the gas to go. It needs to be more focused.
Many other factors can affect the nozzle, diffuser and contact tip trifecta. One factor is the materials the components are made from. The materials alone can affect resistance to spatter and prevent heat buildup. Again, taking a look at these overlooked consumables might result in an easy fix for MIG welding quality issues.
