While MIG welding is considered an easier process to learn and perform, it can be complicated at times because there is so much technology behind it. The wire feeding process alone requires several elements, which all have to be maintained for effective welding.
How smooth does your wire feed? How often do you inspect or change your gun liner, drive rolls or inlet guides? Do you have the correct drive roll style for the welding wire you are using? Do you check your drive roll tension setting? Are you having trouble with erratic arcs, contact tip burnback, birdnesting or excessive spatter?
While that might seem like a lot of questions, the answers are important. They are good indications of whether or not you should take a closer look at your wire feeding process.
Feel the tension
When there are issues in the welding process, many times it comes back to the drive rolls. Over-tensioned and misaligned drive rolls lead to consistency issues. The correct drive roll tension is critical to success.
First, though, make sure the correct style of drive rolls is being used for the type of welding wire. Four styles of drive rolls are available: plastic, V-groove, U-groove and knurled. The V-groove style is recommended for steel, the plastic and U-groove styles for aluminum and the knurled style for flux-cored wire.
Whatever the type of wire, it is critical that the correct drive roll tension is used. Too loose causes poor wire feeding and slippage. Too tight deforms the wire, which creates more dust and metal shavings in the wire feeder, gun and liner, leading to blockages.
Deformed wire affects feedability and wears out the liner and contact tip much sooner with saw-like edges as it passes through the liner and tip. After setting the drive roll tension, check to make sure this is not happening in your process.
As for hub tension, when mounting the wire reel to the feeder, tighten the hub enough to keep the wire from unraveling or overfeeding once you let go of the trigger.
As high-tech as welding equipment has become, it is still not an exact science on how to set drive roll tension. I was always told “tight, but not too tight, and definitely not too loose.”
There are few ways to set the drive rolls, but all are similar. The only truly unacceptable method to use is cranking down the tension setting knobs with pliers.
To correctly set tension, lay the gun out straight. Once the wire is fed through, take a wood block or metal plate and feed the wire into it. Once you get the drive rolls to slip, tighten the drive rolls a half turn more.
You can also feed wire into the palm of your welding glove if it is well padded. Just make sure there isn’t a really sharp point by bending the end of the wire over.
Once this is done, you should have the optimum drive roll tension needed to feed the wire. If you get to where you have to tighten more, there’s a good chance you need a new liner or drive rolls.
Using the welding wire that best suits the application is also important to good feeding. Good wire is consistent throughout the entire length of the wire and from batch to batch. The cast, helix and wire diameter are all critical to maintaining a good electrical connection with a smooth and consistent wire feed. It is also important to have a consistent chemical composition and lubrication of the wire.
If the diameter and feedability of the wire seem to be consistent, but issues still arise that you can’t pinpoint, don’t worry you aren’t going crazy. It may have to do with the chemical makeup and tolerances of the wire. At this point, bring in another wire and test it to see if the issues go away. If they do, you need to change the brand or grade of wire you are using.
The inside line
The gun liner is another key component of wire feeding. It is important not to have too large or small of a liner for the wire. This also causes feeding issues, causing excessive wear and premature failure.
The liner travels through the core tube of the gun and typically sits inside the welding diffuser. There are a few different ways liners are secured at the power pin. Some manufactures also have a setscrew in the diffuser/tip holder to make sure the liner does not shrink or stretch when twisted. But, this can also cause an array of issues if the screw is overtightened. If the screw is missing, note the hole is not meant to be an extra gas hole.
A quality liner is typically made from high-carbon steel wire. It is important that the liner coils are wound tight and to have good deflection and rigidity for when the gun is bent and twisted in different directions. It is also important for the inner diameter of the liner to be consistent throughout to keep feedability consistent. Nylon and Teflon liners are typically used for aluminum wire.
You can extend the life of the liner by blowing out the cable with compressed air to remove the dust and metal shavings. ATTC recommends doing it, at minimum, when you change the liner. But depending on your shop, and if you have access to it, we recommend doing it once a week. Another good time to blow out the cable is when changing the wire.
Blowing out and wiping down the drive rolls and wire feeder weekly is also recommended to control dust and shavings.
If cleaning out the cable and liner does not fix your wire feeding issue, the liner has probably worn out. The liner is a consumable item, so don’t hesitate to replace it.
When changing the liner, it is important to lay the gun out straight. Make sure the cable is not twisted. Having twisted cable when cutting the liner leads to cutting the liner at the wrong length. Keeping the liner off the ground, feed it through in short stokes making sure not to kink it.
Once the liner is fed through, use sharp diagonal cutters or welding pliers to cut the liner to the manufacturer’s recommended cut lengths. Make sure to remove any burrs as they can damage the wire.
If you are unsure of the length to cut, a good way to judge it is when tightening down the welding diffuser. You want to feel just a little bit of pressure from the liner pushing against the diffuser on the last thread or so. The reason for this is as you twist and move the cable, the liner, being a spring, can shrink or grow. If the liner is cut too short or long, it leads to an array of issues.
Here’s a tip
The wire feeding process finishes with the contact tip. A good tip, key to uptime and achieving consistent long-lasting welds, has smooth and consistent inner diameters. For different applications, such as robotic or manual welding, tips require certain inner diameters. This is important to keeping wire feeding smoothly with a good electrical connection.
When is it time to change a contact tip? When the wire starts to wander or you notice significant wear on the ID of the tip. You see what is typically known as keyholing.
Some contact tips can be rotated to create a new wear point to extend their life. Dual threads allow you to reseat the tip 180 degrees, and some threadless designs allow you to freely turn the tip and then secure it into place.
Make sure the tip is securely in place. A good securing method is important for any tip style. Use welding pliers and be careful not to scratch the OD of the tip, as this can attract spatter.
One issue with tips having too many threads is that it’s hard to get that tip out when burnback occurs. You will probably have to cut the wire at the back and feed the wire through again.
This is why some contact tip manufacturers have gone more and more to using 1/4-1 whole turns to remove tips, and some have gone to completely threadless designs.
One problem with a design where the nozzle secures the tip in place is the common, but incorrect, occurrence of welding front ends being used as hammers or just the rough environment in general. This can cause the piece holding the tip securely in place to come loose, which creates resistance and causes overheating, burnback and other feeding issues.
Several factors can affect and contribute to smooth, or not so smooth, wire feed. Set yourself up for success by keeping up on the basics, and making sure you have products that are meant to be used together.
Instead of working with suppliers that make and sell products based on price, partner with suppliers that sell products based on best practices and solutions. Doing so can bring a lot of value to your operation.
Not everyone needs the most premium product, but a product that is cheaper, in the long run, can end up being much more expensive. The key is to get the necessary product for the welding application to achieve the desired results.