Why is my MIG wire feeding improperly?

If your MIG wire isn’t feeding smoothly, there are a few key things to consider. This MIG welding troubleshooting guide will walk you through the most common MIG welding issues and how to resolve them.
 
Are you using the correct drive rolls for the MIG wire diameter and type that you’re running? Most all manufacturer’s drive roll kits will allow you to run two different wire sizes. If the drive rolls are flipped over to the wrong side for the wire you’re currently using, it may put too much tension on the wire causing it to deform and feed improperly.
 
Also, be sure you are using the correct type of drive roll for the wire. There are 4 different kinds of drive rolls which are used for different types of wire. Base your selection of drive rolls upon the following recommended usages: V grooved for hard wire such as AWS ER70S-6, U-Grooved for aluminum and other soft wires, V-Knurled for hard shelled cored wires, and U-Cogged for extremely soft shelled wires. 
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Are you using the correct liner for your MIG machine and does it need to be replaced? I always recommend to customers to change the liner once a year as normal maintenance. If you're in a shop that’s welding a lot, maybe a couple times a year is recommended. I often compare a liner in a MIG gun to an old drain pipe in your house. Over time, they begin to gum up with debris and need to be replaced. Shavings from the weld wire, dust and grime that's floating in the air around the shop gets pulled through on the weld wire. Since the gun is constantly being used in different positions, the liner could start to separate and break apart which may grab the wire as it's being fed through the gun causing problems.

As a test, you can loosen up the drives rolls and try to pull the wire out with a pair of pliers. It should pull out smoothly with minimal effort. If it requires a bit of force, it is time to replace the liner. For maintenance, you can invest in MIG wire cleaning pads which are little felt pads that are treated with a fluid that cleans the wire before it goes into the drive rolls. These will help.

Are you using the correct tension on the drive wheels? For most MIG machines, the manufacturers have listed what tension is recommended for the type of wire you’re running whether it be solid wire, flux cored, self-shielded or aluminum. If you have an older MIG machine that doesn’t list this, take all the tension off and slowly screw down the tension knob until the wire starts to push through the gun. To check the tension on your drive wheels, pinch the wire just before it goes into the back feed tube with some pressure. Once the tension is set properly, you should feel the wire wanting to pull through your finger grip. If the wire stops when you pinch it, screw down the tension knob a little more and repeat this process.

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Are you using the correct contact tip for the MIG wire you are running? Wire that’s .035 diameter usually won't fit through a tip that's made for .030 diameter wire. However, I am often asked “If I have an .045 tip, can I run my .035 wire through it?" The answer is that you shouldn't. They are called contact tips because this is where the welding wire makes its best electrical contact to create your arc. If the tip is too large, the wire could bounce from side to side, which causes an erratic welding arc. Not what you want. Size tips accordingly.     
                
Are the wire guide tubes clean? 
Nothing magical here. These come with the machine and are usually brass or plastic. They are installed where the wire goes into the drive roll and where the wire goes out of the drive roll into the gun. If you have a four roll drive system, there will be one between the drive rolls as well. Just make sure they're clean of debris (the same stuff that could be in the liner) and make sure that the wire hasn't worn a groove into one side. If so, you can spin them around or replace them. 
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Do you need to replace your welding wire? 
If the wire has been sitting out, uncovered and unused, for quite some time it may have rust on it "copper coated solid wire." If this is the case, it's best to throw the wire out and get yourself a new spool. You can find welding wire shelf life by searching it on the web.

Proper maintenance and selecting the right consumables can make all of the difference to create a good MIG weld. 

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Brant hancock

AWS Certified sales associate with over 20 years experience in the welding industry
Account Manager at Earlbeck Gases & Technologies