Troubleshooting – MIG Welder Not Penetrating

nice penetration mig welding

For beginners, MIG welding is one of the most common welding processes. However, just like any other welding process, MIG welding has its own problems or complications. That is why there is no reason to let common issues affect you or slow you down. In fact, with some troubleshooting capabilities and a bit of knowledge, you will be able to detect the problem and find the best solution with ease.

One of the common problems that you may encounter is that your MIG welder is not penetrating the base metal enough. Actually, this problem may affect your whole learning curve if it is not resolved as soon as possible.

If you have encountered this issue then keep on reading. In this post, we will discuss some of the common causes of why your welder might not penetrate the workpiece properly.

The Basics

Get rid of impurities

Most of the time, porosity is caused by a dirty surface. When the base metals are not cleaned properly, the welder just can not penetrate properly, and on top of that, it will create porosity in your bead, which will weaken the weld even more. I have a whole article about porosity in welding and you can read more about it here.

With this in mind, make sure you prepare your material to get rid of all excess dirt, rust, oil, etc.  MIG welding is actually a sensitive welding technique to bond metals that are contaminated. Thus, make sure that you’ve sanded, cleaned, and wiped your metal so that the permeability will be minimal. By doing so, your MIG welder will more likely penetrate, but it is still the tip of an iceberg.

Set your gas flow rate

If you want to enhance your welding quality one of the fastest ways that you can do is to ensure that your gas is set to the correct amount.

Even so, welding gas is usually measured in ft.-lbs. As a piece of advice, make sure to set your MIG welder to around 20-25 cubic feet per hour.

Setting your welding gas can be done by modifying the flow meter of the MIG welder. Nevertheless, if you want to check the output levels, simply follow the steps below.

  • First, turn the wire speed down to check the level of the gas.
  • Then hold the weld gun’s trigger. By doing this you can see where the indicator is exactly while you are welding.
  • When you have an idea of how much is coming make sure to adjust the level between 20-25 cubic feet.

Another common problem that comes to mind with gas regulators is the fact that a lot of times welders forget to even open the gas bottle, and if you are just a novice, you can weld for hours wondering what is wrong without realizing it.

As an extra tip, using a pure CO2 will give you some extra penetration. I have two more posts that I would encourage you to read:

Slow the welding speed

If your MIG welder is not penetrating consider slowing your welding speed instead of pushing the weld too fast. If you try to move a little slower, make sure you slow down your wire feed speed as well. It gives you more time to move along the joint, thus it will become hotter. Hotter base metal equals better penetration.  

Set Wire Speed

The next thing that you need to consider if your MIG welder is not penetrating is how rapid the wire speed is. If your wire speed is way too fast, the welder will produce more popping sounds.

I will not stop here for very long since I already mentioned it, but it is still important part to keep in mind. If you are interested I have a table of right settings including wire feed speed, volts, and amps here.

Run multiple passes

Now, if you are welding very thick materials with a welder that is not right for the job, you can get a little extra penetration by using a bevel joint and running multiple passes. Bevel itself helps you to get the bead deeper into the metal, but running multiple passes will help the penetration at some level. Running multiple passes, the base metal is already ”preheated” which will give you naturally better penetration. As we already mentioned, the hotter the base metal the better the penetration.

If you can not run multiple passes, consider actually preheating the base metal with a torch. It will surely help.

Why MIG Welder Might Not Penetrate Base Metals – The more complicated reasons.

  1. Make sure that you have enough juice. Meaning, if you use an extension cord, make sure you use a proper one. It is better not to use one at all. If possible plug the machine straight into the wall. If you just bought a new welder, or you are somewhere you have not used a welder before, make sure that the wires in the building are suitable for welding. The ladder is more common than you might think.
  2. Make sure you have a proper ground connection. It should be intuitive already that you clean the spot where you attach the ground clamp. If you have done that but still no penetration, try to attach the camp closer to the spot you are welding. And that for a very simple reason- for example, if you are welding something more complicated than just two metal plates then the current might not move well enough trough the workpiece to create a proper arc. I hope it made sense, but to give you a simple example – if you are welding (repairing) a car exhaust that is still fitter to the car and you attach the clamp to the rear axle you might not get an arc at all. The reason is that the exhaust is pretty much isolated by the bushings and rubber clamps from the car chassis.
  3. Make sure that you have proper filler wire. If you are welding thick materials, you need thick wire as well .023 will not penetrate ½ thick material. And definitely don’t try to use regular MIG wire on the gas-less machine. Make sure it is set up properly.
  4. Last but not least, the wire itself can be ruined by oxidation, which depends on how you stored the wire. If you are using an old wire or a wire which came with the machine when you bought it, I would recommend you to buy a new roll. Especially if you think your settings are on point and you still can not get decent bead.
    That is the one I use, and it is really good and well worth the money in my opinion.


No matter what welding process you are using make sure that you are always getting good weld penetration, especially if you start doing some serious welding jobs like repairing an engine mount. Definitely practice and fine-tune the settings on a test scrap metal piece before taking on those kinds of projects. That is for your own safety.

I believe that I provided most of the important stuff in this article to help you get up and running again.

If you have any other questions, comment below!

Categories MIG