Mig Welding Troubleshooting – Most Common Problems and Solutions

Mig Welding TroubleshootingMIG welding is one the most frequently used welding techniques as it is simple yet effective to satisfy one’s basic needs. Just like every other process MIG welding has its own problems and difficulties. Yet, having an upper hand in the problems that arise to a MIG welder and troubleshooting them with ease will help you running the machine like a beast.

Let us now look at some of the basic problems that an MI welder might get during MIG welding troubleshooting. After all, having the best knowledge of welding techniques isn’t everything that one must know.

By following this content, you will get a brief idea of how to maintain your MIG welder and also prevent before you may encounter any kind of problems in the device. Regular cleaning of base metal, maintaining travel speed, keeping an eye on polarity, and electrode replacement will help you with the basics of troubleshooting.


  • Porosity
  • Undercut
  • Spatter
  • Deformation
  • Cracks
  • Incomplete Penetration
  • Slag
  • Incorrect Wire Delivery
  • Birdnesting


  • The capturing of gas in small packets in the weld or metal that appear as bubbles (or) ‘pores’ is termed as Porosity. It can occur on the surface or at a particular point or all along the full weld causing the production of a weaker weld.
  • The main causes for this issue are the presence of air molecules held between the weld/metal particles, improper shielding gas, or else the presence of moisture and rust on the surface of the metal. This can relate to an overall “improper” surface for welding.
  • Shielding gas must be adequately supplied by analyzing the regulator and gas nozzles. Moreover, check the hose and nozzles for any leaks beforehand.
  • It can also occur due to the supply of incorrect shielding-gas in wrong quantities.
  • The presence of contaminants like Sulphur and phosphorous in metals and welds makes this an easy option to execute.


  • The ideal filler metal and base metal must be used for the shielding gas that is supplied in the right amounts.
  • An accurate amount and quality of the anti-spatter are necessary to avoid porosity in the weld puddle in the near future.
  • Instead of or re-making or using freshly prepared welding materials, deoxidizers can be applied on these impure metal surfaces to remove the contaminants like moisture, rust, Sulphur, and phosphorous.
  • If none of these options work, we have the only option of re-baking the entire weld again following strict preventive measures.


  • An undercut is a condition where a weld metal is unable to fill the gap between the welding metals and it, in turn, weakens the toe of the weld. Moreover, it increases the chances of cracking and further damage to the metal.
  • This generally occurs when the voltage supplied is too heavy.
  • Even if the electrode is too large in diameter or the incorrect application of the angle may lead to this issue.
  • Holding a vertical plate while welding a horizontal weld is another major cause of an undercut that is heavy.


  • As mentioned earlier, heavy arc voltage isn’t necessary. Hence, reducing the arc voltage as per requirement is advisable.
  • The travel speed of the weld must be reduced to fill all the unfilled areas of the base metal.
  • Maintain an angle between 0 to 15 degrees of the welding puddle of the arc to avoid undercuts during a MIG welding process.
  • Make sure the gas pipe nozzle is clean and the size of the electrode is not larger than required.


  • The presence of excess molten material as droplets on the surface of the welding arc is known as ‘Spatter’. This is generally caused by the weld puddle’s explosion of the molten material over the weld bead.
  • When this molten material cools down to form a non-uniform layer on the metal, it destroys the appearance of the weld.
  • It can also occur due to improper quality and quantity of the shielding gas supplied. Moreover, a change in the polarity of the electrodes may also cause such a spattered scenario.


  • Reduce the size of the welding wire extension
  • Reduce the weld voltage as much as possible to meet the requirements.
  • Wire-speed must also be kept nominal to accurately weld the members properly without any spatter.
  • Make sure the polarity of the electrodes is correct and the gas nozzle is cleaned often to avoid any contamination.


  • The muffler used in MIG welding often undergoes heavy stresses and eventually thermal deformation overtime.
  • Hence, the SYSWELD software can be used to identify these kinds of deformations before starting the welding process and undergoing it.
  • Once the melted weld materials are cooled down and hardened, a change in the overall shape and structure of the metal is known as a ‘Deformation’.
  • It may also occur if there is insufficient clamping from both of the sides of the finished piece and the presence of a lot of thin beads in the weld.


  • Over welding must be avoided to prevent any kind of deformation.
  • Planning the welding sequence before starting the process will give us a clear idea about all the neutral axes and welding angles.
  • Welding from both sides of the material and clamping them around all the sides will also help prevent these kinds of deformation.
  • Welding from the center and out in all the possible opposite directions is necessary to reduce the chances of random hardening and deformation.


  • A crack in any material is always considered a defect.
  • Generally, a small crack tends to widen up to form a larger one that eventually makes a hole or breaks the metal completely.
  • Crack repair is very hard in the welding process, it is better to prevent it than repair it later on.


  • Cleaning and deburring the edges of the metal plates can help with the prevention of cracks.
  • Clamping the side edges after proper heating of the metal plates can also prevent cracks in the metal welds.
  • Provide sufficient heat to the weld before the welding process.

Incomplete Penetration and Fusion

  • When the end of the arc weld wire melts due to a short circuit, and sometimes when the weld is unable to fuse on one side is said to be ‘Incomplete Penetration (or) Fusion’.
  • The improper fusion between the base metal and weld metal is caused due to less amount of heat supplied by the torch on the welding material and at the junction of the two metals.


  • Maintaining a proper welding profile for penetration and arc material characteristics is important.
  • Keeping a record of the wire feed speeds and also drastically optimizing the travel speeds are good measures to prevent it.


  • The presence of a mixture of unwanted non-metallic particles in the weld is termed a ‘Slag’.
  • Slag inclusions do not allow the penetration on the weld between the metals.
  • It causes distortions in the joints, poor welding structures, and much more.


  • Make sure that the weld beads are smoothened and reduced fusion to reduce the number of pockets formed that hold the slag.
  • Applied arc voltage must be monitored from time-to-time and travel speed should be maintained to avoid slag formation.
  • Try to avoid the rapid cooling of the weld pool as it might also attract more amount of slag particles.


  • The hindrance of a wire from being fed and used in the welding process due to another wire is termed as ‘Birdnesting’.
  • This is a type of wire feed issue that might have an adverse effect on the welded metal.
  • ‘Burnback’, is another issue where a wire melts back to the feed and fuses with the contact tip of the weld. It hinders the welding process from continuing properly.


  • Increase the wire feed speed can fasten the weld to the exact mid-joint of the metals.
  • To minimize the chances of birdnesting, try to decrease the distance between the wire feeds by using short cables for the welding process.
  • If burnback has occurred once, replace the nozzle tip with a new one.
  • Do not use incorrect diameter (or) wrongly trimmed liners.

Incorrect Wire Delivery

  • When wire delivery to the contact tip is not accurate enough it may lead to some damage to the wire. This may cause a chattering (or) hissing sound in the gun cable that might be the indication of a faulty wire delivery.


  • An ideal welder must make sure that the contact tip of the gun and the gun cable is functioning properly.
  • Drive rolls and guide tubes must be placed close to one another.
  • Also, the gun liner must be accurate to the size of the wire that is currently being used for welding.

Stick Welding

Stick welding is also known as ‘Shielded Metal Arc Welding’ (SMAW). The electrode that we use in this process is generally called a ‘stick’. Here, the welding machine is connected to an AC (or) DC power supply. The electrode provides filler metal for the joint between the two metals by forming an arc.

It is widely used in repair and maintenance factories.

Basic Qualities

  • Current Setting: As positive electrodes with extensive penetration of metals, the applied current in amperes must be minimal. While for negative electrodes, a higher range of current density can be applied to the metals at the correct position and penetration angles.
  • Electrode Size: High penetration metals require large electrodes functioning at high voltages. Use 5/32 inches electrode size for low hydrogen metals.
  • Arc Length: The length of the arc is the determining factor of the speed and efficiency of the welded metal that is produced without any distortions.
  • Arc Angle: The penetration angle of the arc weld must be in the range of zero to 15 degrees.
  • Cleanliness: Reuse of an electrode is not advisable for the next welding process. Removal of dirt, dust, moisture, and Sulphur is advisable before starting the weld of the base metal.
  • Supplies: Make sure you have an adequate amount of supplies like sandpaper, electrodes, constant power supply, hammer, and angle grinder.

Watch Video: Most Common MIG Welding Mistakes


Hence, appropriate knowledge attained about the problems arising in MIG welding and learning the techniques to troubleshoot them will help you reach a point where you can weld perfectly shaped metals according to the design and detailed requirements. Sound knowledge about preventive measures will help you solve these issues quickly and efficiently.


What’s wrong with my weld?

There could be several issues that could lead to a wrong weld such as:

  • Damaged Drive Rolls: The drive rolls have the tendency to get damaged quite soon and they need to be replaced often for the proper functioning of the weld.
  • Birdnesting: Hindering the wire feed that halts the welding process due to the tangled wire.
  • Impurities: Certain substances like Sulphur, phosphorous, rust, moisture, and so on present on the surface of the weld/metal will lead to a defective weld.
  • Shielding gas: The insufficient supply of shielding gas contaminates the weld puddle which in turn leads to deformation.
  • Burnback: Avoid melting the wire by not placing the gun too close to the workpiece.

Why is my weld spattering?

The major issues that lead to a weld spatter are:

  • Cleanliness of base metal
  • Incorrect arc angle
  • Unoptimized wire feed speed
  • Heavy supply of arc voltage
  • No shielding gas supplied

How do you fix a welding burn?
A burn may cause the formation of a hole or a crack in a welded metal. Hence, it is advisable to take special care while doing the preheat, post-heat, and while heating the filler alloy metal. Try to use copper as a support for the back of the metal. Complete the process using rust-oleum.

How to repair welding defects?

  • Remove the leftover wire from the gun and replace it with a new one keeping it as much straight as possible.
  • Make sure the length and diameter of the wire you use are accurate enough for your model.
  • The drive rollers used for the wires should not hold the wire too tight or too loose.
  • Make sure enough amount of shielding gas is supplied to the weld paddle without any hassle.
  • Optimize and maintain the wire speed throughout the welding process.
  • Keep a check on the cleanliness of the nozzle and contact tip every time you leave the welder.