In this guide, let us see some basics of MIG Welding, look at the essential equipment for MIG Welding, and also see how the position and direction of the welding torch can impact the penetration, bead, and weld profile of the welding.
A Brief Note on MIG Welding
Gas Metal Arc Welding (GMAW) is the “technical” name of the more popular term MIG Welding. It is an Arc Welding Process that fuses metal pieces with the help of an electric arc. MIG Welding creates an arc between an electrode in the welding torch (or welding gun) and the workpiece. As the electrode melts and becomes a part of the weld pool, we call it a consumable electrode. So, in the MIG welding process, you need a continuous feed or supply of the electrode (which is usually in the form of a thin wire). The name “MIG” came from the fact that this welding process uses an inert gas to shield the molten pool from surrounding contaminants. Initially, Argon and Helium (both of them are inert gases) were popular choices for shielding gases. But later, Carbon Dioxide (CO2) in combination with Argon or Helium also became quite common. Hence, the Americal Welding Society (AWS) renamed it Gas Metal Arc Welding (GMAW).
Important Components of MIG Welding
The four main components of a typical MIG Welding setup are:
Welding Machine (Power Source) Welding Torch (Welding Gun) Wire Feeder Gas Tank
MIG Welding Machine consists of the power supply. One electrode comes directly from this machine and we attach it to the workpiece. A wire, which comes from a wire feeder with other supporting mechanisms, is fed through the welding gun. Speaking of a welding gun, it carries the electrode wire and also has the system to apply the shielding gas through a nozzle surrounding the electrode. The welding gun has a grip/handle for the welder or operator to hold it and move it around the workpiece.
Travel Angle of Welding Gun
The travel angle of the welding gun relative to the welding joint has a huge impact on the depth of penetration and the width of the weld bead. Depending on the angle the welding gun makes with the workpiece and the direction it travels with respect to the molten pool, we have three basic techniques.
Forehand Backhand Perpendicular
Let us now see about these techniques.
Forehand
When you hold the welding gun at an angle and move it over the weld pool (finished part), this technique is known as Forehand Welding. As you are essentially pushing the welding gun (or the electric arc) away from the weld bead, we sometimes call this the “Push” technique. In the Forehand Welding technique, the welder can clearly see the metal joint but not so much of the weld pool. This technique will usually produce a wide weld bead with shallow penetration.
Backhand
When you hold the welding gun at an angle and move it away from the weld pool (finished part), this technique is known as Backhand Welding. In this technique, we are essentially pulling the welding gun towards us and over the joint. Hence, we sometimes call this the “Pull” technique. In Backhand Welding Technique, the welder has clear visibility of the weld bead but not so much of the metal joint (yet to be welded). The pull technique often results in a narrow weld bead with deep penetration.
Perpendicular
When you place the welding gun (or the electrode wire to be specific) at a 90° angle to the workpiece, then the technique is known as “Perpendicular” or “Vertical”. You can move the welding gun along the welding joint in any direction as long as it stays perfectly perpendicular to the surface of the metal. The perpendicular or vertical welding technique offers a decent balance between forehand (push) and backhand (pull) techniques. The weld bead isn’t too wide and at the same time isn’t too shallow.
MIG Weld Push or Pull
Now that we have seen the basics of MIG Welding, its operation, equipment, and also the angle of the welding gun, let us understand the differences between Push and Pull welding techniques.
The “Push” Technique
Let us begin with the Push Welding technique. In this, you hold the welding gun over the weld pool and push it away from you (over the molten pool). You can clearly see the joint on the workpiece (the part of the workpiece that hasn’t been welded yet) but you cannot see the weld bead (the finished part). The penetration profile of the “push” technique isn’t that deep. You will end up with a shallow penetration of the weld bead. Also, the width of the weld seam is quite wide. As the depth of penetration is not deep, the strength of the weld isn’t too strong in general. But the appearance of the weld contour is very good. There is also a chance of weld splatter while pushing the welding gun. When you apply the Push technique, it spreads the molten pool over a large surface area and creates a wider pool. As a result, the strength of the weld in some applications is much stronger than it appears. You can constantly see the workpiece you are welding. This is important in some situations where the shape of the workpiece is odd (or you have a workpiece that has a lot of curves). When you are working with certain metals such as aluminum, the push welding technique is the only way to go if you chose the MIG Welding process.
The “Pull” Technique
In the Pull Welding Technique, you hold the welding gun and pull it towards you away from the weld pool. Here, you can clearly see the weld bead (the molten pool of weld) as you weld the workpieces. This gives the welder an idea about the quality of the weld, the formation of welding cracks, or any irregularities right as they are welding the metals. The downside of the pull technique is there is no clear vision of where you are going i.e., you cannot clearly see the workpiece that hasn’t been welded yet. Coming to the welding profile, the Pull technique produces a narrow but very deep weld bead. Even with a narrow weld pool, as the bead has deeper penetration, the final weld has very good strength. The overall aesthetic contour of the pull welding technique might not be very good. You might also need some scraping or polishing after the weld to give it a clean look.
When to use MIG Weld Push vs Pull?
Now comes the controversial part i.e., MIG Weld Push or Pull technique, which is better? The simple answer is it depends. There is no such thing as “this is better or worse” as both push and pull techniques have their fair share of pros and cons.
If You Are a Beginner
For experienced welders, the situation is much simpler as they will be familiar with both techniques and can easily adapt to either one depending on the nature of the job. But if you are a beginner, then you could start with the push technique as you can always see the workpiece and the path you are about to travel. Even though you cannot see the weld pool, you will stay on course without deviating from the path. Once you are comfortable with the push technique and get a good grip on understanding the path of the workflow, you can get into the pull technique. In doing so, you will be able to easily and instantly evaluate the shape, structure, and contour of the weld bead. If you need to make any corrections to the weld bead, you can do it immediately. That said, there are some situations where one technique works better than the other. For instance, if you are welding in a straight line and don’t need to constantly look at the workpieces or the path, then the “Pull” Welding Technique is a better choice. But if you are working with a weird shape or a tricky path, then you might always need to keep an eye on the path. This is where the “Push” Welding Technique seems appropriate.
If Strength is Your Priority
The next important factor is weld strength. From the above discussion, it is clear that the Pull or Backhand Welding Technique produces a stronger welding joint than the Push or Forehand Welding Technique. So, if strength is your priority, then you might have to choose the Pull technique.
Other Cases
If you are using a flux core electrode with your MIG Welder, then you might want to pull rather than push. This is because pushing a flux core might create a slag as we are forcing the slag into the molten pool. When working with certain metals such as Aluminum with a MIG Welding Machine, you need to be aware of the effect of pulling vs pushing. When you Push the MIG Welding Gun on Aluminum, you are offering a better flow of shielding gas as the direction of the nozzle and the weld pool are the same. If you pull, the weld area might not receive sufficient shielding and it can result in welding pores and cracks. In some situations, you might need to use either of these two techniques. For instance, if you are working in a situation where you don’t have the room or angle to push (or pull), then you have to adjust yourself and proceed with the pull (or push) technique. There are situations where you might have to use both techniques together. Push for normal welding but pull to increase the strength of the weld (for example, in a joint). You can also apply both techniques on the same weld, once the pull technique to get deep penetration and once the push technique to widen the bead.
Conclusion
MIG Welding is one of the most popular and widely used welding techniques in industries, manufacturing, automobiles, etc. Even with the popularity, there are some things associated with MIG Welding that is still up for debate. Of course, we are talking about MIG Weld Push or Pull techniques. While we can apply both these methods, beginners find it very difficult as some say pulling is better while others say pushing is. In this guide, we saw the basics of MIG Welding, its process, and the equipment. After that, we saw the working of both Push (Forehand) Technique and the Pull (Backhand) Technique. We also saw their advantages and disadvantages. To conclude, with MIG Welding, if you “Push” the welding gun, you will get a shallow but wider weld bead. Its strength isn’t great and you cannot see the weld pool but only the weld path (the workpieces). You will get a clean and good-looking weld pattern. Although, you have to worry about weld splatter. But if you “Pull” the welding gun, you will get a deep yet narrow weld bead. The final strength of the welding process is excellent although the weld might not look good. You will always have a clear visibility of the recent molten pool but you cannot see the path (the workpieces) very clearly. Comment * Name * Email * Website
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