Procedures & Applications
MMA Welding:
Efficient Joining of Metals
What is MMA welding, and where is this welding method best used? You can find the answers to these questions and much more here!
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MMA Welding
Efficient Joining of Metals
MMA welding is a job for professionals. Those who know how to do it benefit from an efficient welding process that offers a high degree of flexibility. Below, you’ll learn more about this popular technique, its advantages, and exactly how it works. We’ll also provide five helpful tips for putting it into practice.
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Suitable Materials
What is MMA welding?
MMA welding refers to a welding method in which a welding rod held in an electrode holder serves as the welding electrode. The arc forms between the welding rod and the workpiece. In this process, unlike in TIG and MIG/MAG welding, the rod gradually shortens during the process.
Therefore, while the distance between the welding torch and the workpiece does not need to be kept constant during MMA welding as it does in other processes, the electrode holder must be moved toward the workpiece accordingly. This often poses a challenge and requires many years of welding experience. The reason for this procedure is that the distance between the electrode and the weld pool must be kept constant. MMA welding is also often referred to in professional circles as
- Arc Welding
- Manual arc welding or
- known as electrode welding.
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Aluminum
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Arc Ignition & Electrode Guidance
How does MMA welding work?
To describe the process in more detail, let’s first take a closer look at the necessary tools and equipment:
A power supply, filler metal rods, and a welding or grounding cable equipped with an electrode holder are absolutely essential. Fortunately, with a properly coated welding electrode, no shielding gas is required, as the coating material forms a protective shell. Using a small inverter as a power source is common and convenient. Power can be drawn from standard building outlets.
The Welding Process, Part 1: Striking the Arc
The first step in MMA welding is to initiate contact ignition. This is done by creating a short circuit between the electrode and the workpiece. When the electrode is lifted slightly or tapped against the seam, the arc ignites accordingly. It is important to note that the ignition process must never take place outside the joint; otherwise, cracks in the material could result.
If you are using basic electrodes, it is crucial to allow an appropriate amount of time between ignition and the start of welding. Next, guide the arc back to the start of the weld. The first droplets usually appear porous; they will be remelted as the welding process continues.
The Welding Process, Part 2: Electrode Guidance
In MMA welding, the electrode is also held perpendicular to the sheet metal surface or at a slight angle and oriented slightly in the desired welding direction. As a rule of thumb, the visible arc length should be roughly equal to the diameter of the cored electrode. With basic electrodes, it is important to keep the arc very short. You can use the following formula:
Distance = 0.5 × core rod diameter
The welding electrode is moved to the starting point, but the arc is not drawn out. The width of the molten weld pool must be checked as the electrode is guided. It is important that the slag boundary line lies behind the weld pool. The distance can be adjusted by varying the welding current and the angle between the workpiece and the electrode.
The electrode must be moved safely at all times, with the handle pointing forward. The welder needs a good eye for the length of the arc, as keeping it very short is crucial in MMA welding. As the electrode gradually wears down, the arc becomes longer and longer. Once you see the end of the welding electrode, remove the slag accordingly, followed by cleaning the weld bead. Move on to the next electrode, strike the arc slightly ahead of the last weld bead, and guide it back to that point.
The parameters
MMA Welding:
Manual metal arc welding requires optimal current settings, with the current-carrying capacity of the electrode diameter playing a decisive role. Are you welding root passes or in the PF (upward) position? If so, stick to the lower limit values. For fill and cap passes, as well as for all other passes, it is best to use the upper limit values as a guide.
The higher the current, the faster the material melts and the shallower the penetration. Please note that the following parameters are merely guidelines. They may vary depending on the material, and the specific specifications of the electrode must always be taken into account. High-alloy steels, for example, require a lower setting than unalloyed steels because they have a high electrical resistance.
| ELECTRODE DIAMETER | RULE OF THUMB | CURRENT |
| mm | Factor x Ø | ampere |
| 2.0 | 20–40 × 2.0 | 40–80 |
| 2.5 | 20–40 × 2.5 | 50–100 |
| 3.2 | 30–45 × 3.2 | 96–144 |
| 4.0 | 30–45 × 4.0 | 120–180 |
| 5.0 | 35–50 × 5.0 | 175–250 |
| 6.0 | 35–50 × 6.0 | 210–300 |
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Here’s what you should keep in mind
What types of rod electrodes are used in arc welding?
The electrodes used in MMA welding consist of two components. The first is the core wire, which supplies material to the workpiece. Its composition depends on the type of workpiece being welded. If the workpiece is made of carbon steel, for example, the core wire is also made of mild steel. The core wire is the first part to melt during the welding process; the coating melts only afterward.
The electrode coating serves the following purposes:
- Protection against airborne contamination
- Protection of the core wire
- Cleaning the Base Material
- Increase the welding speed if necessary
In this case, the last point describes a high-performance electrode whose coating contains a filler metal in powder form.
Enclosure Types
The Type of Coating as a Decisive Factor
There are various types of coatings available on the market. The one you choose is critical to the welding process. The different types have distinct welding characteristics, which can affect, for example, the stabilization and ionization of the arc, the melting rate, or the protection of the workpiece against oxidation. The size of the droplets that pass into the arc is also particularly important.
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An Overview
Types of casings:
Coating Type B – Basic
- Very tough and firm
- Coarse droplet transition
- Highly recommended for steel construction, especially for high-strength steels
- Limited reignition capability
- Post-weld finishing is required
- Complex handling; requires a high level of expertise
Coating Type R/RR – Rutile/Thick Rutile
- Versatile use for various structural steels
- A Smooth Relationship with the Nahe River
- Good mechanical properties
- Good ignition and reignition characteristics
- Suitable for stapling
- Most suitable for laypeople
Coating Type RB – Rutile-based
- A Good Choice for Piping Construction
- “Intermediate Type” R and B
- Recommended for rising welds
- Very well suited for root attachment to the pipe
- Not suitable for stapling
Coating Type C – Cellulose
- Excellent for vertical seams
- Low slag formation
- Good mechanical quality
Coating Type RC – Rutile-Cellulose
- An All-Around Expert in Steel Construction
- Well-suited for welding vertical seams
- Relatively easy for laypeople to handle
Casing Type A – Sauer
- Very smooth transition between drops
- Low-viscosity weld metal
- Its use in emergency situations is strongly discouraged
- Lower quality than other types of coatings
How to Weld Even More Efficiently
5 Tips for the MMA Process
At this point, we would like to revisit, among other things, the topic of proper equipment for manual metal arc welding.
By choosing your equipment wisely, you can further increase the efficiency of the MMA welding process. Keep the following points in mind:
1. The Welding Mask
An automatic welding mask is a good investment. It comes with an auto-darkening visor. You can adjust the darkness level yourself in increments, which means you don’t necessarily have to take it off in between tasks. It can make your work significantly easier and help you work faster.
2. The Welding Machine and Its Features
When purchasing a welding machine, you should base your decision on the maximum electrode size. The smaller and more compact the machine, the better. This will save you a lot of time when you consider how long it often takes to move a large, heavy machine to different work sites multiple times.
Inverter-based machines, for example, are often a good choice. Thanks to their lightweight design, they are very productive. At the same time, they offer good welding dynamics, which allows for high-quality welds. If you use a power source based on inverter technology, you can also save electricity.
3. Useful Features
Purchasing certain additional features can pay off. For example, remote control is more than just a nice gimmick. It makes handling easier—especially during installation—and saves a tremendous amount of time throughout the entire work process. This leads to an increase in both productivity and the quality of work.
Another fact that is often simply overlooked is that a long welding cable further increases the total weight of the equipment. A hand cart can be a huge help here. People often don’t think of using one until the power source is too heavy to move manually. However, it’s worth reconsidering this if it makes the process more productive.
4. The Welding Electrode
Choosing the right welding electrode is often not easy. High-performance electrodes are generally highly recommended. In addition to a filler material, they usually contain iron in powder form. These materials fuse with the weld joint, resulting in increased efficiency.
5. The electrode holder
Choosing the right electrode holder requires a delicate touch. If it’s too large, the process slows down and access is also difficult. An electrode holder that’s too small, on the other hand, can be dangerous. It’s best to base your choice on the maximum current used in your facility; that way, you’ll generally make the right choice.
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What are the advantages of MMA welding compared to other methods?
One of the greatest advantages of the MMA welding process—in addition to the equipment’s light weight and compact size—is that it is not affected by weather conditions. MMA welding (M.M.A. MANUAL METAL ARC) can be performed both indoors in appropriately equipped spaces and outdoors. Especially in tight and confined spaces, it offers full accessibility—something that is often limited with other welding methods. Another benefit is that MMA welding does not require a gas cylinder, which you would otherwise have to carry with you at all times.
Conclusion:
MMA Welding Process
The MMA welding process is based on a method in which a welding rod held in an electrode holder serves as the welding electrode. The arc is formed between the welding rod and the workpiece. One of the greatest advantages of this method is its extreme versatility: successful welding can be performed both indoors and outdoors. Combined with the right equipment, this ensures fast and efficient work processes.
In terms of handling, however, the MMA process is often no walk in the park. It requires an experienced welder with as much prior experience in MMA welding as possible. Many companies therefore choose to outsource the work to a professional manufacturing firm.
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