The popularity of semi-automatic welding is increasing daily. This trend is not coincidental. Among the most important welding technologies, MIG/MAG is characterized by its high productivity. Master welders appreciate its ability to quickly produce high-quality joints, while beginners are attracted by the automatic wire feeder, which allows them to “get hands-on” more quickly and learn to weld relatively easily.

Is it worth buying a semi-automatic welding machine? If so, which device should you purchase? In the article “Semi-automatic MIG/MAG welding – what is it and what is it used for,” you can read more about the different types of equipment and materials for this technology. Here, we will only consider the devices that can be used in a small workshop.

First of all, it should be noted that MIG/MAG equipment is generally not characterized by simplicity and mobility. It includes:

  • Welding power source;
  • Wire feeder;
  • Torch with a tubular bag;
  • Coil with electrode wire;
  • Gas supply system (gas cylinder, reducer, hose, etc.);
  • Personal protective equipment.

Therefore, it’s important to consider the tasks ahead. This will help you select all the necessary components as accurately as possible. Let’s start with the most important thing – choosing a semi-automatic machine.

By Design

Semi-automatic welding machines can be double-walled, with the wire feeder and torch separated from the welding power source. They are often installed in production facilities. For a home workshop, it’s better to choose a monoblock. This is a compact semi-automatic inverter that combines three main components in one housing: the welding power source, control unit, and wire feeder. The inverter ensures stepless adjustment of current and inductance for various types of welding, while the electronic board ensures coordinated operation of the power source, and the wire and gas feed mechanisms to the torch.

Functionality

In addition to MIG/MAG, semi-professional machines can also support other welding techniques. These are limited but can include several processes: Argon arc (TIG), manual metal arc welding (MMA), cold (COLD) and pulse welding (PULSE), and sometimes air plasma cutting (CUT).

If you intend to use different methods of metalworking, check the availability of the modes you need. With pulsed current, for example, you can join difficult-to-weld metals such as aluminum and stainless steel more successfully. The MMA mode gives you the opportunity to get back to good old gasless welding.

Technical Characteristics

To make the most accurate selection possible, you should try to adequately assess the intended work and the conditions under which you will be welding.

Welding Amperage

When selecting a semi-automatic machine, pay attention to the limit values for the amperage – max and min. You can use the maximum value to estimate the maximum thickness of the parts to be welded. The minimum value indicates how thin the metal can be welded without the risk of burning or deforming the workpiece.

For example, for welding products made of sheet steel, you will need only 10-20 A, for parts with a thickness of 1.5 mm – about 70-80 A, and for metal with a cross-section of 3 mm – 120-140 A. For this range of tasks, semi-automatic machines with a current range from 10 to 145 A are well-suited. However, if you do not exclude the welding of products with a thickness of 5 mm, it is better to purchase an inverter with a wider current range, where the maximum indicator is at least 200 A.

Open Circuit Voltage

This is the standby mode when the device is switched on but the arc is not yet struck. At this time, the device maintains a certain current value in the range of 40-90 V and is ready to ignite the arc when the wire touches the metal surface. The higher the value of the quiescent current, the easier the ignition will be. A quiescent current of 30-40 V is sufficient for a home workshop.

Percentage of Payload (PU)

This value is also referred to as the duty cycle. It indicates the duration of continuous operation of the machine at maximum current, based on a 10-minute cycle. When selecting a model, you can estimate the welding intensity. For example, a PU of 60% means that you should take a 4-minute break after 6 minutes of work. Normally, a single seam at home rarely takes longer than 4 minutes. Please note that the switch-on time increases up to 100% if the current is reduced.

Power

This parameter specifies the power of the welding machine. The higher the power, the more extensive the welding work that can be carried out. For example, to weld a frame for a greenhouse in the countryside, an inverter with an output of up to 3.5 kW is sufficient. To connect larger parts (e.g., heating pipes), you will need a more powerful model (5-7 kW). When selecting, it is important to consider the power supply in the room where welding is to take place to avoid overloading.

Mains Voltage

Various models of semi-automatic welding machines can be designed for three-phase or single-phase networks. Machines with a maximum welding current of up to 250 A are suitable for 220 V networks. However, it should be borne in mind that voltage dips may occur, as is typical in country houses or garages. In these cases, an inverter that allows welding at 130-160 V is the best choice.

What Else Do I Need to Pay Attention to?

Electrode Wire

In semi-automatic welding, a solid wire is usually used. The diameter and composition of the wire are selected according to the thickness and type of metal to be welded.

However, some semi-automatic welding machines can also work with cored wire (with different compositions). In this case, MIG/MAG welding is possible without shielding gas. This option is particularly practical for those who work at height, in open spaces, or simply do not want to connect a gas system. In the characteristics of the semi-automatic machine, the electrode diameter (max/min) corresponds to the power and operating current range. You can therefore also use this parameter to assess the capabilities of the model.

Torch Cooling

Welding torches supplied with semi-automatic welding machines are, in most cases, self-cooling. They are cooled by the ambient air and, at the end of the process, by the shielding gas flowing through them. This is sufficient for short welds. However, if intensive welding with long passes is intended, it is better to use models with a water-cooled torch.

Degree of Protection

The electronics of inverters are sensitive to dirt and moisture. The degree of protection of the inverter is indicated by the abbreviation IP with a numerical index. This index signifies that the device is protected: IP21 – against vertically falling drops; IP22 – against drops falling at a 15° angle, and IP23 – against drops falling at a 60° angle. If welding is planned in a dry and clean room, and not outdoors or under a canopy, it is not worth paying extra for the degree of protection.

Control Features of Semi-Automatic Machines

Inverter semi-automatic machines are typically equipped with an intuitive control panel that includes a practical system of settings, indicators, and displays. If you’re beyond the beginner stage, a semi-automatic machine with manual settings is suitable for you. With these, you can set all the welding parameters yourself, depending on the task and your own experience.

If you’re just learning to weld or prefer to rely on electronics, choose a model with synergic control. In this case, you only need to set one parameter in the settings (e.g., the wire diameter), and the machine will automatically set all operating parameters.

Additionally, for each mode supported by a particular machine, there may be automatic options that facilitate and improve the welding process. For example, two torch modes for MIG/MAG welding are 2-stroke and 4-stroke. The first mode is sufficient for small parts. The 4-cycle mode is very practical for long joints as it enables continuous welding without having to hold down the button on the torch.

In TIG mode, the non-contact high-frequency ignition of the arc is useful as it ensures that thin seams are made as accurately as possible.

Finally, each semi-automatic inverter has three main functions that simplify MMA welding and ensure high-quality results:

  • Hot start – facilitates the ignition of the arc;
  • Arc afterburner – stabilizes the arc in difficult manual welding conditions;
  • Anti-sticking – makes it easier to remove the electrode if it sticks to the metal surface.

Conclusion

MIG/MAG technology is often referred to as “continuous electrode welding”. In fact, what could be better when both the material and the working tool are “continuous” wires that are fed automatically? The welder does not have to feed filler material or change the electrode in the torch regularly. Only the required operating parameters need to be set. When selecting a semi-automatic machine, first consider your application and the corresponding technical features of the machine. Then, check the selected models for the functions you require. If you have no experience with welding, you should check the automatic setting options of the inverter.

Author

  • Eddie Jones

    Eddie Jones was brought up in Allentown, Pennsylvania. He is a proud Managing content editor, he got a taste of Tig welding from a steel town, on the Lehigh River, in his high school shop class. He holds certificates for Certified Welding Educator (CWE) and Certified Resistance Welding Technician (CRWT) from the American Welding Institute. He is interested in scuba diving, sculpture, and kayaking

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