Comparison GH Multi-MIG-300 Profi vs Apro MIG-300

Among the main types of welding can be called manual arc (MMA), semi-automatic (MIG / MAG), argon-arc (TIG), spot (SPOT), spot (STUD) and plasma cutting (PLASMA) welding.

— MMA. Welding using an electric arc and a consumable electrode with a special coating. The electrode is fed and moved manually by the welder. Shielding gas supply is not provided; protection of the weld pool from air can be carried out due to the combustion of the coating deposited on the electrode. This welding technology allows the use of the simplest equipment, it is undemanding to the quality of the current and the design of the welding machine. On the other hand, the quality of the resulting weld is highly dependent on the skills of the welder, the productivity of the process is relatively low, and this technology is poorly suited for non-ferrous metals — its main purpose is the welding of steel and cast iron.

— MIG/MAG. Partially automated welding in an inert (MIG) or active (MAG) gas environment. The gas enters directly to the place of welding through the burner and, when the arc burns, forms a protective sheath that covers the weld pool from exposure to air. And the term "semi-automatic" means that filler material in the form of a thin wire is also automatically supplied to t...he place of work (but you need to move the burner manually). The choice between inert and active gas is made depending on the materials being welded — for example, the first option is usually used with non-ferrous metals, the second with steel. Such welding provides a much better quality of the seam than manual welding, and also increases the convenience and speed of work — in particular.

— TIG. Manual welding with a non-consumable electrode in an inert gas environment. With such welding, the electric arc melts only the edges of the parts to be joined, and the final seam is formed from them, without using the electrode material (in some cases, additives in the form of pieces of metal of the appropriate shape can be used). To protect the seam from exposure to air, a protective gas, usually argon, is supplied to the heating point. TIG welding is well suited for stainless steel as well as copper and aluminium alloys. It allows you to create a more accurate seam than the same MMA, and more precisely control the process. On the other hand, this technology is quite demanding on the skills of the welder, and the speed of work is relatively low.

— SPOT. Electric welding, carried out due to the point impact of high currents. It is used for connecting thin sheets of metal (mainly up to 3 mm), as well as for attaching pins and studs to a flat base. When connecting sheets of metal, two electrodes with a relatively small diameter tightly press the workpieces against one another, after which a current is passed through them with a force of the order of several kiloamperes; the metal at the point of contact is heated to the melting point, which ensures the connection. When attaching pins and studs, the role of one of the electrodes is played by the pin itself, the role of the second is played by a flat base. SPOT type welding is very popular in car manufacturing and car service: it is in this way that some elements of car bodies are connected, and it can also be useful for straightening. There are unilateral and bilateral. The first uses a single electrode, which is pressed against the workpiece with force. The main advantage of this option is the ability to work with surfaces that are accessible only from one side — for example, car doors. Actually, one of the main areas of application for one-sided SPOT welding is a car service, in particular, straightening car bodies and other car surfaces. The second welding (two-sided) involves the use of a pair of electrodes that compress the junction from both sides, like a vice. This variant is better suited for work with thick parts or where a high reliability of the connection is required — due to the compression described, it is easier to achieve the desired depth of the weld pool. On the other hand, its use requires access to both sides of the workpiece. Note that some models of welding machines are able to work according to one and the other scheme; this makes the device very versatile, but may come at a cost.

— STUD. Spot welding technology using a lifting (pulling) arc. Mainly used for flat base plus stud connections. The welding process itself takes place in the following way: the stud is pressed against the base; the current is switched on; the pin rises; an arc ignites between it and the base, which melts the surface of the base; the hairpin is lowered into the melt; the current is turned off, the metal freezes. STUD welding involves the use of mechanized welding torches with a spring or hydraulic system that raises and lowers the stud, and an inert gas or flux is used to protect the joint from atmospheric air.

– PLASMA. Cutting metal using a stream of heated plasma — a highly ionized gas. To do this, gas (inert or active) is supplied to the place of work, which, due to the influence of an electric arc, is ionized, heated and accelerated. The plasma temperature can exceed 10,000 °C, and the speed is 1,000 m/s, which makes it possible to work with almost any metals and alloys, including refractory ones. At the same time, cutting is carried out quickly, the cut is clean and neat, and the cutting depth can reach 200 mm. The main disadvantage of plasma cutting is the high cost of equipment.

The minimum actual input voltage at which the welding machine remains operational.

Such information is useful primarily for working in unstable networks, where the voltage tends to “sag” a lot, as well as from autonomous power sources (for example, generators), which can also produce voltage below the nominal one.

The maximum power consumed by the welding machine during operation, expressed in kilowatts (kW), that is, thousands of watts. In addition, the designation in kilovolt-amperes (kVA) can be used, see below for it.

The higher the power consumption, the more powerful the current the device is capable of delivering and the better it is suitable for working with thick parts. For different materials of different thicknesses, there are recommendations for current strength, they can be clarified in specialized sources. Knowing these recommendations and the open circuit voltage (see below) for the selected type of welding, it is possible to calculate the minimum required power of the welding machine using special formulas. It is also worth considering that high power creates corresponding loads on the wiring and may require connection directly to the shield.

As for the difference between watts and volt-amperes, the physical meaning of both units is the same — current times voltage. However, they represent different parameters. In volt-amperes, the total power consumption is indicated — both active (going to do work and heat individual parts) and reactive (going to losses in coils and capacitors). This value is more convenient to use to calculate the load on the power grid. In watts, only active power is recorded; according to these numbers, it is convenient to calculate the practical capabilities of the welding machine.

Power consumption of the welding machine, expressed in kilovolt-amperes.

kVA is a unit of power used in welding machines along with the more traditional kilowatts. The physical meaning of both units is the same — current multiplied by voltage; however, they denote different parameters. So, in kilowatts, only a part of the total power consumption is recorded — active power (goes to do work and to losses due to heating of individual parts); according to this indicator it is convenient to calculate the practical capabilities of the device. And kilovolt-amperes denote the total energy consumption — it also takes into account reactive power (it goes to losses in coils and capacitors during the operation of alternating current circuits). This data is useful for calculating the total load on the network or other power source.

The apparent power input in kVA will always be greater than the power in kW. However, some manufacturers go to the trick and indicate full power not at full, but at partial (for example, half) load. This gives the impression of efficiency, but is incorrect from a technical point of view. As for the ratio of energy consumption, the active power in kW is often 20-30% lower than the apparent power in kVA. So, in terms of kilovolt-amperes, it is quite possible to evaluate the performance of the unit.

As for specific values, in the most modest models they do not exceed 3 kVA. An indicator up to 5 kVA is considered low, up to 7 kVA — average, and in the most powerful units, the power consumption can reach 10 kVA or even more.

The voltage supplied by the welding machine to the electrodes. As the name suggests, it is measured without load — i.e. when the electrodes are disconnected and no current flows between them. This is due to the fact that at a high current strength characteristic of electric welding, the actual voltage on the electrodes drops sharply, and this does not make it possible to adequately assess the characteristics of the welding machine.

Depending on the characteristics of the machine (see "Type") and the type of work (see "Type of welding"), different open circuit voltages are used. For example, for welding transformers, this parameter is about 45 – 55 V (although there are higher voltage models), for inverters it can reach 90 V, and for semi-automatic MIG / MAG welding, voltages above 40 V are usually not required. Also, the optimal values \u200b\u200bdepend on type of electrodes used. You can find more detailed information in special sources; here we note that the higher the open-circuit voltage, the easier it is usually to strike the arc and the more stable the discharge itself.

Also note that for devices with the VRD function (see "Advanced"), this parameter indicates the standard voltage, without reduction through VRD.

The smallest current that the device is able to supply through the electrodes during operation. For different materials, different thicknesses of the parts to be welded and different types of welding itself, the optimal welding current will be different; there are special tables that allow you to determine this value. The general rule is that a high current is far from always useful: it gives a rougher seam; when working with thin materials, it is possible to melt through the junction instead of connecting the parts, not to mention excessive energy consumption. Therefore, if you have to work with parts of small thickness (2-3 mm), before choosing a welding machine, it makes sense to make sure that it is capable of delivering the desired current without “busting”.

The highest welding current at which the machine is able to operate with a duty cycle of 100%.

See below for more information on the frequency of inclusion (PV). Here we recall that “100% duty cycle” means continuous operation, without shutdowns for cooling. Thus, the maximum welding current at 100% duty cycle is the highest current at which the machine can be used without interruption. Usually, this current is much lower than the maximum.

The duty cycle allowed for the welding machine.

Almost all modern welding machines require breaks in operation — for cooling and general "recovery". The frequency of inclusion indicates what percentage of the time of the total work cycle can be used directly for work. In this case, 10 minutes is usually taken as a standard cycle. Thus, for example, a device with a duty cycle of 30% will be able to work continuously for less than 3 minutes, after which it will need at least 7 minutes of interruption. However, for some models, a cycle of 5 minutes is used; these nuances should be clarified according to the instructions.

In general, high frequency is required mainly for high-volume professional work; with a relatively simple application, this parameter does not play a decisive role, especially since you have to take breaks during work. As for specific values, the mentioned 30% is a very limited figure, typical mainly for entry-level devices. A value of 30 – 50% is also low; in the range of 50 – 70% is the majority of modern devices, and the most "hardy" models provide a frequency of more than 70%.

The largest diameter of the electrode that can be installed in the welding machine. Depending on the thickness of the parts, the material from which they are made, the type of welding (see above), etc. the optimal electrode diameter will be different; there are special tables that allow you to determine this value. Large diameter may be required for thick materials. Accordingly, before purchasing, you should make sure that the selected model will be able to work with all the necessary electrode diameters.

In modern welding machines, an electrode diameter of 1 mm or less is considered very small, 2 mm — small, 3 mm and 4 mm — medium, and powerful performant models use electrodes of 5 mm or more.