Semiautomatic welding machine: choice, consumables and subtleties of use

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Welding with a wire in a shielded gas environment is positioned as a tool for amateur craftsmen, however, the technology of work has its own subtleties. First of all, you need to understand the specifics of the semiautomatic welding machine, be able to choose consumables and maintain equipment in accordance with technical regulations..

Features of MIG-MAG machines

The essence of the work of a semi-automatic welding machine is the mechanized feeding of a filler wire, which is under the potential of a constant pulsating current. To ionize and maintain the arc, a shielding gas is injected into the welding zone, which is usually carbon dioxide or a mixture of CO2 and argon. The main advantage of MIG-MAG is the absolute freedom of welding in any spatial positions of the seam without changing the settings and using special working methods.

Semiautomatic welding machine: choice, consumables and subtleties of use

Structurally, the welding machine includes an inverter converter, arranged according to the same principle as in power blocks for welding with coated electrodes. However, there are two specific components: the gas valve and the automatic wire feeder. Both of them are activated at the same time as the voltage is applied to the wire, however the speed and the order of switching can be adjusted individually.

Wire pulling can be carried out by two or four rollers, of which only half serve as drive rollers, the rest – as pressure rollers. A high-quality device has a feed speed switch, and the most advanced ones have a separate vernier for adjusting it. In this case, the wire feed speed is additionally adjusted by the control unit depending on the value of the welding current.

Semiautomatic welding machine: choice, consumables and subtleties of use

The gas valve is designed to supply shielding gas to the welding area before energizing. Unlike more advanced non-consumable electrode equipment, semi-automatic welding machines do not provide the ability to adjust the gas supply modes. Therefore, it is important that the control unit itself provides for a slight advance in turning on the valve when the start button is pressed in order to expel air from the burner and hose. Flushing is not required at the end of welding with a semiautomatic device. To adjust the gas flow rate, use special balloon reducers with a flow meter.

Separately, it is necessary to touch upon the issue of the choice of power. In the amateur segment, the maximum operating current of the device is limited to 160–180 A, which is absolutely enough for training and working with wires up to 0.8 mm. The limiting current in this case is 120-130 A, however, with a certain skill, a 0.8 mm wire can be welded at currents up to 160 A, achieving a penetration depth of 4.5-5 mm. With a further increase in the current strength, the penetration depth does not increase; this requires the use of a larger diameter of the filler material. Accordingly, the limiting current of the apparatus should be at least 180-200 A for a wire of 1 mm, from 240 mm for a wire of 1.2 mm, and so on with a gradation of 30-40 A.

Burner and hose selection

The variety of MIG-MAG torches is much higher than that of welding machines, which is explained by both individual needs for ergonomics and all kinds of technological design features, due to which a number of specific tasks for metal welding are solved. And yet, choosing the right burner for a novice user is quite simple, it is only important to take into account a few circumstances..

Semiautomatic welding machine: choice, consumables and subtleties of use

To begin with, you should weed out all the options that do not have a unified European connector: burners of this particular type are much more common, and therefore are interchangeable both in assembly and in terms of consumables. For example, the diameter and pitch of the current collector lugs in them are practically the same, the same applies to the nozzle tip with its locking system..

Sleeve length is usually 3 meters, less often 4-meter modifications come across. It makes no sense to buy a torch with a 5 meter sleeve: to pull a wire of this length requires an improved feeder with two drive rollers, and it does not always cope. However, modern inverter technology is lightweight, and therefore a possible lack of sleeve length is easily compensated for by a longer gas hose and power cord..

Semiautomatic welding machine: choice, consumables and subtleties of useEuro connector for Mig Mag semiautomatic device

Special attention should be paid to the type of wire channel. For steel additives, a spiral-wound metal channel is installed inside the sleeve, but in the case of using aluminum wire, a Teflon channel is required to exclude increased friction of the soft metal against the walls. The inner diameter of the channel should be selected in accordance with the thickness of the wire used, as a rule, there are three gradations of this parameter, marked with the color of the outer sheath.

For the possibility of welding in reverse polarity, when the flow of electrons is directed from the part to the nozzle and heats it up strongly, it is recommended to choose a torch with an increased neck length to reduce the degree of heating and additional radiator neck ribbing. The issue of overheating is effectively solved in water-cooled torches, but this is not the best choice for a novice welder, because in addition to the pumping station, it also requires the use of a welding machine with an increased on-time up to 100%.

Semiautomatic welding machine: choice, consumables and subtleties of use

The permissible operating current of the burner must be 20–25% higher than the capabilities of the device. Of the additional useful options, we can note the presence of a valve in the handle, the presence of which eliminates the need to blow the hose every time after a long break in work. Also, burners with articulated-rotary sleeve entry are recommended very well, they are more durable.

Adjustment and maintenance of the nozzle and torch

The duty of every welder is to monitor the condition of the nozzle and service it in time. This mainly concerns the tip, through which the welding current is transferred to the wire. Its diameter is selected in accordance with the thickness of the filler material, while the tolerance for the gap in the hole is strictly regulated.

Semiautomatic welding machine: choice, consumables and subtleties of use

Over time, due to friction, the hole in the tip enlarges, which leads to a deterioration in the current collection. This is reflected in the deterioration of the stability of the arc burning and the appearance of a characteristic crackle during welding. On average, replacement of the nozzle is required regularly as the wire is consumed; this element should be replaced after 2–2.5 kg of filler material has been used up. During the replacement process, a special wrench from the delivery set is used, with which the old tip is unscrewed, and the new one is screwed into place, while the tightening force should not be excessive, so as not to unscrew the gas atomizer having a left-hand thread.

Separately, you need to monitor the condition of the broaching channel. The copper coating gradually crumbles as it passes through the broaching mechanism and the channel, which may cause the wire to jam in the channel. To prevent this from happening, after every 5 kg of wire has been worked out, the hose must be blown with compressed air.

Semiautomatic welding machine: choice, consumables and subtleties of use

In addition to the standard copper-plated wire with a diameter of 0.8 mm to 1.6 mm (with a pitch of 0.2 mm), there is also a special flux-cored wire. When using it, the presence of a shielding gas in the welding zone is not required, however, it is a more expensive type of additive. As a rule, welders keep a small amount of such wire in stock in case of an unexpected carbon dioxide depletion or for field work. Flux cored wire is more expensive and is not designed for continuous use due to the more intense sparks generated during welding, which does not add to the durability of the nozzle and tip. In general, a non-stick spray can be recommended to avoid metal spatter sticking to the inside of the nozzle..

First start-up and maintenance

Before giving the first spark to a new device, it is necessary to carry out its initial maintenance. The first step is to remove any residual preservative grease from the rollers of the pressure mechanism, for which aerosol brake disc cleaners are well suited. Afterwards, the rollers should be kept clean and dry by periodically cleaning them each time the collector tip is replaced. With the next blowing of the sleeve, it will not be superfluous to clean the channel of the drive roller: by pressing the forced wire feed button, remove the copper dust from the groove with an awl, and then slightly sand the surface with a zero sandpaper.

Semiautomatic welding machine: choice, consumables and subtleties of use

Before the first start, it is necessary to adjust the brake force by turning the axle screw. The hub should be relatively easy to rotate by hand with no inertial run-out. That is, when the wire spool is turned sharply, it should stop exactly in the position at which the turning force was stopped. The braking mechanism should not be lubricated; it is enough to apply only a small amount of non-stick spray to the area of ​​the clamping screw once or twice a year.

After installing the cassette with the additive and fixing it with a wing nut, the edge of the wire is carefully removed from the locking hole in the coil wall and fits into the groove of the drive roller, and then is inserted into the hole of the connector. In this case, the wire must not be released from the hands, otherwise it will instantly unwind. When the end of the wire protrudes 20-30 mm from the connector, the pressure roller is lowered. It is usually equipped with an adjustable pressure device, the flywheel of which, in normal operation, should be between 2 and 3..

Semiautomatic welding machine: choice, consumables and subtleties of use

When the clamping mechanism is adjusted, the protruding edge of the wire is carefully inserted into the sleeve channel and the connector is installed in place. Please note that when replacing the wire until the coil is completely consumed, it is usually cut off with wire cutters, which results in a flattened edge. To prevent the wire from getting stuck during the next broach, the burrs must be carefully removed with a file.

After preparing the welding machine, it is necessary to connect gas equipment to it. For these purposes, a reinforced hose is optimal, which is put on one end of the reducer fitting, and the other is attached to the standard device inlet, where it is crimped with a screw clamp. When the gas is connected, it is necessary to unscrew the valve on the cylinder, set the outlet pressure according to the welding equipment passport and adjust the flow rate. Now you can carry out the first test of the semiautomatic device.

Welding modes

Typically, MIG-MAG welding machines have two verniers for adjusting the voltage and welding current. It is also possible to have an inductance regulator, which makes it possible to achieve more precise adjustment of welding modes. It should be noted that the absence of such a regulator does not indicate an imperfection of the apparatus: it is quite possible that the adjustment of the inductance of the welding current is carried out by the controller automatically.

Semiautomatic welding machine: choice, consumables and subtleties of use

Set the actual value of the welding current should be in strict accordance with the parameters indicated on the packaging of the wire. The voltage and inductance regulators must initially be given a middle position and the machine must be tested in operation. If a crackling sound is heard during welding, the arc is unstable, or metal vaporization is observed, this is eliminated by adjusting the applied voltage, which generally determines the melting point. Depending on the thickness and type of metals to be welded, different applied voltage may be required, therefore, before welding the next structure with a semiautomatic device, several test seams are usually performed.

The inductance setting helps to adjust the penetration depth and weld pool width. At minimum values, a narrow seam with a high peaked bead will form. If you give the maximum value, the bead will be flatter, and the penetration depth will approach the maximum value for this type of wire..

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