Welding

 

Manual metal arc welding - (MMA)

Manual metal arc welding (MMA) or stick welding is a process that melts and joins metals by heating them using a metal arc between the coated metal electrode and the workpiece. The outer coating of the electrode helps with the making of the arc and provides protective gas and a wrap of slag (dross) to protect the weld against contamination. The core of the electrode provides the largest part of the metal that fills the weld.

When the electrode moves along the workpiece with proper speed, metal deposits in uniform layer are called - seam.

Power source of the arc (stick) welding provides a constant current (CC) and can be an alternating current (AC) or direct current (DC), depending on the electrode being used. Best results of the welding are usually obtained using a DC power source.

Strength in the welding wheel is measured with voltage and current. Voltage (Volt - V) is determined by the length of arc between the electrode and the workpiece, and is conditioned by the diameter of the electrode. Electricity is a convenient measure of the strength in welding and is measured with amperes (A).

Amperage necessary for the welding depends on the diameter of the electrodes, the size and thickness of the pieces to be welded and the welding positions. Basically, lower electrode and lower amperage are needed for welding smaller pieces than for a larger piece of the same thickness. Thin metals require less electricity than thick metals, and a small electrode requires lower amperage than large electrode.

It is better to weld the workpiece in portrait or horizontal position. However, when you are forced to weld vertically or overhead, it is useful to reduce the amperage than the one used in the horizontal position. The best results of the welding are achieved by maintaining a short arc, moving the electrode with single speed and moving the electrode to the weld metal, with constant speed as it melts.

Power supply of NV-xxx series is a DC welding rod or arc welding machine. On the front panel of the welding power source, there is the power source indicator (white), the overheating or over-current indicator (yellow), button or a controller for adjusting the welding current, the positive output voltage (+), the negative output voltage (-). On the rear panel of the power source for welding, there is an ON / OFF switch mode of power supply, the power supply cable (connected to 1 ̴, 50/60 Hz, 220 / 230V AC) etc.

Positive linkage means that the workpiece is connected to the output (+) welding power source and electrode holder or a torch (torch welding gun) is connected to the output (-). Negative linkage means that the workpiece is connected to the output (-) of the welding power source and electrode holder or torch (torch welding gun) is attached to (+).

Selection of a positive or negative connection depends on the type of the electrode. When welding electrode for an acid, for example E4303 and E6013, you use positive or negative linkage. For welding the basic electrode – ex. E 5015 you use mainly negative linkage.

Connect the workpiece or the electrode holder to the output (-), not loosely.

Connect the electrode holder or workpiece on the output (+), not loosely.

Turn ON / OFF power switch, power supply indicator (white) - bright.

MMA welding process will run.

In order to improve the quality of welding, pliers for the mass on the workpiece should be clamped firmly and as close as possible to the place of welding.