Systems of automatic control of arc welding

The systems for automatic control of arc welding can be divided into several main groups. The first group covers the systems, which use the arc self-regulation phenomenon. The most representative of such systems is a device for mechanized consumable-electrode welding, which consists of a welding diode rectifier and a drive with a stabilized wire feed rate. The advantages of such systems are their comparatively low cost, their ease of operation and their reliability. The self-regulation process does not eliminate the influence of a large number of disturbances which include the variation of the mains voltage, deviations of the electrode stick-out, irregular transfer of the electrode metal, electrode displacement relative to the butt, part assembly defects and many others, which lead to a higher probability of defects.

The influence of the disturbances can be alleviated by using the automatic control systems of the second group, in which the final control elements are the arc power source and wire feed drive. Such systems can completely neutralize the influence of the mains voltage variation and significantly alleviate the consequences of the welder’s hand movements. Control of the power source or the wire feed rate permits the ‘single-button’ systems to be developed. These maintain the optimum welding parameters, depending on the wire feed rate set by the welder or the arc voltage.

The second group also includes systems for control of the welded pint shape, namely, the penetration depth, weld width and deposited-bead height. Besides current, voltage and speed of welding, magnetic stirring of the pool metal and transverse oscillations of the electrode with a certain amplitude and frequency can be also used as control actions. Control of the transverse oscillations of the electrode and welding speed, which is carried out through the groove width feedback, allows the deviations in the dimensions of the groove and the parts assembly to be compensated for to a certain extent.

The third group includes systems for control of the electrode metal melting and its transfer into the weld pool. These systems enable fast control of current, wire melting rate, drop dimensions and its transition into the weld pool. These systems eliminate the irregular disturbances of the weld pool by large drops and simplify the technique of making the weld in various positions in space.

The forth group of systems covers systems of automatic guidance to the weld line. Such systems are becoming increasingly popular owing to the expanding application of robots for arc welding.

Exercises

1. Learn the following words and word-combinations:

diode rectifier -діодний випрямляч;

disturbance -порушення;

deviation -відхилення;

penetration depth -глибина проникнення;

weld width -ширина зварювання;

deposited bead height -висота шву;

magnetic stirring -магнітні коливання;

groove -паз

Дата добавления: 2015-11-16