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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Electric welding semiautomatic device. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / welding equipment I am sure that a compact electric welding semiautomatic device (ESPA), the flawless operation of which is guaranteed by electronics and a protective environment of carbon dioxide, will not be superfluous in any household. Especially when repairing the lining of agricultural machines or car bodies, as well as when making permanent joints from a thin (for example, aluminum or steel) sheet, when, in order to avoid burn-through, the metal heating area should be minimal, but not to the detriment of the quality of the seam. It is this ESPA that I recommend making in a home workshop or in a garage, from widely available assemblies, parts and materials, with a minimum of turning and complex plumbing operations. Well, if there are difficulties associated with electrical and radio engineering, then there is always the opportunity to turn to experienced radio amateurs (say, from among relatives, friends, neighbors or just acquaintances and responsive specialists) who will help to correctly assemble and debug the electronic part of the semi-automatic welding machine . Take, for example, the power supply of the arc, which includes a welding transformer T1, with a diode bridge VD1-VD4 and a choke L1, as well as a thyristor voltage regulator. The voltage on the primary winding T1, and hence on the arc itself, is set using resistor R5. The latter forms, together with C1 and C2, phase-shifting chains, from which control signals for thyristors VS1 and VS2 come.
The peculiarity of the circuit solution used here is such that each of the thyristors is operational only if there is a corresponding half-cycle of the anode mains voltage. Moreover, these controlled semiconductor devices are opened for a time controlled by the electrical parameters of the phase-shifting chains. Welding transformer T1 is no different from its prototypes. In fact, this is a well-known converter of the mains 220-volt AC voltage to a reduced, 56-volt one, made on the stator from a burned-out electric motor. The cross section of the toroidal magnetic circuit, which is formed after the removal of the slot jumpers at the workpiece, is 40 cm2 in the author's version. As practice shows, the primary winding of a welding transformer for ESPA should contain 220 turns of copper wire with a diameter of 1,9 mm, preferably in fiberglass insulation. Well, in the secondary it is enough to have, respectively, 56 turns of a multi-core cable or bus with a cross section (for copper!) 60 mm2. The rectifier bridge diodes are designed for a direct current of at least 100 A. For better cooling, each of them is equipped with a radiator with a heat transfer area of 200 cm2. Very good, for example, is a bridge consisting of two groups of powerful bipolar valves V200 and VL200, the design of which ("anodic" or, conversely, "cathode" heat removal and, accordingly, green or crimson housings) makes it easy to combine them into a compact rectifier block with "plus" and "minus" halves of the bridge. Homogeneous groups are fastened with M8 studs, and a rubber gasket with two symmetrical sections of radiators is installed between heterogeneous groups. Detailed material on such a technical solution was published in the magazine "Modelist-constructor" No. 5 for 1997. Choke L1 is used for reliable ignition of the arc. In this case, the core from the power transformer of the 3rd generation TV ("Temp-738") or a similar one with a cross section of 15-20 cm2 serves as a magnetic circuit. The base "silovik" is disassembled, all windings are removed from it. Between the halves of the core blank, plates of textolite 2 mm thick are placed. The magnetic circuit obtained with a gap is wrapped with two layers of a keeper tape, on top of which a winding is placed, consisting of 30 turns of an insulated copper core or a wire bundle with a cross section of 20 mm2. The power supply unit of the electric motor M1 of the feeder and the pneumatic valve K2 is assembled according to the scheme of a parametric stabilizer. Transformer T2 lowers the mains voltage to 15 V, which, after rectification by the diode bridge VD5-VD8, is smoothed by capacitor C3 and fed to VT2, which serves as a regulatory element. With the help of resistor R7, the output voltage of the stabilizer is set, and hence the speed of rotation of the motor M1. When the button SB2 is pressed, relay K1 is activated. It, in turn, closes the power supply circuit of the electric motor and the pneumatic valve, and the VD13 diode protects the K1.1 contacts from burning. As K1, the high beam headlight relay is used. Pneumatic valve K2 from the EPHH system of the VAZ-2107 car. In the role of T2, any, including a home-made, step-down transformer with a voltage in the secondary winding of 15-20 V and a current of 10 A is acceptable. Capacitors and resistors are common, indicated on the rating diagram. The only exception can be R6, the resistance of which is found according to Ohm's law, where the voltage U \u3d Uc18 - 0,01 (V), and the current I \uXNUMXd XNUMX (A). The welding torch is used to supply the "electrode" wire, arc voltage and carbon dioxide to the welding site. The channel for the welding wire is made from a sheath of a 1,2 mm speedometer drive cable. A guide tube with M4 external thread at the end is soldered into one of its ends, and the other is soldered into the burner channel.
The SB2 button is mounted on a U-shaped bracket, which is soldered with copper to the burner channel. Using copper solder, a 20 mm2 power cable, not shown in the figure, is connected (or even screwed) coming from the L1 choke. A copper tube is also soldered with a hose for supplying carbon dioxide put on it. The textolite body of the burner has a collapsible design not shown in the figure. All hoses and cables are assembled into bundles and fastened in place with four to five lightweight bandages.
For the feed mechanism, an engine with a gearbox from the drive of the GAZ-69 wiper was used. The output shaft of the reducer is shortened to 25 mm and the M5 left thread is cut at the end, which is necessary for self-tightening of the drive roller when feeding the wire. The driven roller freely rotates on an axis with a diameter of 5 mm, passing through the slats and the frame formed by the clip and the slat, firmly tightened with a nut. On the front side of both rollers, teeth are cut at a width of 5 mm, which engage with each other during the operation of the mechanism. The number and module of teeth can be any (in this case, z = 15; m = 2 mm). And on the back side, both are knurled at a width of 10 mm for better engagement of the welding wire. Of course, such rollers after their manufacture must be hardened. The frame of the driven roller is mounted at one end on an axis passing through the bracket and bushing, and tightened with a nut. The thickness of the bushing is selected when adjusting the mechanism so that the teeth on both rollers match. At the other end of the frame, a spring is tensioned, with the help of which the welding wire is clamped between the rollers. The height of the brackets for the guides of the welding wire is selected so that it runs in the middle of the knurled surface of the rollers. The feeder, pneumatic valve, switch SB1, resistors R5 and R7 are fixed on a 6 mm thick textolite plate, which is the lid of the box that houses the electronic part of the ESPA. Ventilation holes are drilled on the side walls and in the bottom of the box. The coil with welding wire is fixed with a clamp on the capstan from the player. The capstan is placed at a distance of 200 mm from the feeder so that with half the rest of the wire, it is on the same axis with the guides during operation. Before work, the guides must be brought as close as possible to the rollers and tightened with nuts. Then pass the welding wire through the guides, mechanism, torch and tip. The tip must be screwed into the burner channel and put on a protective cover, which must be tightened with a screw. Having connected the hose from the carbon dioxide cylinder with a reducer to the pneumatic valve, it is required to set the gas pressure to about 1,5 atm using the reducer. After turning on the power, it remains only to adjust the wire feed speed with the resistor R7 (and with the help of R5 - the required voltage) and start welding. ESPA can work with wire with a diameter of 0,8-1,2 mm, you only need to change the diameter of the tip hole and adjust the voltage on the arc. Welding is best done with a "back angle" (meaning the angle between the seam and the torch), which results in a stable arc and a quality seam. However, features should also be taken into account. When welding lap joints, it is desirable to direct the burner at an angle of 55-60° to the plane of the sheets, and when welding T-joints with a vertical wall, at an angle of 45-50° to the bottom wall. Wire stick-out (distance from the weld plane to the tip) during welding should be set in the range of 5-15 mm for wire with a diameter of 0,5-0,8 mm and 8-18 mm when the welding wire is thicker. Reducing the overhang threatens to quickly foul the torch with metal splashes and complicate the observation of the welding process. At the same time, in this mode of operation, the arc is better excited and its stability increases. It is necessary to work with ESPA in a welder's suit, having protective gloves on your hands, and on your face - a mask with a light filter corresponding to the welding current. Moreover, if Iw is 15-30 A, you should use a C3 light filter, C4 is preferably used at 30-60 A. With a higher welding current, C5 can be recommended. and even super-compacted light filters (C6 or C7), given that the maximum value of Ib for ESPA is about 120 A. It is also necessary to remember the strict observance of the rules of electrical and fire safety. Author: M. Kostin, Penza
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