Welding semiautomatic device in carbon dioxide gas environment with automatic feeding of welding wire. Encyclopedia of radio electronics and electrical engineering

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To the attention of those who like to "repair" vehicles with their own hands, the author's scheme and design are offered for self-assembly welding semi-automatic in a carbon dioxide gas environment with automatic feeding of the welding wire into the welding zone.

Purpose and description of the device

Motorists know that for welding the body of "iron" horses, only an AC arc electrode welding machine is not enough - the thin metal of the body requires accurate and preferably fast spot welding. Of course, there are several types of welding machines of various kinds available to private car owners, for example, oxy-acetylene welding or carbon dioxide welding.

But compared to oxy-acetylene welding, semi-automatic welding in carbon dioxide has significant advantages:

- the heat-affected zone is very narrow, so the part is deformed very little or not at all;

- the paint on the part burns out in a thin strip, which reduces the amount of preparation, straightening and coloring of the product;

- because the rate of melting of the electrode wire is very high - the overall productivity of welding is 2-3 times higher;

- the quality of the weld is better;

- very precise fitting of parts before welding is not required;

- a high-quality seam is obtained even with different thicknesses of the parts to be welded;

- carbon dioxide is less deficient than oxygen or acetylene;

- the way of welding is mastered easily and quickly.

For semi-automatic welding in a carbon dioxide environment, the domestic industry produces various equipment: A-537, A-537U, A-547R, A-825M, A-1230M, etc., so organizations may be more interested in these finished industrial devices, and amateurs , who held a soldering iron in their hands, the author suggests that they themselves assemble a similar simple apparatus developed by him, which he has been operating for the 3rd year.

On the one hand, carbon dioxide protects the molten metal from the effects of oxygen and nitrogen in the air, on the other hand, it decomposes into carbon monoxide (carbon monoxide) and oxygen, which oxidizes the metal. To compensate for oxidation, a special copper-plated electrode wire containing silicon and manganese is used: Sv-08GS, Sv-08G2S, Sv-10GS, Sv-12GS, as you can guess from the designations - 0.8, 0.8, 1.0 and 1.2 mm in diameter, respectively. Practical numerical data, which must be kept fairly accurately (especially for tensions.) in order to avoid poor welding quality, are given in Table 1.

Welding modes in carbon dioxide 

Table 1

The author in his design used 0.8 mm copper-plated electrode wire, which he managed to buy on the market. Therefore, the circuit is designed specifically for the operating mode corresponding to the first line of Table. 1.

Device layout

Shown in fig. one.

(click to enlarge)

Its basis is a powerful welding transformer T1, which is connected to a 220 V network by a switch on anti-parallel optothyristors VS1, VS2, controlled by a key VT1-VT2 and Provides:

- welding voltage from the output winding II (according to the first line of tab. 1), rectified by the bridge VD1 ... VD5, smoothed by the filter L1-C1 (R3 ballast resistor, discharges C1 at idle);

- supply voltage (from the output winding III) of the electric motor supplying the welding wire, which is turned on by the VT8 key through the voltage regulator C6-DA2-R11-R12-C7 and the output powerful transistor VT7;

- supply voltage (from the output winding III, reduced to 12 V by resistor R9) of the KL1 gas valve, which is turned on by the VT5-VT6 electronic key.

With the switch SA2 of the primary winding, you can change the output voltage from about 18 ... 21 V.

The device is turned on by pressing the SA1 "Start" button, which is connected to the input of the cascade to VT3 (with an R4C2 circuit at the input), which is an anti-bounce key with two wires from the button (if you wish, you can apply standard anti-bounce solutions to trigger ICs , logical elements, but they require three wires from the button, and only two wires for the button are laid inside the standard industrial "holder" of the semi-automatic welding machine used by the author).

A silicon diode VD4 is connected to a similar key on VT14, which can be fixed as a temperature sensor on the hottest node of the circuit during its long operation, select a suitable temperature threshold with resistor R4, at which VT4 will close and through DD1.4 turn off all nodes of the device. But if your design does not overheat anywhere during prolonged operation, then the entire VD14-R4-R6-C3-VT4-R7-DD1.4 node can be removed from the circuit

The necessary phases of the control signals for the output nodes of the device (T1, gas electrovalve KL1, electric motor) are provided by only one IC DD1 155LA3, which, together with VT1, VT2, VS1, VS2, VT3, VT4, is powered by a stabilized DD1 voltage of 5V from a low-voltage rectifier T2- VD9…VD13.

Rectifier Diodes

VD1-VD5 - powerful, for the corresponding welding current, they can be of the following types: D151-160 (maximum direct current 160 A), D161-200 (maximum direct current 200 A), V200-6 (maximum direct current 200 A), B2-200-9 (maximum forward current 200 A). The rest of the radioelements, I think, do not present any difficulties in choosing or replacing.

Design

Welding T1 should have a power of about 2.5-3 kW. The author calculated it based on the available winding material, i.e. a copper bus with a cross section of 6 x 8 mm for the secondary winding II T1 and a rod (O-shaped) magnetic circuit (core cross-sectional area 42 sq. cm, core "window" area 200 sq. cm) for a voltage of 21 V and a current of 120 A.

Both windings are wound symmetrically, i.e. on a rod (O-shaped) core half of the winding on each side. And do not forget to correctly connect the halves to each other, in phase (the end of one with the beginning of the other), otherwise you will get a 3 kilowatt electric heater ;-). And then not for long: the winding or wiring without a fuse will burn. If you use SA2 in your circuit, then make taps 1 turn from the edge of the winding.

Primary winding

The low voltage transformer T2 is calculated similarly for an output voltage of 6V and a load current of 1A.

Choke L1 is wound with a thick welding cable on the stator of some engine with a slot, i.e. its inductance turned out to be arbitrary, of the order of 10 ... 20 μH. Capacitor C1 has a capacity of 4000 microfarads, but you can put more. The quality of the arc, and hence the welding seam, depends on the stability of the voltage.

As an engine, the author used a 24 V windshield wiper engine from KamAZ. It consumes a current of about 3 A.

The gas valve - again from the car - a 12-volt valve for supplying water to the wiper from the "eight" (VAZ 2108). Consumption - about 0.4 A.

"Derzhak" welder - industrial production for semi-automatic welding (unfortunately I don't know the type): a rubber hollow hose ~ 3 cm in diameter, inside there is a steel twisted "shirt" for welding wire and two insulated wires for the "Start" button. The hose delivers carbon dioxide from a cylinder. At one end of the hose there is a connector with contacts, a fitting for a gas hose, a hole for a "jacket" and a nut that fastens the entire connector to the counterpart. At the other end of the hose is the "holder" itself: a plastic handle with a niche for a push-button switch and a tube with an external thread, on which a tip is installed through which the wire exits - fig. 3.

(click to enlarge)

Most of the units of the device circuit are placed in a metal case on wheels (circled by a dashed line in the diagram), the welding voltage is removed from the contact bolts brought into the wall of this case, and the rest is placed like this, see fig. 4:

(click to enlarge)

- gas valve KL1, as well as C7, R11, R13, VT7, VT8, R14 are placed in a separate small case (also with wheels on one side), which also has a connector that commutates the above elements with the main board of the device;

- SA1 "Start" - a button located in the niche of the "holder" of the welder.

Note. The latest operating experience of the device showed that it is worth installing a 2-1 Ohm 2W resistor in the emitter circuit of the VT1 transistor to extend the life of the LEDs as part of optothyristors.

Literature

1. Vinogradov V.S. Equipment and technology of arc automatic and mechanized welding.: Textbook for prof. textbook Institutions. M.: Higher. School: Publishing Center "Academy", 1997.- 320 p. ill.
2. Ryutman Kh.Ya. Car repair.- M.: Patriot, 1992.-320 p., ill.

Author: Pomelov V.N.; Publication: cxem.net

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