The reliability of modern semi-automatic machines is often let down by the wire feed speed regulator of the semi-automatic welding machine; the circuit is not always reliable and the mechanical

some also often malfunction.

The malfunction of this unit leads to significant failures in working with the semi-automatic machine, loss of working time and hassle with replacing the welding wire. The wire at the exit from the tip gets stuck, so you have to remove the tip and clean the contact part for the wire. The malfunction is observed with any diameter of the welding wire used. Or a large feed may occur, when the wire comes out in large portions when the power button is pressed.

Malfunctions are often caused by the mechanical part of the wire feed regulator itself. Schematically, the mechanism consists of a pressure roller with an adjustable degree of wire pressure, a feed roller with two grooves for wire 0.8 and 1.0 mm. A solenoid is mounted behind the regulator, which is responsible for shutting off the gas supply with a delay of 2 seconds.

The feed regulator itself is very massive and is often simply attached to the front panel of the semi-automatic machine with 3-4 bolts, essentially hanging in the air. This leads to distortions of the entire structure and frequent malfunctions. Actually, it is quite simple to “cure” this drawback by installing some kind of stand under the wire feed regulator, thereby fixing it in the working position.

On factory-made semi-automatic machines in most cases (regardless of the manufacturer) carbon dioxide it is supplied to the solenoid through a dubious thin hose in the form of a cambric, which simply “steals” from cold gas and then cracks. This also causes work to stop and requires repairs. Based on their experience, experts advise replacing this supply hose with a car hose used to supply brake fluid from the reservoir to the brake master cylinder. The hose can withstand pressure perfectly and will serve indefinitely.

The industry produces semi-automatic machines with welding current about 160 A. This is sufficient when working with automotive iron, which is quite thin - 0.8-1.0 mm. If you have to weld, for example, elements made of 4 mm steel, then this current is not enough and the penetration of the parts is not complete. For these purposes, many craftsmen purchase an inverter, which, together with a semi-automatic device, can produce up to 180A, which is quite enough to guarantee a welded seam of parts.

Many people try with their own hands, through experiments, to eliminate these shortcomings and make the operation of the semi-automatic device more stable. Quite a lot of schemes and possible improvements to the mechanical part have been proposed.

One of these proposals. This is a modified and operationally tested wire feed speed regulator for a semi-automatic welding machine, a circuit proposed on an integrated stabilizer 142EN8B. Thanks to the proposed scheme of operation of the wire feed regulator, it delays the feed for 1-2 seconds after the gas valve is activated and brakes it as quickly as possible at the moment the power button is released.

The downside of the circuit is the decent power supplied by the transistor, heating the cooling radiator during operation to 70 degrees. But it all adds up reliable operation both the wire feed speed regulator itself and the entire semi-automatic device as a whole.

From this article you will learn where and for what welding processes an inverter semi-automatic machine is used, as well as what its disadvantages and advantages are.

What are diesel generators used for?

Three-phase diesel generators

The most powerful diesel generators always.

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Wire feed speed regulator for semi-automatic welding machine

On sale you can see many semi-automatic welding machines of domestic and foreign production used in the repair of car bodies. If you wish, you can save on costs by assembling a semi-automatic welding machine in a garage.

The welding machine kit includes a housing, in the lower part of which a single-phase or three-phase power transformer is installed, and above is a device for drawing the welding wire.

The device includes an electric motor direct current with a transmission mechanism for reducing speed, as a rule, an electric motor with a gearbox from a windshield wiper of a UAZ or Zhiguli car is used here. Copper-coated steel wire from the feed drum, passing through rotating rollers, enters the wire supply hose, at the exit the wire comes into contact with a grounded product, and the resulting arc welds the metal. To isolate the wire from atmospheric oxygen, welding occurs in an inert gas environment. To turn on the gas installed solenoid valve. When using a prototype of a factory semi-automatic machine, some shortcomings were identified that impede high-quality welding: premature failure of the output transistor of the electric motor speed controller circuit due to overload; the absence in the budget scheme of automatic engine braking upon a stop command - the welding current disappears when turned off, and the engine continues to feed wire for some time, this leads to excess wire consumption, the risk of injury, and the need to remove excess wire with a special tool.

In the laboratory of “Automation and Telemechanics” of the Irkutsk Regional DTT Center, a more modern wire feed regulator circuit has been developed, the fundamental difference of which from the factory ones is the presence of a braking circuit and a double supply of the switching transistor for the starting current with electronic protection.

Device characteristics:
1. Supply voltage 12-16 volts.
2. Electric motor power - up to 100 watts.
3. Braking time 0.2 sec.
4. Start time 0.6 sec.
5. Speed adjustment 80%.
6. Starting current up to 20 amperes.

The circuit diagram of the wire feed regulator includes a current amplifier based on a powerful field-effect transistor. A stabilized speed setting circuit allows you to maintain power in the load regardless of the mains supply voltage; overload protection reduces burning of the electric motor brushes during startup or jamming in the wire feeder and failure of the power transistor.

The voltage from the speed controller of the electric motor R3 through the limiting resistor R6 is supplied to the gate of the powerful field-effect transistor VT1. The speed controller is powered from the analog stabilizer DA1, through the current-limiting resistor R2. To eliminate interference possible from turning the slider of resistor R3, a filter capacitor C1 is introduced into the circuit.

Field-effect transistor VT1 is equipped with protection circuits: a resistor R9 is installed in the source circuit, the voltage drop across which is used to control the voltage at the gate of the transistor using the comparator DA2. At a critical current in the source circuit, the voltage through the trimming resistor R8 is supplied to control electrode 1 of the comparator DA2, the anode-cathode circuit of the microcircuit opens and reduces the voltage at the gate of transistor VT1, the speed of the electric motor M1 will automatically decrease.

To eliminate the operation of protection against pulse currents that occur when the motor brushes spark, a capacitor C2 is introduced into the circuit.
A wire feed motor with collector spark reduction circuits C3, C4, C5 is connected to the drain circuit of transistor VT1. A circuit consisting of diode VD2 with load resistor R7 eliminates reverse current pulses from the electric motor.

The two-color LED HL2 allows you to control the state of the electric motor; when the light is green, it is rotating, and when the light is red, it is braking.

The braking circuit is based on electromagnetic relay K1. The capacitance of filter capacitor C6 is chosen to be small - only to reduce vibrations of the armature of relay K1; a large value will create inertia when braking the electric motor. Resistor R9 limits the current through the relay winding when the power supply voltage is increased.

The principle of operation of braking forces, without the use of rotation reversal, is to load the reverse current of the electric motor when rotating by inertia, when the supply voltage is turned off, onto a constant resistor R8. The recovery mode - transferring energy back to the network allows you to stop the motor in a short time. At a complete stop, the speed and reverse current will be set to zero, this happens almost instantly and depends on the value of resistor R11 and capacitor C5. The second purpose of capacitor C5 is to eliminate burning of contacts K1.1 of relay K1. After supplying mains voltage to the regulator control circuit, relay K1 will close the electric motor power supply circuit K1.1, drawing the welding wire will resume.

The power source consists of a network transformer T1 with a voltage of 12-15 volts and a current of 8-12 amperes, the VD4 diode bridge is selected for 2 times the current. If the semi-automatic welding transformer has a secondary winding of the appropriate voltage, power is supplied from it.

The wire feed regulator circuit is made on printed circuit board made of single-sided fiberglass 136*40 mm in size, except for the transformer and motor, all parts are installed with recommendations for possible replacement. The field-effect transistor is installed on a radiator with dimensions 100 * 50 * 20.

Field effect transistor analogue of IRFP250 with a current of 20-30 Amperes and a voltage above 200 Volts. Resistors type MLT 0.125, R9, R11, R12 - wire-wound. Install resistor R3, R5 type SP-3 B. The type of relay K1 is indicated in the diagram or No. 711.3747-02 for a current of 70 Amperes and a voltage of 12 Volts, their dimensions are the same and are used in VAZ cars.

Comparator DA2, with a decrease in stabilization of speed and protection of the transistor, can be removed from the circuit or replaced with a zener diode KS156A. The VD3 diode bridge can be assembled using Russian diodes of type D243-246, without radiators.

The DA2 comparator has a complete analogue of the foreign-made TL431 CLP.
Electromagnetic valve for inert gas supply Em.1 is standard, with a supply voltage of 12 volts.

Adjusting the wire feed regulator circuit of a semi-automatic welding machine start by checking the supply voltage. Relay K1 should operate when voltage appears, producing a characteristic clicking sound from the armature.

By increasing the voltage at the gate of the field-effect transistor VT1 with the speed regulator R3, check that the speed begins to increase at the minimum position of the resistor R3 slider, if this does not happen, adjust the minimum speed with resistor R5 - first set the resistor R3 slider to the lower position, with a gradual increase in the value of resistor K5, the engine should reach minimum speed.

The scheme has been tested on different types electric motors with similar power, the braking time mainly depends on the mass of the armature, due to the inertia of the mass. The heating of the transistor and diode bridge does not exceed 60 degrees Celsius.

The printed circuit board is fixed inside the body of the semi-automatic welding machine, the engine speed control knob - R3 is displayed on the control panel along with indicators. turning on HL1 and two-color engine operation indicator HL2. Power is supplied to the diode bridge from a separate winding of a welding transformer with a voltage of 12-16 volts. The inert gas supply valve can be connected to capacitor C6, it will also turn on after mains voltage is applied. Power supply to power networks and electric motor circuits should be carried out using stranded wire in vinyl insulation with a cross-section of 2.5-4 mm2.

List of radioelements

Vladimir 02.22.2012 08:54 #

The circuit does not ensure the maintenance of stable engine speeds regardless of the load power and network voltage. To solve this problem, it is not enough to stabilize the gate voltage.
Limiting the current to 25A, according to the R9 rating, will not save anything. Even the resistor itself will dissipate 62.5 W. But not for long... There is no talk of a transistor.
Circuit R7, VD2 is meaningless.
There is no recovery mode in the scheme. Quote: “...consists in the load of the reverse current of the electric motor when rotating by inertia...” is simply a gem.
What is typical is that there is no photo of the assembled board...

Grigory T. 02/25/2012 13:37 #

Message from Vladimir

Limiting the current to 25A, according to the R9 rating, will not save anything.

What do you think of the fake R8 trimmer?
There are too many mistakes in the scheme to seriously discuss it.

Dmitry 02/26/2012 14:24 #

Yes, this circuit is completely crap, I assembled it a couple of months ago, but it was a waste of time to wire up the board, there is nothing good in it. I assembled part of the regulator from a power supply on LM358 and KT825, and I’m satisfied, the speed is controlled smoothly, and there is sufficient power at low speeds, the drawback is that it is necessary to remove heat from the transistor.

Yuri 03/21/2012 17:32 #

I struggled with setting up this circuit for several days. If the engine starts, then the speed is regulated normally, but starting at low speeds is a problem, there is not enough voltage, and if the variable is turned all the way out, then this is no longer adjusting the wire feed, but really just crap

Semi-automatic welding circuit diagram

On sale you can see many semi-automatic welding machines of domestic and foreign production, used in the repair of car bodies. If you wish, you can save on costs by assembling a semi-automatic welding machine in a garage.

Wire feed speed regulator for semi-automatic welding machine

The welding machine kit includes a housing, in the lower part of which a single-phase or three-phase power transformer is installed, and above is a device for drawing the welding wire.

The device includes a DC electric motor with a speed reduction transmission mechanism; as a rule, an electric motor with a gearbox from a UAZ or Zhiguli windshield wiper is used here. Copper-coated steel wire from the feed drum, passing through rotating rollers, enters the wire feed hose; at the exit, the wire comes into contact with a grounded workpiece, and the resulting arc welds the metal. To isolate the wire from atmospheric oxygen, welding occurs in an inert gas environment. An electromagnetic valve is installed to turn on the gas. When using a prototype of a factory semi-automatic machine, some shortcomings were identified that impede high-quality welding. This is a premature failure of the output transistor of the electric motor speed controller circuit due to overload and the absence in the budget circuit of an automatic engine braking system upon a stop command. When switched off, the welding current disappears, and the motor continues to feed wire for some time, which leads to excessive wire consumption, the risk of injury, and the need to remove excess wire with a special tool.

In the laboratory “Automation and Telemechanics” of the Irkutsk Regional CDTT, a more modern circuit of the wire feed regulator has been developed, the fundamental difference of which from the factory ones is the presence of a braking circuit and a double supply of the switching transistor for the starting current with electronic protection.

The braking circuit allows you to stop the engine rotation almost instantly.

The supply voltage is used from a power or separate transformer with a power consumption not lower than the maximum power of the wire drawing motor.

The circuit includes LEDs to indicate the supply voltage and the operation of the electric motor.

Device characteristics:

supply voltage, V - 12.16;
electric motor power, W - up to 100;
braking time, sec - 0.2;
start time, sec - 0.6;
adjustment
revolutions,% - 80;
starting current, A - up to 20.

Step 1. Description of the semiautomatic welding regulator circuit

The electrical circuit diagram of the device is shown in Fig. 1. The voltage from the speed controller of the electric motor R3 through the limiting resistor R6 is supplied to the gate of the powerful field-effect transistor VT1. The speed controller is powered from the analog stabilizer DA1, through the current-limiting resistor R2. To eliminate interference possible from turning the slider of resistor R3, a filter capacitor C1 is introduced into the circuit.
The HL1 LED indicates the on state of the welding wire feed regulator circuit.

Resistor R3 sets the feed speed of the welding wire to the arc welding site.

Trimmer resistor R5 allows you to select best option regulation of engine rotation speed depending on its power modification and power source voltage.

Diode VD1 in the circuit of voltage stabilizer DA1 protects the microcircuit from breakdown if the polarity of the supply voltage is incorrect.
Field-effect transistor VT1 is equipped with protection circuits: a resistor R9 is installed in the source circuit, the voltage drop across which is used to control the voltage at the gate of the transistor using comparator DA2. At a critical current in the source circuit, the voltage through the trimming resistor R8 is supplied to control electrode 1 of the comparator DA2, the anode-cathode circuit of the microcircuit opens and reduces the voltage at the gate of transistor VT1, the speed of the electric motor M1 will automatically decrease.

To eliminate the operation of protection against pulse currents that occur when the motor brushes spark, capacitor C2 is introduced into the circuit.
A wire feed motor with collector spark reduction circuits SZ, C4, C5 is connected to the drain circuit of transistor VT1. A circuit consisting of diode VD2 with load resistor R7 eliminates reverse current pulses from the electric motor.

The two-color LED HL2 allows you to control the state of the electric motor: when lit green - rotation, when lit red - braking.

The braking circuit is based on electromagnetic relay K1. The capacitance of filter capacitor C6 is selected to be small - only to reduce vibrations of the armature of relay K1; a large value will create inertia when the electric motor is braking. Resistor R9 limits the current through the relay winding when the power supply voltage is increased.

The principle of operation of braking forces, without the use of rotation reversal, is to load the reverse current of the electric motor when rotating by inertia, when the supply voltage is turned off, onto a constant resistor R11. The recovery mode - transferring energy back to the network allows you to stop the motor in a short time. At a complete stop, the speed and reverse current will be set to zero, this happens almost instantly and depends on the value of resistor R11 and capacitor C5. The second purpose of capacitor C5 is to eliminate burning of contacts K1.1 of relay K1. After supplying mains voltage to the regulator control circuit, relay K1 will close the electric motor power supply circuit K1.1, drawing the welding wire will resume.

The power source consists of a network transformer T1 with a voltage of 12.15 V and a current of 8.12 A, the diode bridge VD4 is selected for double current. If the semi-automatic welding transformer has a secondary winding of the appropriate voltage, power is supplied from it.

Step 2. Details of the semiautomatic welding regulator circuit

The wire feed regulator circuit is made on a printed circuit board made of single-sided fiberglass 136*40 mm in size (Fig. 2), except for the transformer and motor, all parts are installed with recommendations for possible replacement. The field-effect transistor is installed on a radiator with dimensions of 100*50*20 mm.

Field effect transistor analogue of IRFP250 with a current of 20. 30 A and a voltage above 200 V. Resistors type MLT 0.125; resistors R9, R11, R12 are wire-wound. Resistors R3, R5 should be installed as SP-ZB type. The type of relay K1 is indicated in the diagram or No. 711.3747-02 for a current of 70 A and a voltage of 12 V, their dimensions are the same and are used in VAZ cars.

The DA2 comparator has a complete analogue of the foreign-made TL431CLP.

Electromagnetic valve for inert gas supply Em.1 is standard, with a supply voltage of 12 V.

Step 3. Setting up the semi-automatic welding regulator circuit

The adjustment of the wire feed regulator circuit of a semi-automatic welding machine begins with checking the supply voltage. Relay K1 should operate when voltage appears, producing a characteristic clicking sound from the armature.

By increasing the voltage at the gate of field-effect transistor VT1 with the speed regulator R3, check that the speed begins to increase when the resistor R3 slider is at its minimum position; if this does not happen, adjust the minimum speed with resistor R5 - first set the slider of resistor R3 to the lower position, with a gradual increase in the value of resistor R5, the engine should reach the minimum speed.

Overload protection is set by resistor R8 during forced braking of the electric motor. When the field effect transistor is closed by the comparator DA2 due to overload, the HL2 LED will go out. Resistor R12 can be excluded from the circuit when the power supply voltage is 12.13 V.
The circuit has been tested on different types of electric motors, with similar power, the braking time mainly depends on the mass of the armature, due to the inertia of the mass. The heating of the transistor and diode bridge does not exceed 60°C.

The printed circuit board is fixed inside the body of the semi-automatic welding machine, the engine speed control knob - R3 is displayed on the control panel along with indicators: power on HL1 and two-color engine operation indicator HL2. Power to the diode bridge is supplied from a separate winding of the welding transformer with a voltage of 12.16 V. The inert gas supply valve can be connected to capacitor C6, it will also turn on after the mains voltage is applied. The power supply to the power networks and electric motor circuits should be carried out using a stranded wire in vinyl insulation with a cross-section of 2.5. 4 mm2.

Starting circuit of a semi-automatic welding machine

Characteristics of the semi-automatic welding machine:

supply voltage, V - 3 phases * 380;
primary phase current, A - 8.12;
secondary voltage idle move, B - 36. 42;
no-load current, A - 2.3;
no-load arc voltage, V - 56;
welding current, A - 40. 120;
voltage regulation, % — ±20;
ON duration, % - 0.

The wire is fed into the welding zone in a semi-automatic welding machine using a mechanism consisting of two steel rollers rotating in opposite directions by an electric motor. To reduce speed, the electric motor is equipped with a gearbox. From the conditions for smooth adjustment of the wire feed speed, the rotation speed of the DC electric motor is additionally changed by the semiconductor wire feed speed controller of the semiautomatic welding machine. An inert gas, argon, is also supplied to the welding zone to eliminate the effect of atmospheric oxygen on the welding process. The mains power supply for the semi-automatic welding machine is made from a single-phase or three-phase electrical network; a three-phase transformer is used in this design; recommendations for power supply from a single-phase network are indicated in the article.

Three-phase power allows the use of a smaller winding wire than when using a single-phase transformer. During operation, the transformer heats up less, voltage ripples at the output of the rectifier bridge are reduced, and the power line is not overloaded.

Step 1. Operation of the semi-automatic welding starting circuit

Switching the connection of power transformer T2 to the electrical network occurs using triac switches VS1. VS3 (Fig. 3). Choosing triacs instead of a mechanical starter allows you to eliminate emergency situations when contacts break and eliminates the sound from the “popping” of the magnetic system.
Switch SA1 allows you to disconnect the welding transformer from the network during maintenance work.

The use of triacs without radiators leads to their overheating and random switching on of the semi-automatic welding machine, so triacs must be equipped with budget radiators 50*50 mm.

It is recommended to equip the semi-automatic welding machine with a fan with a 220 V power supply; its connection is parallel to the network winding of transformer T1.
The three-phase transformer T2 can be used ready-made, with a power of 2.2.5 kW, or you can buy three transformers 220 * 36 V 600 VA, used for lighting basements and metal-cutting machines, connect them in a star-star configuration. When making a homemade transformer, the primary windings must have 240 turns of PEV wire with a diameter of 1.5. 1.8 mm, with three taps 20 turns from the end of the winding. The secondary windings are wound with a copper or aluminum busbar with a cross-section of 8.10 mm2, the number of PVZ wires is 30 turns.

Taps on the primary winding allow you to adjust the welding current depending on the mains voltage from 160 to 230 V.
The use of a single-phase welding transformer in the circuit allows the use of an internal electrical network used to power home electric furnaces with an installed power of up to 4.5 kW - the wire suitable for the outlet can withstand a current of up to 25 A, there is grounding. The cross-section of the primary and secondary windings of a single-phase welding transformer should be increased by 2.2.5 times in comparison with the three-phase version. A separate grounding wire is required.

Additional regulation of the welding current is carried out by changing the delay angle of the triacs. Using semiautomatic welding machines in garages and summer cottages does not require special network filters to reduce impulse noise. When using a semi-automatic welding machine at home, it should be equipped with an external noise filter.

Smooth control of the welding current is carried out using an electronic unit on a silicon transistor VT1 when the SA2 “Start” button is pressed - by adjusting the resistor R5 “Current”.

The T2 welding transformer is connected to the electrical network using the SA2 “Start” button located on the welding wire feed hose. The electronic circuit opens the power triacs through optocouplers, and the mains voltage is supplied to the network windings of the welding transformer. After voltage appears on the welding transformer, a separate wire feed unit is turned on, the inert gas supply valve opens and when the wire coming out of the hose touches the part being welded, an electric arc is formed and the welding process begins.

Transformer T1 is used for power supply electronic circuit starting the welding transformer.

When supplying mains voltage to the anodes of the triacs through an automatic three-phase circuit breaker SA1, transformer T1 powering the electronic starting circuit is connected to the line, the triacs are in the closed state at this time. The voltage of the secondary winding of transformer T1, rectified by the diode bridge VD1, is stabilized by the analog stabilizer DA1 for stable operation of the control circuit.

Capacitors C2, SZ smooth out the ripples of the rectified supply voltage of the starting circuit. The triacs are switched on using the key transistor VT1 and triac optocouplers U1.1. U1.3.

The transistor is opened by a voltage of positive polarity from the analog stabilizer DA1 through the “Start” button. The use of low voltage on the button reduces the likelihood of injury to the operator by high voltage in the electrical network in case of damage to the wire insulation. The current regulator R5 regulates the welding current within 20 V. Resistor R6 does not allow reducing the voltage on the network windings of the welding transformer by more than 20 V, at which the level of noise in the electrical network sharply increases due to distortion of the voltage sinusoid by triacs.

Triac optocouplers U1.1. U1.3 perform galvanic isolation of the electrical network from the electronic control circuit, allowing simple method adjust the opening angle of the triac: the greater the current in the optocoupler LED circuit, the smaller the cutoff angle and the greater the welding circuit current.
The voltage to the control electrodes of the triacs is supplied from the anode circuit through an optocoupler triac, a limiting resistor and a diode bridge, synchronously with the network phase voltage. Resistors in the optocoupler LED circuits protect them from overload at maximum current. Measurements showed that when starting at maximum welding current, the voltage drop across the triacs did not exceed 2.5 V.

If there is a large variation in the slope of the triacs, it is useful to shunt their control circuit to the cathode through a resistance of 3.5 kOhm.
An additional winding is wound on one of the rods of the power transformer to power the wire feed unit with voltage alternating current 12 V, the voltage to which must be supplied after turning on the welding transformer.

The secondary circuit of the welding transformer is connected to a three-phase DC rectifier using VD3 diodes. VD8. Installation of powerful radiators is not required. The circuit connecting the diode bridge with capacitor C5 is made with a copper bus with a cross section of 7 * 3 mm. Choke L1 is made of iron from a power transformer for tube TVs of the TS-270 type; the windings are first removed, and in their place a winding with a cross-section of at least 2 times the secondary is wound until it is filled. Place a gasket made of electrical cardboard between the halves of the transformer iron of the inductor.

Step 2. Installation of the semi-automatic welding starting circuit

The starting circuit (Fig. 3) is mounted on a circuit board (Fig. 4) measuring 156*55 mm, except for elements: VD3. VD8, T2, C5, SA1, R5, SA2 and L1. These elements are fixed to the body of the semi-automatic welding machine. The circuit does not contain indication elements; they are included in the wire feed unit: power indicator and wire feed indicator.

The power circuits are made of insulated wire with a cross-section of 4.6 mm2, the welding circuits are made of copper or aluminum busbar, the rest are made of vinyl insulated wire with a diameter of 2 mm.

The polarity of the connection of the holder should be selected based on the conditions of welding or surfacing when working with metal with a thickness of 0.3. 0.8 mm.

Step 3. Setting up the start-up circuit for the semi-automatic welding machine

Adjustment of the starting circuit of the semi-automatic welding machine begins with checking the voltage of 5.5 V. When you press the “Start” button on capacitor C5, the no-load voltage should exceed 50 V DC, and under load - at least 34 V.

At the triac cathodes, relative to the network zero, the voltage should not differ by more than 2.5 V from the voltage at the anode; otherwise, replace the triac or optocoupler of the control circuit.

If the mains voltage is low, switch the transformer to low voltage taps.

When setting up, you should follow safety precautions.

Download printed circuit boards:

Source: Radio Amateur 7 "2008

The pilot (yesterday, 01:32) wrote:

preference should be given to a motor with permanent magnets, since it has a pronounced dependence of the EMF on the rotor speed.

I would even say not just pronounced, but linear.

If we rotate the engine with something foreign, like a generator, then some voltage will appear at its terminals. If we apply the same voltage to this motor, then it will rotate at approximately the same speed as we rotated it. When the motor rotates, the back-EMF arising in the armature is directed counter to the supply voltage and they are compensated.

In a real motor, when the shaft is loaded, the speed decreases due to the voltage drop across the ohmic resistance of the winding; this resistance is, as it were, connected in series between the power source and the ideal motor. By the way, if we power a DC motor with permanent magnets from a current source, we get a stable torque on the shaft, this can also be useful. Yes, the resistance of the windings of the same motor from the wipers is very small and significantly less than the output resistance of a primitive source. With a good voltage stabilizer, it can be neglected. You can make a source with a negative output resistance equal to the resistance of the windings, this is done, for example, in cassette recorders, the stability will be better, but for our task this is, IMHO, unnecessary. Concerning feedback from the tachogenerator, then this task is not as simple as it seems at first glance.

Damn, what a stream of consciousness it turned out to be, sorry.

And the diagram in the topic does not inspire confidence in me.

#17 Pilot

Members

339 messages

City: Cherkasy region. Talnoye

Wire feed stabilization - diagram

Practice is a good thing, but without theory it is useless. I’ll try to explain in a simplified way why the engine decreases speed when the load on the shaft increases? According to the laws of physics, in order for an engine to deliver a certain power, it must consume the same power from the power source, taking into account Engine efficiency. Since the load on the engine is not constant over time (bending of the hose, sticking of the wire, etc.), we can conclude from this that the supply voltage should change proportionally, depending on the load and stable rotor speed. A stabilized voltage source does not meet these conditions. Based on the above, I developed a PWM engine speed stabilizer with rigid feedback, which meets all these requirements. The circuit is quite simple, although a little complicated to set up. Details can be found here http://www.chipmaker. __1#entry709142

#18 dan_ko

Members

1447 messages

City Dnepropetrovsk

Wire feed stabilization - diagram

The pilot (today, 14:42) wrote:

from this we can conclude that the supply voltage should change proportionally, depending on the load

I would not make such a conclusion.

The current consumed by the motor varies depending on the load. This changes the power consumption. Even if we make full feedback from the tachometer, we will be surprised to find that over the entire load range, at a constant speed, the voltage on the motor will change very slightly.

I will not discuss your scheme, so as not to create floods and flames.

What is a semi-automatic welding circuit?

Some people think that it is not worth buying expensive welding installations when they can be assembled with their own hands. Moreover, such installations can work no worse than factory ones and have fairly good quality indicators. In addition, if such a unit breaks down, you have the opportunity to quickly and independently fix the breakdown. But in order to assemble such a device, you should be thoroughly familiar with the basic principles of operation and constituent elements semi-welding machine.

Semi-automatic welding device.

Transformer for semi-welding machine

First of all, you need to decide on the type of semi-automatic welding machine and its power. The power of the semi-automatic device will be determined by the operation of the transformer. If the welding machine uses threads with a diameter of 0.8 mm, then the current flowing in them can be at the level of 160 amperes. After making some calculations, we decide to make a transformer with a power of 3000 watts. After the power for the transformer has been selected, its type should be selected. The best choice for such a device is a transformer with a toroidal core, on which the windings will be wound.

If you use the most popular W-shaped core, the semi-automatic machine will become much heavier, which will be a disadvantage for the welding machine as a whole, which will need to be constantly transferred to different objects. In order to make a transformer with a power of 3 kilowatts, you will need to wind a winding on a ring magnetic core. Initially, you should wind the primary winding, which starts with a voltage of 160 V in steps of 10 V and ends at 240 V. In this case, the wire must have a cross-section of at least 5 square meters. mm.

After winding the primary winding is completed, the second should be wound on top of it, but this time you need to use wire with a cross-section of 20 sq. mm. The voltage value on this winding will read 20 V. By creating this, it is possible to provide 6 stages of current regulation, one mode of standard operation of the transformer and two types of passive operation of the transformer.

Adjusting the semi-welding machine

Semiautomatic welding machine with thyristor control.

Today, there are 2 types of current regulation in a transformer: on the primary and secondary windings. The first is the regulation of the current on the primary winding, which is carried out using a thyristor circuit, which often has many disadvantages. One of these is the periodic increase in the pulsation of the welding machine and the phase transition of such a circuit from the thyristor to the primary winding. Adjusting the current through the secondary winding also has a number of disadvantages when using a thyristor circuit.

In order to eliminate them, you will have to use compensating materials, which will make the assembly much more expensive, and besides, the device will become much heavier. Having analyzed all these factors, we can come to the conclusion that the current should be adjusted through the primary winding, and the choice of the circuit to be used remains with the creator. To provide necessary adjustment On the secondary winding you need to install a smoothing choke, which will be combined with a capacitor with a capacity of 50 mF. This setting should be done regardless of the circuit you are using to ensure efficient and uninterrupted operation welding machine.

Adjusting the welding wire feed

Diagram of a transformer with primary and secondary windings.

As with many other welding machines, it is best to use pulse width modulation with feedback control. What does PWM do? This type of modulation will allow you to normalize the speed of the wire, which will be adjusted and set depending on the friction created by the wire and the fit of the device. In this case, there is a choice between feeding the PWM regulator, which can be done by separate winding or powering it from a separate transformer.

With the latter option it will be more expensive scheme, but this difference in cost will be insignificant, but at the same time the device will gain a little weight, which is a significant disadvantage. Therefore, it is best to use the first option. But if it is necessary to weld extremely carefully, at a low current, then, consequently, the voltage and current passing through the wire will be just as small. In the case of a large current value, the winding must create an appropriate voltage value and transfer it to your regulator.

Thus, the additional winding can fully satisfy the needs of the potential user for the maximum current value. Having familiarized yourself with this theory, we can conclude that installing an additional transformer is unnecessary expense money, and the desired mode can always be maintained with additional winding.

Calculation of the diameter of the drive wheel for the welding wire feeder

Calculation diagram of a welding transformer.

Through practice, it was determined that the unwinding speed of welding wire can reach values from 70 centimeters to 11 meters per minute, with a diameter of the wire itself of 0.8 mm. The subordinate value and the speed of rotation of the parts are unknown to us, so we should make calculations based on the available data on the unwinding speed. To do this, it is best to do a small experiment, after which it will be possible to determine required quantity rpm Turn on the equipment at full power and count how many revolutions it makes per minute.

To accurately capture the rotation, anchor a match or tape so you know where the circle ends and begins. After your calculations are done, you can find out the radius using the formula familiar from school: 2piR=L, where L is the length of the circle, that is, if the device makes 10 revolutions, you need to divide 11 meters by 10, and you get an unwinding of 1.1 meters. This will be the unwinding length. R is the radius of the anchor, which needs to be calculated. The number “pi” should be known from school; its value is 3.14. Let's give an example. If we counted 200 revolutions, then by calculation we determine the number L = 5.5 cm. Next, we calculate R=5.5/3.14*2= 0.87 cm. So, the required radius will be 0.87 cm.

Functionality of the semi-welding machine

Characteristics of welding transformers.

It is best to do it with a minimum set of functions, such as:

The initial supply of carbon dioxide to the tube, which will allow you to first fill the tube with gas and only then supply a spark.
After pressing the button, you should wait about 2 seconds, after which the wire feed will automatically turn on.
Simultaneously turning off the current and wire feeding when you release the control button.
After everything done above, it is necessary to stop the gas supply with a delay of 2 seconds. This is done in order to prevent the metal from oxidizing after cooling.

In order to assemble a welding wire feed motor, you can use a windshield wiper gearbox from many domestic cars. At the same time, do not forget that the minimum amount of wire that should be unwound per minute is 70 centimeters, and the maximum is 11 meters. These values must be used as a guide when choosing an anchor for reeling out wire.

It is best to choose a valve for gas supply among water supply mechanisms from the same domestic cars. But it is very important to ensure that this valve does not begin to leak after some time, which is very dangerous. If you choose everything correctly and correctly, the device under normal operating conditions can last about 3 years, and you will not need to repair it many times, since it is quite reliable.

Semiautomatic welding machine: diagram

The circuit of the semi-automatic welding machine provides all the functionality and will make the semi-automatic welding machine very convenient to use. To install manual mode, switch relay SB1 must be closed. After you press the SA1 control button, activate switch K2, which, using its connections K2.1 and K2.3, will turn on the first and third key.

Next, the first key activates the supply of carbon dioxide, while key K1.2 begins to turn on the power circuit of the semi-automatic welding machine, and K1.3 completely turns off the engine brake. Moreover, during this process, relay K3 begins to interact with its contacts K3.1, which by its action turns off the engine power circuit, and K3.2 unbends K5. K5 in the open state provides a delay in turning on the device for two seconds, which must be selected using resistor R2. All these actions take place with the engine turned off, and only gas is supplied to the tube. After all this, the second capacitor, with its impulse, turns off the second switch, which serves to delay the supply of welding current. After which the welding process itself begins. Reverse process when released, SB1 is similar to the first, while providing a delay of 2 seconds to turn off the gas supply to the semi-automatic welding machine.

Ensuring automatic mode of semi-automatic welding machine

Device diagram welding inverter.

First, you should familiarize yourself with what automatic mode is for. For example, it is necessary to weld a rectangular layer of a metal alloy, and the work must be perfectly smooth and symmetrical. If you use manual mode, the plate along the edges will have a seam of varying thickness. This will cause additional difficulties, since it will be necessary to level it to the desired size.

If you use automatic mode, then the possibilities increase slightly. To do this, you need to adjust the welding time and current strength, and then try your welding on some unnecessary object. After checking, you can make sure that the seam is suitable for welding the structure. Then we turn on the desired mode again and begin welding your metal sheet.

When you turn on the automatic mode, use the same SA1 button, which will carry out all processes similarly manual welding, with only one discrepancy that to put it into operation you will not need to hold down this button, and all activation will be provided by the C1R1 chain. This mode will take from 1 to 10 seconds to be fully operational. The operation of this mode is very simple; to do this, you need to press the control button, after which welding starts.

After the time specified by resistor R1 has passed, welding machine will turn off the flame on its own.

The welding machine kit includes a housing, in the lower part of which a single-phase or three-phase power transformer is installed, and above is a device for drawing the welding wire.

The device includes a DC electric motor with a transmission mechanism for reducing speed; as a rule, an electric motor with a gearbox from a windshield wiper of a UAZ or Zhiguli car is used here. Copper-coated steel wire from the feed drum, passing through rotating rollers, enters the wire supply hose, at the exit the wire comes into contact with a grounded product, and the resulting arc welds the metal. To isolate the wire from atmospheric oxygen, welding occurs in an inert gas environment. An electromagnetic valve is installed to turn on the gas. When using a prototype of a factory semi-automatic machine, some shortcomings were identified that impede high-quality welding: premature failure of the output transistor of the electric motor speed controller circuit due to overload; the absence in the budget scheme of an automatic engine braking system upon a stop command - the welding current disappears when switched off, and the engine continues to feed wire for some time, this leads to excess wire consumption, the risk of injury, and the need to remove excess wire with a special tool.

In the laboratory of "Automation and Telemechanics" of the Irkutsk Regional DTT Center, a more modern wire feed regulator circuit has been developed, the fundamental difference of which from the factory ones is the presence of a braking circuit and a double supply of the switching transistor for the starting current with electronic protection.

The braking circuit allows you to stop the engine rotation almost instantly.
The supply voltage is used from a power or separate transformer with a power consumption not lower than the maximum power of the wire drawing motor.
The circuit includes LEDs to indicate the supply voltage and the operation of the electric motor.

The HL1 LED indicates the on state of the welding wire feed regulator circuit.
Resistor R3 sets the feed speed of the welding wire to the arc welding site.

Trimmer resistor R5 allows you to select the optimal option for regulating engine speed depending on its power modification and power source voltage.

Diode VD1 in the circuit of voltage stabilizer DA1 protects the microcircuit from breakdown if the polarity of the supply voltage is incorrect.

The two-color LED HL2 allows you to control the state of the electric motor; when the light is green, it is rotating, and when the light is red, it is braking.

The wire feed regulator circuit is made on a printed circuit board made of single-sided fiberglass 136*40 mm in size; except for the transformer and motor, all parts are installed with recommendations for possible replacement. The field-effect transistor is installed on a radiator with dimensions 100 * 50 * 20.

Field effect transistor analogue of IRFP250 with a current of 20-30 Amperes and a voltage above 200 Volts. Resistors type MLT 0.125, R9, R11, R12 - wire. Install resistor R3, R5 type SP-3 B. The type of relay K1 is indicated in the diagram or No. 711.3747-02 for a current of 70 Amperes and a voltage of 12 Volts, their dimensions are the same and are used in VAZ cars.

The DA2 comparator has a complete analogue of the foreign-made TL431 CLP.
Electromagnetic valve for inert gas supply Em.1 is standard, with a supply voltage of 12 volts.

The circuit has been tested on different types of electric motors, with similar power, the braking time mainly depends on the mass of the armature, due to the inertia of the mass. The heating of the transistor and diode bridge does not exceed 60 degrees Celsius.

The printed circuit board is fixed inside the body of the semi-automatic welding machine, the engine speed control knob - R3 is displayed on the control panel along with indicators: power on HL1 and two-color engine operation indicator HL2. Power is supplied to the diode bridge from a separate winding of a welding transformer with a voltage of 12-16 volts. The inert gas supply valve can be connected to capacitor C6, it will also turn on after mains voltage is applied. Power supply to power networks and electric motor circuits should be carried out using stranded wire in vinyl insulation with a cross-section of 2.5-4 mm2.

List of radioelements

Designation	Type	Denomination	Quantity	Note	My notepad
DA1	Linear regulator	MC78L06A	1		To notepad
DA2	Chip	KR142EN19	1		To notepad
VT1	MOSFET transistor	IRFP260	1		To notepad
VD1	Diode	KD512B	1		To notepad
VD2	Rectifier diode	1N4003	1		To notepad
VD3	Diode bridge	KVJ25M	1		To notepad
C1, C2		100uF 16V	2		To notepad
C3, C4	Capacitor	0.1 µF	2	at 63V	To notepad
C5	Electrolytic capacitor	10 µF	1	at 25V	To notepad
C6	Electrolytic capacitor	470uF	1	at 25V	To notepad
R1, R2, R4, R6, R10	Resistor	1.2 kOhm	4	0.25W	To notepad
R3	Variable resistor	3.3 kOhm	1		To notepad
R5	Trimmer resistor	2.2 kOhm	1		To notepad
R7	Resistor	470 Ohm	1	0.25W	To notepad
R8	Trimmer resistor	6.8kOhm	1		To notepad
R9	Precision resistor

Some people think that it is not worth buying expensive welding installations when they can be assembled with their own hands. Moreover, such installations can work no worse than factory ones and have fairly good quality indicators. In addition, if such a unit breaks down, you have the opportunity to quickly and independently fix the breakdown. But in order to assemble such a device, you should be thoroughly familiar with the basic operating principles and components of a semi-welding machine.

Transformer for semi-welding machine

Adjusting the semi-welding machine

Today, there are 2 types of current regulation in a transformer: on the primary and secondary windings. The first is the regulation of the current on the primary winding, carried out using a thyristor circuit, which often has many disadvantages. One of these is the periodic increase in the pulsation of the welding machine and the phase transition of such a circuit from the thyristor to the primary winding. Adjusting the current through the secondary winding also has a number of disadvantages when using a thyristor circuit.

In order to eliminate them, you will have to use compensating materials, which will make the assembly much more expensive, and besides, the device will become much heavier. Having analyzed all these factors, we can come to the conclusion that the current should be adjusted through the primary winding, and the choice of the circuit to be used remains with the creator. To ensure the necessary adjustment on the secondary winding, you need to install a smoothing choke, which will be combined with a capacitor with a capacity of 50 mF. This installation should be done regardless of the circuit you use, which will ensure efficient and uninterrupted operation of the welding machine.

Adjusting the welding wire feed

The latter option will result in a more expensive scheme, but this difference in cost will be insignificant, but at the same time the device will gain a little weight, which is a significant disadvantage. Therefore, it is best to use the first option. But if it is necessary to weld extremely carefully, at a low current, then, consequently, the voltage and current passing through the wire will be just as small. In the case of a large current value, the winding must create an appropriate voltage value and transfer it to your regulator.

Thus, the additional winding can fully satisfy the needs of the potential user for the maximum current value. Having become familiar with this theory, we can conclude that installing an additional transformer is an extra waste of money, and the desired mode can always be maintained with an additional winding.

Calculation of the diameter of the drive wheel for the welding wire feeder

Through practice, it was determined that the unwinding speed of welding wire can reach values from 70 centimeters to 11 meters per minute, with a diameter of the wire itself of 0.8 mm. The subordinate value and the speed of rotation of the parts are unknown to us, so we should make calculations based on the available data on the unwinding speed. To do this, it is best to do a small experiment, after which it is possible to determine the required number of revolutions. Turn on the equipment at full power and count how many revolutions it makes per minute.

Functionality of the semi-welding machine

It is best to do it with a minimum set of functions, such as:

The initial supply of carbon dioxide to the tube, which will allow you to first fill the tube with gas and only then supply a spark.
After pressing the button, you should wait about 2 seconds, after which the wire feed will automatically turn on.
Simultaneously turning off the current and wire feeding when you release the control button.
After everything done above, it is necessary to stop the gas supply with a delay of 2 seconds. This is done in order to prevent the metal from oxidizing after cooling.

Semiautomatic welding machine: diagram

The circuit of the semi-automatic welding machine provides all the functionality and will make the semi-automatic welding machine very convenient to use. In order to set the manual mode, switch relay SB1 must be closed. After you press the SA1 control button, activate switch K2, which, using its connections K2.1 and K2.3, will turn on the first and third key.

Next, the first key activates the supply of carbon dioxide, while key K1.2 begins to turn on the power circuit of the semi-automatic welding machine, and K1.3 completely turns off the engine brake. Moreover, during this process, relay K3 begins to interact with its contacts K3.1, which by its action turns off the engine power circuit, and K3.2 unbends K5. K5 in the open state provides a delay in turning on the device for two seconds, which must be selected using resistor R2. All these actions take place with the engine turned off, and only gas is supplied to the tube. After all this, the second capacitor, with its impulse, turns off the second switch, which serves to delay the supply of welding current. After which the welding process itself begins. The reverse process when releasing SB1 is similar to the first, while providing a 2-second delay to turn off the gas supply to the semi-automatic welding machine.

Ensuring automatic mode of semi-automatic welding machine

When you turn on the automatic mode, you use the same SA1 button, which will carry out all processes similar to manual welding, with the only discrepancy that to put it into operation you will not need to hold down this button, and all activation will be provided by the C1R1 chain. This mode will take from 1 to 10 seconds to be fully operational. The operation of this mode is very simple; to do this, you need to press the control button, after which welding starts.

After the time set by resistor R1 has passed, the welding machine itself will turn off the flame.

A good owner must have a semi-automatic welding machine, especially owners of cars and private property. With him you can always minor work do it yourself. If you need to weld a machine part, make a greenhouse or create some kind of metal structure, then such a device will become an indispensable assistant in private farming. Here a dilemma arises: buy or make it yourself. If you have an inverter, it’s easier to do it yourself. It will cost much less than buying in a retail chain. True, you will at least need basic knowledge on basic electronics, availability the necessary tool and desire.

Making a semi-automatic machine from an inverter with your own hands

Structure

Convert the inverter into a semi-automatic welding machine for welding thin steel (low-alloy and corrosion-resistant) and aluminum alloys It’s not difficult to do it yourself. You just need to have a good understanding of the intricacies of the work ahead and delve into the nuances of manufacturing. An inverter is a device that serves to lower the electrical voltage to the required level to power the welding arc.

The essence of the semi-automatic welding process in a protective gas environment is as follows. Electrode wire is supplied at a constant speed to the arc combustion zone. Shielding gas is supplied to the same area. Most often - carbon dioxide. This guarantees a high-quality weld, which is not inferior in strength to the metal being joined, while there are no slags in the joint, since the weld pool is protected from negative influence air components (oxygen and nitrogen) with protective gas.

The kit of such a semi-automatic device should include the following elements:

current source;
welding process control unit;
wire feed mechanism;
shielding gas supply hose;
carbon dioxide cylinder;
torch gun:
spool of wire.

Welding station design

Principle of operation

When connecting the device to an electric network, alternating current is converted into direct current. This requires a special electronic module, a high-frequency transformer and rectifiers.

For quality welding work It is necessary that the future device has parameters such as voltage, current and welding wire feed speed in a certain balance. This is facilitated by the use of an arc power source that has a rigid current-voltage characteristic. The length of the arc is determined by a rigidly specified voltage. The wire feed speed controls the welding current. This must be remembered in order to obtain from the device best results welding

The easiest way to use circuit diagram from Sanych, who long ago made such a semi-automatic machine from an inverter and successfully uses it. It can be found on the Internet. Many home craftsmen not only made a semi-automatic welding machine with their own hands using this scheme, but also improved it. Here is the original source:

Diagram of a semi-automatic welding machine from Sanych

Semi-automatic Sanych

To make the transformer, Sanych used 4 cores from TS-720. The primary winding was wound with copper wire Ø 1.2 mm (number of turns 180+25+25+25+25), for the secondary winding I used an 8 mm 2 busbar (number of turns 35+35). The rectifier was assembled using a full-wave circuit. For the switch I chose a paired biscuit. I installed the diodes on the radiator so that they would not overheat during operation. The capacitor was placed in a device with a capacity of 30,000 microfarads. The filter choke was made on a core from TS-180. The power part is put into operation using a TKD511-DOD contactor. The power transformer is installed TS-40, rewound to a voltage of 15V. The roller of the broaching mechanism in this semi-automatic machine has a Ø 26 mm. It has a guide groove 1 mm deep and 0.5 mm wide. The regulator circuit operates at a voltage of 6V. It is sufficient to ensure optimal feeding of the welding wire.

How other craftsmen improved it, you can read messages on various forums dedicated to this issue and delve into the nuances of manufacturing.

Inverter setup

To provide quality work semi-automatic with small dimensions, it is best to use toroidal type transformers. They have the highest efficiency.

The transformer for operation of the inverter is prepared as follows: it must be wrapped with a copper strip (40 mm wide, 30 mm thick), protected with thermal paper, of the required length. The secondary winding is made of 3 layers of sheet metal, insulated from each other. To do this, you can use fluoroplastic tape. The ends of the secondary winding at the output must be soldered. In order for such a transformer to operate smoothly and not overheat, it is necessary to install a fan.

Transformer winding diagram

Work on setting up the inverter begins with de-energizing the power section. Rectifiers (input and output) and power switches must have radiators for cooling. Where the radiator is located, which heats up the most during operation, it is necessary to provide a temperature sensor (its readings during operation should not exceed 75 0 C). After these changes, the power section is connected to the control unit. When switched on. The network indicator should light up. You need to check the pulses using an oscilloscope. They should be rectangular.

Their repetition rate must be in the range of 40 ÷ 50 kHz, and they must have a time interval of 1.5 μs (the time is adjusted by changing the input voltage). The indicator should show at least 120A. It would not be superfluous to check the device under load. This is done by inserting a 0.5 ohm load rheostat into the welding leads. It must withstand a current of 60A. This is checked using a voltmeter.

A properly assembled inverter when performing welding work makes it possible to regulate the current in a wide range: from 20 to 160A, and the choice of operating current depends on the metal that needs to be welded.

For making an inverter with my own hands You can take a computer unit, which must be in working order. The body needs to be strengthened by adding stiffeners. It is mounted in electronic part, made according to Sanych’s scheme.

Wire feeding

Most often, such home-made semi-automatic machines provide the possibility of feeding welding wire Ø 0.8; 1.0; 1.2 and 1.6 mm. Its feeding speed must be adjusted. The feeding mechanism together with the welding torch can be purchased at a retail chain. If desired and available necessary details it is quite possible to do it yourself. Savvy innovators use an electric motor from car wipers, 2 bearings, 2 plates and a Ø 25 mm roller for this. The roller is installed on the motor shaft. Bearings are attached to the plates. They press themselves against the roller. Compression is carried out using a spring. The wire passes along special guides between the bearings and the roller and is pulled.

All components of the mechanism are installed on a plate with a thickness of at least 8-10 mm, made of textolite, and the wire should come out in the place where the connector connecting to the welding sleeve is installed. A coil with the required Ø and grade of wire is also installed here.

Pulling mechanism assembly

You can make a homemade burner with your own hands, using the figure below, where its components are shown clearly in disassembled form. Its purpose is to close the circuit and provide the supply of shielding gas and welding wire.

Homemade burner device

However, those who want to quickly produce a semi-automatic gun can buy a ready-made gun in a retail chain along with sleeves for supplying shielding gas and welding wire.

Balloon

To supply shielding gas to the combustion zone of the welding arc, it is best to purchase a standard type cylinder. If you use carbon dioxide as a shielding gas, you can use a fire extinguisher cylinder by removing the speaker from it. It must be remembered that it requires a special adapter, which is needed to install the reducer, since the threads on the cylinder do not match the threads on the neck of the fire extinguisher.

Semi-automatic with your own hands. Video

You can learn about the layout, assembly, and testing of a homemade semi-automatic machine from this video.

A do-it-yourself inverter semi-automatic welding machine has undoubted advantages:

cheaper than store-bought counterparts;
compact dimensions;
the ability to weld thin metal even in hard-to-reach places;
will become the pride of the person who created it with his own hands.

some also often malfunction.

On factory-made semi-automatic machines, in most cases (regardless of the manufacturer), carbon dioxide is supplied to the solenoid through a dubious thin hose in the form of a cambric, which simply “blews” from the cold gas and then cracks. This also causes work to stop and requires repairs. Based on their experience, experts advise replacing this supply hose with a car hose used to supply brake fluid from the reservoir to the brake master cylinder. The hose can withstand pressure perfectly and will serve indefinitely.

The industry produces semi-automatic machines with a welding current of about 160 A. This is sufficient when working with automotive iron, which is quite thin - 0.8-1.0 mm. If you have to weld, for example, elements made of 4 mm steel, then this current is not enough and the penetration of the parts is not complete. For these purposes, many craftsmen purchase an inverter, which, together with a semi-automatic device, can produce up to 180A, which is quite enough to guarantee a welded seam of parts.

The downside of the circuit is the decent power supplied by the transistor, heating the cooling radiator during operation to 70 degrees. But all this is plus the reliable operation of both the wire feed speed regulator itself and the entire semi-automatic machine as a whole.