How to make a semi-automatic machine using inverter welding

Do-it-yourself semi-automatic inverter

A semi-automatic welding device for household needs can be purchased ready-to-use or completely assembled with your own hands. A homemade semi-automatic machine will cost the performer much less, but its assembly will require certain skills in working with electrical equipment. The appearance of such a welded device is shown in the figure below.

Appearance of a homemade semi-automatic machine

We recommend that everyone who wants to make a semi-automatic machine from an inverter with their own hands first familiarize themselves with the structure of this unit and the operating features of the modules included in it.

What is needed to remake an inverter

Before making a semi-automatic welding machine with your own hands, you will need to prepare the following functional modules and spare parts that provide the required complete set of prefabricated equipment:

• An old inverter unit designed for a welding current of about 150 Amps;
• Another working unit of the future semi-automatic device is the so-called “burner”;
• A special feeding mechanism, with the help of which it will be possible to organize the delivery of welding wire to the place of work;
• Hoses that supply wire and shielding gas to a homemade welding unit (more precisely, to the area where work operations are performed);
• A coil redesigned for new needs with a special wire placed on it;
• A separate electronic module that controls the functioning of the entire home-made device (including the converter transformer).

The complete set of components and modules required for the semi-automatic machine can be found in the figure below.

Unit design

Do-it-yourself spotter from a welding machine

Let's look at the most important parts of units made by hand from an inverter in more detail.

Consumable supply unit and burner

When equipping with spare parts, special attention should be paid to a thorough modification of the wire feeder, which will have to move inside the flexible hose.

To obtain a high-quality and neat weld, the wire feed speed must be synchronized with the melting rate of its working part.

Since semi-automatic welding allows the use of several types of wire, made of different materials and having different diameters, its flow rate must necessarily be variable. It is this opportunity that should be provided by the so-called “supply” of consumables, which is organized in accordance with the general requirements for any inverter unit.

When setting up a semi-automatic circuit, consumable wire with sections of 0.8, 1.0, 1.2 and 1.6 mm is most often used. Immediately before starting work, it is wound on pre-prepared reels, which are fixed to the elements of the unit using simple fasteners. Semi-automatic welding involves feeding the wire “self-propelled”, which significantly reduces the time of all operations and increases the efficiency of these procedures.

The torch used in a semi-automatic machine can be taken entirely from a non-working welding unit of the same type or made independently at home. Let’s immediately make a reservation that making a burner with your own hands is a very difficult task, requiring the performer to have certain experience and skills in the manufacture of such devices.

Electronic control module

The electrical circuit of the semi-automatic welding machine is shown in the figure below.

Electronic circuit (control unit)

The basic element of the semi-automatic control unit is the microcontroller, which is responsible for selecting the load mode and stabilizing the output current. In addition, the electronic unit includes the following mandatory components and parts:

• Rectifier bridge on high power semiconductor diodes;
• Key transistor circuits;
• Additional winding transformer;
• Correction chokes and inductors.

Particular attention in the composition of the electronic module should be paid to winding inductive products.

A simplified version of the inverter unit is known, which is usually called the “device from Sanych”. Its diagram is shown in the figure below.

Simplified electronic module diagram

Transformer

Another critical component of a semi-automatic machine, made with your own hands from an old welding device, is a transformer, which can be taken from the same inverter (subject to minor modifications).

To ensure the required characteristics of the inverter transformer, which are completely suitable for a semi-automatic device, it is necessary to rewind the old primary coil with a copper strip coated with a layer of heat-resistant paper.

Important! Such transformers cannot be wound with ordinary thick-section copper wire, since they will become very hot under high current loads.

The secondary winding of the old transformer product should also be slightly modified. To do this, you will need to perform the following operations:

• First you need to wind a coil consisting of 3 layers of tin strips, each of which is insulated with fluoroplastic tape;
• Next, the ends of the old and newly wound windings need to be soldered, which will ensure high conductivity of the entire coil;
• It is also necessary to provide a small fan in the set of elements from which the semi-automatic design is assembled (it is intended for additional cooling of the device).

A fan from a failed old PC can be used as such a cooling device installed in welding units.

Assembly of the unit

DIY wind generator from a car generator

Before making a semi-automatic machine with your own hands, be sure to check all the necessary parts of the old inverter. In addition, in order to improve the thermal conditions of the future device, it is necessary to provide additional radiators on which rectifiers and power diode switches are mounted (photo below).

Power switches on radiators

Additional Information. In the spaces where radiator units are to be located, it is necessary to provide thermal sensors that record the temperature in this part of the device.

After completing all of the above procedures, you should begin mating the power module with the electronic control unit, after which you can try to connect it to the network and check its operation.

Inverter setup

Do-it-yourself gasoline generator

To carry out this mandatory procedure, first of all, it is necessary to connect the probes of an oscilloscope to the output terminals of the inverter converter, through which it will be possible to examine the shape of the intermediate signals.

Note! Electrical pulses with a frequency of about 40-50 kHz should be observed on the screen of the oscilloscope device (see the figure below).

Diagrams of voltage at the output of the converter

The time between individual bursts of such pulses should be equal to 1.5 μs (it can be adjusted by changing the input voltage). The amount of control potential supplied to the input of the converter is usually measured using an electronic voltmeter.

In the process of setting up the conversion system, it is also necessary to monitor the shape of the pulses observed at the output, which should approach rectangular with rises lasting no more than 500 ns. If all the above parameters comply with the standard values, you can proceed to setting up the load part of the inverter device.

The maximum current generated at the output of a working unit should have a value of about 120 Amperes (its value can be measured using special current clamps). In addition to the current component, after putting the device into operation, it is necessary to monitor the temperature sensors installed in the area where the radiators are located.

At the final stage of putting the device into operation, it is necessary to check its functionality under load. To do this, a sufficiently “powerful” rheostat with an active resistance of about 0.5 Ohm should be connected to the welding wires.

Important! This adjusting device must be designed for currents of at least 60 Amperes, which are controlled using an ammeter built into the device.

If the rheostat selected for adjustment does not provide the required current value, its nominal resistance should be selected experimentally.

Testing a semi-automatic device in operation

After starting the self-assembled semi-automatic device, its indicator panel should display a current value corresponding to the operating value of 120 Amperes. At the same time, you should check the readings of the sensors installed on the cooling radiators of the homemade product (the temperature in their area of ​​​​action should not exceed 100 degrees).

You will also need to check the adjustment range of the output (load) current, which cannot be less than 20-160 Amperes.

In conclusion, we note that a semi-automatic machine, made by hand in compliance with all the rules discussed in this review, will be able to serve its owner for quite a long time. Its performance and reliability will largely depend on the quality of the components used and the reliability of their assembly.

Source: https://amperof.ru/elektropribory/poluavtomat-iz-invertora.html

A site for those who love cars and are not afraid of wrenches

MMA inverter

This article begins a new section “Tools and Devices”, and the article will be somewhat unusual, that is, it will not be about what and how to make, but on the contrary, what should not be done.

Thanks to the amazing labor productivity of the inhabitants of the Celestial Empire and the affordable cost, welding machines - “inverters” have firmly established themselves in the garages of many car owners.

And for good reason: small size, light weight, wide and smooth current adjustment range, “soft” arc, low power consumption make this welding machine an invaluable assistant in many cases, but not always, a car “tin” is often too delicate for electrode welding .

And then thoughts begin to arise in the inquisitive minds of car enthusiasts: what if we add a burner, draw wire and convert the “inverter” into a “semi-automatic” at low cost. I’ll say right away that this option will not work, and such an addition to a conventional welding machine on a transformer will also not work. Why? Read on.

Semi-automatic torch and welding wire

In order not to be unfounded: I have a DC welding machine on a transformer in the garage, also a few years ago I made my own semi-automatic machine (also a transformer one, which I use successfully), and this year I purchased an inverter welding machine (it’s a little hard to carry the transformer yourself).

I decided to test this possibility “empirically”, especially since everything necessary is available and no costs are needed.

I turned off the transformer in the “semi-automatic” machine, applied power from the “inverter”, tried it. To be honest, I tried it in different modes, adjusted the current, changed the wire feed speed, welded with gas and without it a normal seam did not come out, it turned out to put it mildly “shit”.

Now a little theory. There is no way without this, but I will try to be as simple and brief as possible.

Types or types of welding.

MMA ( Manual Metal Arc ). The most common type of welding is manual welding with flux-coated stick electrodes; by the way, this technology was developed by our compatriot N.G. Slavyanov.

TIG ( Tungsten Inert Gas ). Welding with a non-consumable (tungsten or graphite) electrode in a protective inert gas environment (argon-arc welding). Invented by N.N. Benardos.

MIG ( Mechanical Inert Gas ). Mechanized supply of electrode material (semi-automatic or automatic) in an inert gas environment (argon, helium).

MAG ( Mechanical Active Gas ). Mechanized supply of electrode material (semi-automatic or automatic) in an active (carbon dioxide) gas environment. Which interests us most. By the way, alloyed wire (we use copper-bonded wire) was also invented by our compatriots K.V. Lyubavsky and N.M. Novozhilov.

Now let's figure out how MMA and MAG power supplies differ, and why they cannot be used one instead of the other.

First, let's look at the conditions for the existence of an electric arc used in welding. In the above graph it is noticeable that

that the current-voltage characteristic of the arc (volt-ampere characteristic) has three distinct sections:

• descending section - which corresponds to a low current density,
• horizontal section – with average current density
• ascending section - which corresponds to a high current density.

So, during MMA welding , the arc burning process occurs in the middle section of the current-voltage characteristic, preferably in the first third of it, while the arc ignites easily, is kept stable, the seams are smooth and the metal does not splash (at the same time, vibrations of the electrode (the welder’s hand) and changes in length arcs practically do not cause a change in the welding current.If the current density increases and the burning point of the arc shifts to the ascending section, then the arc becomes unstable, “hard”, the metal spatters, the seams come out torn and uneven.

When welding with a semi-automatic MAG, the arc point should be located at the beginning of the ascending section of the current-voltage characteristic, with a high current density, and self-regulation of the welding process will occur.

Each type of welding must have a corresponding power source for the welding machine, be it an inverter or a transformer. For clarity, another graph,

which shows the external current-voltage characteristics of power sources for welding machines .

Curve 1 corresponds to a steeply falling current-voltage characteristic of the power source, which is almost ideal for manual welding on direct current MMA , curve 2 is a flat-sloping current-voltage characteristic, curve 3 is a rigid current-voltage characteristic that provides self-regulation when welding with thin MAG .

Conclusion : the power source for manual DC welding is designed and manufactured with a steeply falling current-voltage characteristic , which is absolutely not suitable for welding with a wire electrode in a semi-automatic mode . In relation to an inverter power source, the control unit must be redesigned and reconfigured, but if you are not very strong in electronics, then it is better not to mess with a well-established mechanism.

Good luck to you in life and on the road

Source: http://avtomastersam.ru/poluavtomat-iz-invertora-svoimi-rukami-vozmozhno-li-eto/

Converting an inverter into a semi-automatic welding machine - Welding Profi

A semi-automatic welding machine is a functional device that can be purchased ready-made or made from an inverter with your own hands.

It should be noted that making a semi-automatic device from an inverter device is not an easy task, but it can be solved if desired.

Those who set such a goal should thoroughly study the operating principle of a semi-automatic device, watch thematic photos and videos, and prepare all the necessary equipment and components.

Scheme of semi-automatic welding in a shielding gas environment

What is needed to convert an inverter into a semi-automatic machine?

To convert an inverter into a functional semi-automatic welding machine, you must find the following equipment and additional components:

• an inverter machine capable of generating a welding current of 150 A;
• a mechanism that will be responsible for feeding the welding wire;
• the main working element is the burner;
• a hose through which the welding wire will be fed;
• hose for supplying shielding gas to the welding area;
• a coil of welding wire (such a coil will need to undergo some modifications);
• an electronic unit that controls the operation of your homemade semi-automatic machine.

Electrical circuit of a homemade semi-automatic machine

Special attention should be devoted to redesigning the feeder, through which welding wire is supplied to the welding zone, moving along a flexible hose. In order for the weld to be high-quality, reliable and accurate, the wire feed speed through the flexible hose must correspond to the speed of its melting.

Since when welding using a semi-automatic machine, wire of different materials and different diameters can be used, its feed speed must be adjusted. It is precisely this function – regulation of the welding wire feed speed – that the feed mechanism of a semi-automatic device should perform.

Appearance of a homemade semi-automatic welder

Internal layout Wire reel Wire feeder (type 1)
Wire feeder (type 2) Attaching the welding hose to the feeder Design of a homemade torch

The most common wire diameters used in semi-automatic welding are 0.8; 1; 1.2 and 1.6 mm.

Before welding, the wire is wound onto special reels, which are attachments of semi-automatic devices, fixed to them using simple structural elements.

During the welding process, the wire is fed automatically, which significantly reduces the time spent on such a technological operation, simplifies it and makes it more efficient.

The main element of the electronic circuit of the semi-automatic control unit is a microcontroller, which is responsible for regulating and stabilizing the welding current. The parameters of the operating current and the possibility of their regulation depend on this element of the electronic circuit of the semi-automatic welding machine.

How to convert an inverter transformer

In order for the inverter to be used for a homemade semi-automatic device, its transformer must be subjected to some modifications. It’s not difficult to do this kind of alteration yourself, you just need to follow certain rules.

To bring the characteristics of the inverter transformer into line with those required for a semi-automatic device, you should wrap it with a copper strip on which a thermal paper winding is applied. It must be borne in mind that for these purposes you cannot use ordinary thick wire, which will become very hot.

Converted inverter transformer

The secondary winding of the inverter transformer also needs to be redone. To do this, you need to do the following: wind a winding consisting of three layers of sheet metal, each of which must be insulated with fluoroplastic tape; Solder the ends of the existing winding and the one you made yourself together, which will increase the conductivity of currents.

The design of the inverter used to include it in a semi-automatic welding machine must necessarily provide for the presence of a fan, which is necessary for effective cooling of the device.

Setting up an inverter used for semi-automatic welding

If you decide to make a semi-automatic welding machine with your own hands using an inverter, you must first turn off the power to this equipment. To prevent such a device from overheating, its rectifiers (input and output) and power switches should be placed on radiators.

Power diodes on additional radiators

After all of the above procedures have been completed, you can connect the power part of the device to its control unit and connect it to the electrical network.

When the network connection indicator lights up, an oscilloscope should be connected to the inverter outputs. Using this device, you need to find electrical pulses with a frequency of 40–50 kHz.

The time between the formation of such pulses should be 1.5 μs, which is regulated by changing the voltage value supplied to the device input.

Oscillogram of welding voltage and current: on the left with reverse polarity, on the right with direct polarity

It is also necessary to check that the pulses reflected on the oscilloscope screen are rectangular in shape, and their front is no more than 500 ns. If all the checked parameters correspond to the required values, then you can connect the inverter to the electrical network. The current coming from the output of the semi-automatic device must be at least 120 A.

If the current value is less, this may mean that a voltage is supplied to the equipment wires, the value of which does not exceed 100 V. If such a situation arises, you must do the following: test the equipment by changing the current strength (in this case, you must constantly monitor the voltage on the capacitor).

In addition, the temperature inside the device should be constantly monitored.

The current strength that flows to the welding torch in such a situation is controlled using an ammeter.

If the current strength when using a load rheostat does not meet the required parameters, then the resistance value of this device is selected empirically.

How to use a welding inverter

After starting the semi-automatic device that you assembled with your own hands, the inverter indicator should display a current value of 120 A. If everything is done correctly, then this will happen.

However, the inverter indicator may display a figure of eight. The reason for this is most often insufficient voltage in the welding wires.

It is better to immediately find the cause of such a malfunction and promptly eliminate it.

If everything is done correctly, the indicator will correctly show the strength of the welding current, which is adjusted using special buttons. The operating current adjustment interval provided by welding inverters is in the range of 20–160 A.

Approximate modes of semi-automatic welding of butt seams

How to monitor the correct operation of equipment

In order for the semi-automatic welding machine that you assembled with your own hands to serve you for a long time, it is better to constantly monitor the temperature conditions of the inverter.

To carry out such control, you need to press two buttons simultaneously, after which the temperature of the hottest inverter radiator will be displayed on the indicator.

The normal operating temperature is considered to be one whose value does not exceed 75 degrees Celsius.

If this value is exceeded, then, in addition to the information displayed on the indicator, the inverter will begin to emit an intermittent sound signal, which should be noted immediately.

In this case (as well as if the temperature sensor breaks or shorts), the electronic circuit of the device will automatically reduce the operating current to 20A, and a sound signal will be emitted until the equipment returns to normal.

In addition, a malfunction of self-made equipment may be indicated by an error code (Err) displayed on the inverter indicator.

Setting the welding mode on the Resanta inverter

In what cases is a semi-automatic welding machine used?

Practice shows that it is better to use a semi-automatic machine in cases where it is necessary to obtain precise and accurate connections of parts made of steel. With the help of such equipment, which, if desired, can be made by hand, welded joints of thin metal are made, which is very important when repairing the body of a vehicle.

Source: https://fgpip.ru/pajka/peredelka-invertora-v-svarochnyj-poluavtomat.html

Converting the inverter to a semi-automatic machine

A semi-automatic welding machine is a functional device that can be purchased ready-made or made from an inverter with your own hands. It should be noted that making a semi-automatic device from an inverter device is not an easy task, but it can be solved if desired. Those who set such a goal should thoroughly study the operating principle of a semi-automatic device, watch thematic photos and videos, and prepare all the necessary equipment and components.

Scheme of semi-automatic welding in a shielding gas environment

Semi-automatic from a conventional inverter

Inverters are widely used by home and garage craftsmen. However, welding with such a machine requires certain skills from the operator. The ability to “hold the arc” is required.

In addition, arc resistance is not a constant value, so the quality of the weld directly depends on the qualifications of the welder.

All these problems fade into the background if you work with a semi-automatic welding machine.

Design features and operating principle of the semi-automatic machine

A distinctive feature of this welder is that instead of replaceable electrodes, wire is continuously fed into the welding zone.

It provides constant contact and has less resistance compared to arc welding.

Due to this, a zone of molten metal is instantly formed at the point of contact with the workpiece. The liquid mass glues the surfaces together, forming a high-quality and durable seam.

Using a semi-automatic machine, any metals can be easily welded, including non-ferrous and stainless steel. You can master welding techniques on your own; there is no need to enroll in courses. The device is very easy to operate, even for a novice welder.

In addition to the electrical part - a high-power current source, the semi-automatic device has a mechanism for continuous supply of welding wire and a torch equipped with a nozzle for creating a gaseous environment.

They work with ordinary copper-plated wire in a protective inert gas environment (usually carbon dioxide). To do this, the cylinder with a reducer is connected to a special inlet fitting on the body of the semiautomatic device.

In addition, semi-automatic welding can be done in a self-protective environment, which is created using a special coating on the welding wire. In this case, no inert gas is used.

It is the ease of operation and versatility of the semi-automatic machine that makes the unit so popular among amateur welders.

Many kits implement a two-in-one function - a welding inverter and a semi-automatic machine in a common housing. An additional outlet is made from the inverter - a terminal for connecting the holder of replaceable electrodes.

The only serious drawback is that a high-quality semiautomatic device costs significantly more than a simple inverter. With similar characteristics, the cost differs by 3-4 times.

Therefore, home craftsmen strive, if possible, to convert the welding inverter into a semi-automatic device. We will tell you how to do this in the next article.

Do-it-yourself semi-automatic welding machine from an inverter

The basis of the future unit is a factory welding inverter with output current parameters of at least 150A. Some “Kulibins” recommend making changes to the inverter control module, since the current-voltage characteristic is falling normally, and for a semi-automatic device a different current-voltage characteristic curve is required.

To do this, you need to have a good understanding of how the device works. If the intervention is incorrect, the inverter will simply stop working. Therefore, the issue of modernizing the circuit is a separate conversation. Let's look at the mechanical part first.

To convert (more precisely, modify) the welding inverter into a semi-automatic device, we will need the following elements:

• welding wire feeder
• main tool – torch (gun)
• abrasion-resistant hose (internal) for feeding welding wire
• sealed hose for supplying inert gas to the welding zone
• reel (reel) with welding wire
• control unit for your semi-automatic machine.

The optimal solution would be to place the mechanical unit in a separate housing. A full-size box from a computer system unit works well. Moreover, the power supply is used for the wire feed mechanism.

Trying on the size of the wire spool. There should be enough space left for a standard power supply and a hose connector.

The roller feed mechanism is developed based on the existing engine. A good donor is a windshield wiper motor with a standard gearbox.

Source: https://MyTooling.ru/instrumenty/poluavtomat-iz-obychnogo-invertora

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

You can make a semi-automatic machine from an inverter yourself without much difficulty if you have the appropriate technical knowledge. To make a semi-automatic machine with your own hands, you will need to prepare a certain list of mechanisms, devices, tools and materials that are part of the unit.

The semi-automatic inverter includes an inverter and a welding torch.

Preparation for manufacturing and design features

Home craftsmen have developed various schemes for constructing semi-automatic machines from an inverter.

The most common device diagram involves the necessary list of tools and materials:

• welding inverter, which has the ability to deliver an operating current of about 150 A;
• a feeding mechanism that ensures the supply of electrode wire to the welding zone;
• burner;
• flexible hose;
• a working reel with electrode wire, which has changes in the device;
• device control unit.

The inverter should be about 150 A.

Particular attention should be paid to the feeding mechanism. By using this structural element, the electrode wire is supplied to the burner through a flexible hose. The ideal wire feed speed corresponds to the wire melting speed. The wire feed speed indicator, which is provided by the feed mechanism, has a significant impact on the work process and the quality of the weld using a semi-automatic welding machine.

When designing a semi-automatic machine, it is necessary to provide for the possibility of changing the speed of feeding the electrode wire into the welding zone. The ability to change the feed rate of electrode material allows you to work with consumables of different diameters and made of different materials. Most often, when operating semi-automatic welding machines, wire sizes of 0.8 mm, 1 mm, 1.2 mm and 1.6 mm are used. The wire is wound on special spools installed in the welding device.

If the wire feeding is carried out fully automatically, this significantly reduces the time required to carry out work on welding workpieces.

The semi-automatic control unit is equipped with a channel for adjusting and stabilizing the operating current. The operating current parameters are controlled by a microcontroller in pulse-width mode. The voltage on the capacitor largely depends on the pulse-width current parameter. The voltage on the latter directly affects the strength of the working welding current.

Selecting a transformer for the inverter and assembling the unit

Before independently designing a semi-automatic machine, you need to decide on the type and power of the welding transformer that you plan to install in the semi-automatic machine.

It should be remembered that when using a wire of a minimum size of 0.8 mm for the welding process, the operating welding current should be 160 A. The power of the welding transformer to produce such a current should be 3 kW.

When choosing a transformer, you should pay attention to the fact that a transformer with a toroidal core has less weight compared to other types of devices.

Transformer winding diagram.

When making a transformer, several subtleties need to be taken into account. The transformer needs to be wrapped with a copper strip with dimensions (40 mm - width and 30 mm - thickness). Before using the copper strip, it is first wrapped with thermal paper. You cannot use ordinary copper wire for winding, as it becomes very hot.

The secondary winding of the transformer is made of three layers of sheet metal. The layers of tin are insulated from each other using fluoroplastic tape. At the output, the ends are soldered together to increase conductivity. In the housing where the transformer is installed, a fan is mounted to provide airflow in order to increase the cooling of system components during operation of the device.

The current in the device can be adjusted in two ways: through the primary and secondary windings. Carrying out adjustment in the first way requires the use of a thyristor adjustment circuit. This method of regulation has certain disadvantages, which are eliminated by including a relay and some switching elements in the circuit.

When applying current regulation to the secondary winding, high ripple occurs, to reduce which a thyristor circuit is used. The use of switching circuits increases the weight of the structure and the cost of installation. For this reason, the use of current control through the primary winding is considered more acceptable.

To smooth out ripples, a smoothing inductor and a capacitor with a capacity of about 50,000 microfarads are built into the secondary winding circuit. This configuration of the device allows you to smooth out voltage ripples when choosing any current control scheme.

As a gearbox for feeding wire, you can use a gearbox from a VAZ windshield wiper.

Setting up a semi-automatic inverter

Device of a semi-automatic welding inverter.

When assembling a semi-automatic inverter with your own hands, it is necessary to ensure good cooling for the power switches, input and output rectifiers using radiators. A temperature sensor must also be installed in the housing. After installation of the power part of the device, it is connected to the device control unit.

The finished device can be connected to the network. After the indicator lights up, connect an oscilloscope to the device and check for correct operation. Bipolar pulses should have a frequency of 40-50 Hz, and the time between them is adjusted by changing the input voltage. The normal time interval between pulses should be 1.5 µs.

The pulses recorded by the oscilloscope must have rectangular edges with a duration of no more than 500 ns.

After checking the inverter, it is connected to the household electrical network. When connecting the device, the indicator should show 120 A. If this indicator is not reached, you need to check that the device is assembled correctly.

After testing the device at idle, the device is tested under load. For this purpose, it is necessary to include a load in the chain of welding wires in the form of a 0.5 Ohm rheostat, which is capable of withstanding a current of more than 60 A. With this load, the current is monitored using a voltmeter.

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After assembling the unit, its functionality is checked. To do this, click on the start button. Immediately after this, carbon dioxide begins to flow, after a few seconds the current is turned on, and the feeding of the electrode wire begins.

When the device is turned off, the supply of operating current and electrode wire first stops, and only after a few seconds the electrovalve is closed, providing the supply of carbon dioxide to the welding area.

As a valve to ensure the supply of carbon dioxide, you can use the water supply valve to the rear window of a VAZ car.

Rules for using a welding inverter and using the unit

After starting the inverter, the controller sets the current required for operation. If configured correctly, the electrical current at the output of the device is 120 A. Using the control unit, if necessary, the current can be changed in the range from 20 to 160 A.

When using the unit, you should monitor its heating temperature. The heating temperature should not exceed 75º C. To control it, a temperature sensor should be installed in the device. If the temperature rises above the set maximum, the device should be turned off and given time to cool down.

To improve cooling, the unit is equipped with several fans.

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Semi-automatic welding machine, made on the basis of an inverter, is used to carry out the procedure for precision welding of products made of various types of steel. In addition, the device is used for welding thin metal workpieces. The use of a semi-automatic machine is common when carrying out automotive body repair work.

After making semi-automatic welding from an inverter for the home, this unit becomes an indispensable device used in the household to perform a large number of different welding jobs.

Source: https://masterinstrumenta.ru/svarka/poluavtomat-iz-invertora-svoimi-rukami.html

Converting a welding inverter into a semi-automatic machine with your own hands - Metals, equipment, instructions

Any welder knows about the advantages of semi-automatic welding over manual electric welding. Due to their widespread use and low cost, MMA inverters are in the arsenal of many craftsmen. But with MIG welding it’s a different matter – these devices are more expensive. But there is a way out - you can make a semi-automatic device from an inverter with your own hands. If you delve into this issue, the matter turns out to be not so complicated.

Semi-automatic welding

There are fundamental differences between MMA and MIG welding. To operate a semi-automatic machine, you need carbon dioxide (or a mixture of carbon dioxide and argon) and electrode wire, which is fed to the welding site through a special hose. Those. The very principle of semi-automatic welding is more complicated, but it is universal and its use is justified. What is needed for the semi-automatic to work:

• wire feeder;
• burner;
• hose for supplying wire and gas to the heating pad;
• current source with constant voltage.
• And to turn an inverter welding machine into a semi-automatic machine, you will need a tool, time and desire.

Preparation

Manufacturing a semi-automatic welding machine at home begins with planning the work. There are two options for manufacturing MIG welding from an inverter:

In the first case, the cost of parts for the feeding device will be about 1000 rubles, excluding labor, of course. If a factory semi-automatic machine includes everything in one case, then a homemade one will consist of two parts:

1. Welding inverter.
2. Box with feeding mechanism and wire reel.

First, you need to decide on the body for the second part of the semi-automatic device. It is desirable that it be light and roomy. The feeding mechanism must be kept clean, otherwise the wire will feed jerkily; in addition, the reels must be changed periodically and the mechanism adjusted. Therefore, the drawer should be easy to close and open.

The ideal option is to use the old system unit:

1. neat appearance - it doesn’t really matter, but it’s much nicer when the insides of the homemade product don’t stick out and the semi-automatic machine made from an MMA inverter looks good;
2. light, closes;
3. the body is thin - it’s easy to make the necessary cutouts;
4. The gas valve and wire feed drive operate on 12 Volts. Therefore, a power supply from a computer will do, and it is already built into the case.

Now you need to estimate the size and location of future parts in the body. You can cut out approximate layouts from cardboard and check their relative position. After this, you can begin work.

The best option for electrode wire is a 5 kg coil. Its outer diameter is 200 mm, inner diameter is 50 mm. For the axis of rotation, you can use a PVC sewer pipe. Its outer diameter is 50 mm.

Burner

A homemade semi-automatic machine must be equipped with a burner. You can do it yourself, but it’s better to buy a ready-made kit, which includes:

1. Burner with a set of tips of different diameters.
2. Supply hose.
3. Euro connector.

A normal burner can be purchased for 2-3 thousand rubles. Moreover, the device is homemade, so you don’t have to chase expensive brands.

What to look for when choosing a kit:

• what welding current is the torch designed for;
• the length and rigidity of the hose - the main task of the hose is to ensure free flow of wire to the torch. If it is soft, any bend will slow down the movement;
• springs near the connector and burner - they prevent the hose from breaking.

Feeder

The electrode wire must be fed continuously and evenly - then the welding will be of high quality. The feed speed must be adjusted. There are three options for how to make the device:

If the third option is chosen, you will need:

• two bearings, guide roller, tension spring;
• motor for feeding wire - a motor from windshield wipers will do;
• metal plate for fastening the mechanism.

One pressure bearing - it must be adjustable, the second serves as a support for the roller. Manufacturing principle:

• holes are made on the plate for the motor shaft and for mounting bearings;
• the motor is fixed behind the plate;
• a guide roller is put on the shaft;
• bearings are fixed at the top and bottom;

It is best to place the bearings on metal strips - one edge is bolted to the main plate, and a spring with an adjusting bolt is connected to the other.

The completed mechanism is placed in the housing so that the rollers are located in line with the burner connector, i.e., so that the wire does not break. A rigid tube must be installed in front of the rollers to align the wire.

Implementation of the electrical part

For this you will need:

• two automotive relays;
• diode;
• PWM regulator for the engine;
• capacitor with transistor;
• idle solenoid valve - for supplying gas to the burner. Any VAZ model will do, for example from a V8;
• wires.

The wire and gas supply control circuit is quite simple and is implemented as follows:

• when you press the button on the burner, relay No. 1 and relay No. 2 are activated;
• relay No. 1 turns on the gas supply valve;
• relay No. 2 works in tandem with a capacitor and turns on the wire feed with a delay;
• wire pulling is done with an additional button, bypassing the gas supply relay;
• To remove self-induction from the solenoid valve, a diode is connected to it.
• It is necessary to provide for connecting the burner to the power cable from the inverter. To do this, next to the Euro connector, you can install a quick-release connector and connect it to the burner.

The semi-automatic device has the following operating sequence:

1. The gas supply is turned on.
2. The wire feed starts with a slight delay.

This sequence is necessary so that the wire immediately enters the protective environment. If you make a semi-automatic machine without delay, the wire will stick. To implement it, you will need a capacitor and a transistor through which the motor control relay is connected. Operating principle:

• voltage is applied to the capacitor;
• it is charging;
• current is supplied to the transistor;
• the relay turns on.

The capacitance of the capacitor must be selected so that the delay is approximately 0.5 seconds - this is enough to fill the weld pool.

After assembly, the mechanism must be tested, and the manufacturing process can be seen on video.

Inverter conversion

To make a semi-automatic machine from a conventional inverter with your own hands, you will have to slightly alter its electrical part. If you connect an MMA inverter to the assembled case, you will be able to cook. But at the same time, the quality of welding will be far from that of a factory semi-automatic machine.

It's all about the current-voltage characteristics - current-voltage characteristics. The electric arc inverter produces a falling characteristic - the output voltage floats. And for the correct operation of a semi-automatic device, a strict characteristic is required - the device maintains a constant voltage at the output.

Therefore, in order to use your inverter as a current source, you need to change its current-voltage characteristic (volt-ampere characteristic). For this you will need:

• toggle switch, wires;
• variable resistor and two constant;

Getting a hard characteristic on an inverter is quite simple. To do this, you need to place a voltage divider in front of the shunt that controls the welding current. Fixed resistors are used for the divider.

Now you can get the required millivolts, which will be proportional to the output voltage, not the current. There is only one drawback to this scheme - the arc is too rigid.

To soften it, you can use a variable resistor, which is connected to the divider and the output of the shunt.

The advantage of this approach is that the arc stiffness can be adjusted - this setting is only available in professional semi-automatic machines. And the toggle switch switches the inverter between MMA and MIG modes.

Thus, converting an MMA inverter into a semi-automatic device, although not an easy task, is quite feasible. The result is a device that is not inferior to the factory ones in its characteristics. But at the same time it is much cheaper. The cost of such an alteration is 4-5 thousand rubles.

Source: https://spb-metalloobrabotka.com/peredelka-svarochnogo-invertora-v-poluavtomat-svoimi-rukami/

Design and operation of a semi-automatic device

Welding of metal products can be done in different ways, but in all cases an electric arc is used. Among them, semi-automatic machines are very popular, capable of joining any metals.

In its work, a semi-automatic welding inverter uses protective gases that prevent the occurrence of chemical reactions in the molten medium. In some models, carbon dioxide is used for these purposes, but in most devices various inert gases are used - argon, helium and others. This welding is known under the abbreviated name MIG or MIG - Metal Inert Gas welding.

Main parts and components of semi-automatic welding:

• An inverter or transformer that acts as a current generator.
• Gas cylinder equipped with a reducer.
• Electrical cables and hoses of the required cross-section and size.
• Gas burner coupled with a welding wire feed mechanism.
• A device that feeds wire to the welding site.

Welding wire is made from different metals and is essentially a consumable electrode. It is pre-wound on a drum and then automatically fed to the point of contact between the part and the burner.

The speed of the wire depends on its diameter and the magnitude of the welding current. When the handle is pressed, an electric arc occurs, at the same time the wire is fed to the welding seam, and the gas, under pressure, blows through the bath.

Atmospheric air can no longer enter the hot metal and oxidize it.

In this case, the function of the gas is similar to the protective coating of a standard electrode, only the combustion of the material covering the rod is not required to form the protective layer.

All welding components - inverter, drum, gas cylinder - create some cumbersomeness of the system, negatively affecting mobility. However, this disadvantage is offset by the significant advantages of semi-automatic machines.

During operation, there is no release of toxic fumes, the electric arc is easily ignited and maintained, the wire is consumed in a minimal amount, and even very thin metal sheets can be joined.

Carbon dioxide welding works on the same principle, but the cylinder contains cheaper carbon dioxide. The set of functions is almost the same, with the exception of some restrictions regarding the products being welded. Professional semi-automatic machines can operate in two modes – with carbon dioxide and with inert gases. Current adjustment is carried out in a wide range, and the wire diameter can be any, in the range of 0.5-4.0 mm.

Mechanical part for wire feeding

Without a wire feeding mechanism, a semi-automatic welding machine simply will not work. Typically, a separate box is used to house the device. The case from a computer system unit is best suited.

Work begins with determining the diameter of the future coil on which the wire will be wound. If the part is not yet available, you can make a paper template and insert it into place. There should be free space around, since other components and parts will be placed nearby.

Most often, the pulling mechanism is made from a car windshield wiper. A special frame is developed for it to hold the pressure rollers. A drawing of the entire structure is applied to cardboard or thick paper in full size. In order not to bother with making the burner and hose, as well as with the connection connector, it is recommended to purchase them ready-made in one set at a very affordable price.

The feeder should be installed in such a way that the connection connector is located in a convenient place. Uniform movement of the wire is ensured by precise fastening of all elements opposite each other.

The connection connector contains an input fitting, for which a special hole is provided in the housing. The rollers of the broaching mechanism are also centered under it. The guides are bearings with a suitable diameter, in which a small groove needs to be machined on a lathe for the wire.

The mechanism is placed inside a case made of durable plastic, textolite or thick plywood. All components are attached to a common base.

The primary wire guide is made from a bolt drilled along its entire length. A cambric is installed at the inlet of the fitting, spring-loaded to impart rigidity. In addition, rods with fixed rollers are reinforced with springs. The compression force is regulated by a bolt located at the bottom and connected to the spring.

If, for a number of reasons, it is impossible to make a broaching mechanism with your own hands, you can buy it ready-made. The devices are powered by 12 and 24 volts. The computer case has a power supply designed for 12 V, so the system should be selected according to this parameter.

Control electronics

When the semi-automatic machine from the inverter is assembled, and all the parts and components are placed inside the housing, you can proceed to creating a control system for the mechanical part.

The quality of the weld seam largely depends on the wire feed speed, which must remain constant throughout the entire welding process. This parameter is provided by the motor from the car windshield wiper. To change the rotation speed, you need to make the semi-automatic device connected to a PWM controller. This device has a digital display mounted on the front panel of the housing.

The gas valve is controlled by a separate relay, which is used to start the engine. Activation of all elements occurs after pressing the start button installed on the burner handle. Gas should arrive at the welding site before the wire is fed, with some advance, by about 2-3 seconds. If this condition is not met, the arc will ignite in the open air and not in a protective gas environment. Because of this, the wire may melt prematurely.

As the basis of the delay relay, you can take the 815th transistor and a capacitor with a capacity of 200-2500 μF, which provides a two-second pause. If you have a 12 V power supply from a computer, you can use a car relay instead of the proposed circuit.

The shut-off solenoid valve is located in places where it will not affect the functions of moving parts. You can buy a finished product or use the air valve of a GAZ-24 car. Thanks to this component, shielding gas is automatically supplied to the torch. It turns on only after pressing the start button, thereby eliminating the overconsumption of expensive gas.

After checking the functionality of the circuit, all components are also placed inside the housing. However, the efficient operation of a semiautomatic device cannot be fully ensured by the current-voltage characteristics of the inverter used. In order for the system to work fully, minor changes need to be made to the circuit.

Transformer conversion

Due to its characteristics, the inverter cannot be directly used in semi-automatic welding equipment. It is necessary to make certain changes to the design of the transformer. This procedure is quite within the capabilities of a home handyman, provided that the procedure is followed. This is a mandatory action when converting an inverter into a semi-automatic machine.

In order for the parameters of the transformer located in the inverter to meet the requirements for a semi-automatic machine, it is necessary to perform the following operations:

• A copper strip pre-wrapped with thermal paper is wound onto the transformer. In this case, it is not allowed to use ordinary thick wire, which is not capable of withstanding increased loads. It will get very hot during operation and will burn out very quickly.
• The secondary winding is also redesigned. To do this, winding is done with three-layer tin. Each layer is isolated from each other with fluoroplastic tape. The new winding is connected to the existing winding by soldering, thereby ensuring good current conductivity.

The resulting system needs cooling, so a fan must be included in the circuit.

Setting up a semi-automatic machine and preparing for work

After assembling the broaching mechanism, the control unit and the transformer itself, the device should be properly configured and prepared for operation. First of all, the power part is connected to the control unit and connected to the network.

After the voltage indicator lights up, an oscilloscope is connected to the output terminals. It is necessary to detect electrical pulses with a frequency in the range of 40-50 kHz.

The time interval between their formations is 1.5 μs, and this value is adjusted by changing the input voltage.

Next, the shape of the pulses displayed on the screen is checked. It should be rectangular, with a front size of no higher than 500 ns. If the check does not reveal any deviations, then the inverter is connected to the network. The current strength at the output of the semi-automatic device is not lower than 120 A. If the value is lower, you should check the voltage, which is most likely no more than 100 volts. It is possible to achieve the desired results by adjusting the current while simultaneously controlling the temperature inside the device.

After routine testing, the semi-automatic machine is tested under load. For this purpose, the welding wires are connected to a rheostat with a resistance of at least 0.5 Ohm, capable of withstanding a current of 60 A. The current supplied to the welding torch is checked with an ammeter. If the current strength does not meet the established standards, the resistance should be changed.

After all the manipulations are completed and the settings are completed, the inverter indicator should show a current of 120 amperes on the display. This number is always displayed if all actions have been performed correctly. In some cases, figure eights may appear, indicating a lack of voltage in the welding wires. The required value is set by adjusting the operating current, which can be performed in the range from 20 to 160 A.

Source: https://electric-220.ru/news/poluavtomat_iz_invertora_svoimi_rukami/2019-05-21-1692

Converting an inverter into a semi-automatic welding machine

Among beginners and professional welders, an inverter-type semi-automatic welding machine is the most popular device. For the former, it provides ease in acquiring welding skills; for the latter, it provides productivity and a large range of additional settings.

Semi-automatic welding equipment can be useful for almost any welder, but has a fairly high cost. If you have manual arc welding, you can convert it into a semi-automatic inverter type.

Difference from manual cooking

The semi-automatic welding machine is initially designed to work with filler wire in a protective gas environment (inert or active). Its difference from a conventional manual arc welding machine is the presence of a wire feed mechanism, a gas cylinder, a special torch and a gas and additive control unit.

The power source itself in the form of an inverter is no different. If the feed mechanism is built into the inverter housing, there is an additional wire connector.

Therefore, many owners of manual arc welding machines eventually have a desire to expand their capabilities and make a homemade semi-automatic machine. It can be implemented very easily. There are several implementation options; which one to choose depends on the availability of funds, time and desire.

Multifunction devices

Some manufacturers of manual arc welding inverters, taking into account the wishes of customers, have provided the required additional connectors. They help convert the device into a semi-automatic device as quickly as possible.

Some models of “Source” type inverter devices on the rear panel have a key for switching the operating mode from MMA to MIG and a connector for controlling on/off the inverter. Welding wire feeders are usually equipped with a 3 m long Euro hose with a torch at one end and a connector at the other.

The connector allows you to supply welding wire and shielding gas; in addition, a cable passes through it to supply control signals to the electric motor for drawing the additive and connecting the gas.

There is a special cable for connection to the inverter device. It must be connected to the connector through which the welding current from the inverter was supplied to the electric holder. Now, in a semi-automatic mode, it will go to the MIG torch.

The second cable powers the feed mechanism from the inverter, if it has an appropriate connector, or from another low-power 12 V DC source.

Before work, the required gas flow rate is set on the gas cylinder, and the feed rate of the additive is set on the feed mechanism. The inverter sets the welding current, the value of which depends on the thickness of the metal being welded.

Then start welding. As you can see, turning manual arc welding into semi-automatic does not require any modifications; it is enough to purchase the missing equipment. The only drawback is that the inverter will come with a pulling device attachment.

Pulling device

In a more complex case, the manufacture of a semi-automatic machine involves reworking the arc welding inverter and creating a broaching device from scrap materials. If you had to repair an inverter device, then you can safely implement the second option.

A system unit is ideal as a housing for a drawing device for an inverter-type semi-automatic device. It is quite easy to open, yet spacious and durable.

This will allow you to simply adjust the pressure of the rollers and install the spool of wire. The advantage of the system unit is that it is easy to make holes in the right places, and there is a built-in 12-volt power supply. It is needed to power the additive broach drive and the gas valve.

For the necessary fasteners, it is necessary to make mock-ups of the built-in components from scrap materials and try them on inside the box. After making sure that the selected layouts are correct, you can begin manufacturing the fasteners.

You can buy a reel for a semi-automatic machine ready-made or make it yourself. It is very simple to produce. The diameter of the cheeks should be 200 mm, and the cylinder on which the wire will be wound should have a diameter of 50 mm, so that a plastic pipe with the same rating can be used as an axis.

The feed mechanism will require two pressure rollers and one guide roller and a spring. An electric motor from the wipers can be used as a broaching motor. As a base on which the parts will be attached, you need to use a three-millimeter metal sheet.

Holes are drilled in the plate in the right places for attaching the rollers and the electric motor shaft of the future semi-automatic device. Since one roller is a pressure roller, the hole for it is drilled in an oblong shape.

A pressure spring will press on it from above, the force of which is adjusted through a screw. The roller and bearings are mounted on one side of the plate, and the motor on the other. A feed roller is mounted on the motor shaft.

The resulting device is installed inside the system unit so that the alignment of the rollers and the axis of the MIG torch connector are in the same plane. This will prevent the wire from creasing when pulling. To straighten the additive during unwinding, a tube is installed in front of the rollers.

Control node

To supply gas and additives to the semi-automatic welding machine you will need:

• 2 relays;
• diode;
• PWM regulator;
• capacitance with transistor and resistance;
• solenoid valve;
• wires.

The valve is required to allow gas to enter the welding zone. All components can be purchased at the used parts sale.

The control circuits in an inverter-type semi-automatic device may be different, but their essence is simple and is as follows.

When you press the button on the burner, both relays switch. The first supplies voltage to the valve that opens the gas supply.

The second relay supplies power to the wire feed motor. But its activation occurs a little later due to the low-pass filter in the form of an RC chain formed by a capacitor and a resistor.

Sometimes it is necessary to draw wire without gas supply. For this case, an additional button is provided that provides broaching, bypassing the gas relay.

Self-inductance from the valve is removed if a diode is connected. To power the MIG torch from the inverter, you need to install an additional one next to the Euro connector, through which the current will flow.

When you turn on the button on the burner, gas begins to flow, after a while the additive is supplied. The delay time is regulated by selected capacitance and resistor values. A pause in an inverter-type semi-automatic machine is necessary to protect the weld pool from exposure to atmospheric air with gas.

When the button is turned on, voltage is supplied to the capacitor. It gradually charges, and when a certain value is reached, the transistor opens, which causes the relay to turn on.

Inverter

The manual arc welding inverter also needs to be rebuilt. Although it can be used without modifications, the quality of welding will then be lower than that of factory semi-automatic welding machines. It's all about the current-voltage characteristics. The difference is minor, but it has an impact.

To eliminate these differences, you will need a toggle switch, three resistances, one of which is variable.

To adjust the characteristic, it is necessary to install a divider in front of the shunt, which controls the current. By changing the parameters of the divider, an adjustment will occur. The toggle switch is needed to switch the inverter operating mode from manual arc to MIG.

As a result of modification of the inverter and self-manufacturing of the filler wire drawing device, semi-automatic welding equipment with good parameters is obtained. At the same time, you save money and get a lot of pleasure from the fact that you did everything yourself.

If you have to do professional welding, then it is better to purchase a ready-made semi-automatic machine. Today, the choice of these devices is wide, and it is quite possible to choose a budget model of acceptable quality.

Source: https://svaring.com/welding/apparaty/svarochnyj-poluavtomat-invertornogo-tipa