Plasma cutter: principle of operation, device, instructions for use
What is a plasma cutter and for what how does it work? If we talk about this tool, then it should be noted right away that this is the device that welders use, and not all of them. For one-time use, such a tool is never used anywhere. For this reason, there are tools with which it is possible to carry out cutting operations, and at the same time not resort to using an expensive option, namely a grinder. But if the requirements for the volume and speed of the process are stricter, then you cannot do without using a plasma cutter.
It is for this reason that it is used in the mechanical engineering industry, in the manufacture of large structures from metal, for cutting pipes and everything else.
A lot when choosing a plasma cutter will depend on the area in which you plan to use it. The fact is that the design features of all types are very different from each other - each device has its own type of arc ignition, as well as the power of the cooling system.
Such common ones are saturated with oxygen.
There is another classification that helps to divide and buy a plasma cutter by the type of equipment that is used for work.
By the type of contact, the devices can be divided into two groups - contactless and contact. From the name it is already easy to understand what methods of using a plasma cutter are.
In the first case, the device does not require contact with the metal being processed, and the thickness of the workpiece can be any, while in the second case, contact with the metal is required, and its thickness must be at least 1.8 cm.
Another category is the type of use and the ability to be powered by electrical energy. in this case, there is a household cutter, which operates from a network with alternating current and a standard voltage of 220 V, and an industrial cutter, which can only be connected to a three-phase supply network with a voltage of 380 V.
Please note that even those torches that have a minimum power will be from 4 kW.
For this reason, when connecting it to a household power supply, first make sure that it can accurately withstand such a load.
This load is not the only one, since the plasma cutting system uses cooling, and for this, a compressor is included with the standard equipment, which will also work from the mains. Consider its power when connecting to home power.
The name itself is already clear that the metal cutting process is carried out thanks to plasma, the latter being an ionized gas with a high electrical conductivity. The higher the gas temperature, the higher the conductivity will be, and the cutting force will increase significantly.
An air-plasma arc is also used for the metal cutting process. Please note that in this case, the current will already have a direct effect on the metal surface.
It turns out that the principle of the device is as follows:
Manual plasma cutter consists of:
It will not be superfluous to understand in order to understand the design features of the cutter. Inside the device there is an installed electrode, which is made of a rare metal such as hafnium, beryllium, zirconium, and others.
Why these metals? The fact is that when heated, refractory types of oxides are formed on the surface of this electrode. It is a kind of protection of the electrode, which will ensure the integrity of the material, that is, not destroy. Most often, hafnium electrodes are installed in plasma cutters, because this metal is not toxic and radioactive, like, for example, beryllium.
The nozzle plays an important role in the design - it is through it that the plasma enters the cutting. It is from him that the main parameters of the device will depend, or rather, on the thickness and length of the nozzle.
T diameter will depend on the power of the plasma flow, and hence the shear speed and width of the cut groove. Of course, the cooling rate will also depend on this. Most often, a nozzle is installed on the cutters, the diameter of which is 0.3 cm.The length will directly affect the quality of the cut - the longer, the better.
Note that a very long nozzle will fail quickly.
So, when you press the ignition button, the power source is automatically turned on, and high-frequency current enters the cutter. Because of this, a pilot arc appears between the electrode and the nozzle tip. The arc temperature ranges from +6,000 to +8,000 degrees.You should pay attention to the fact that the arc between the cut metal and the electrode does not appear immediately, it takes time.
After that, air from the compressor (compressed) begins to flow into the torch chamber. The air begins to heat up when passing through the chamber in which the pilot arc is located, and it becomes 100 times larger. In addition, it begins to ionize, in fact, turning into a conductive medium, although air itself is a dielectric.
A nozzle that is tapered to 0.3 cm creates a plasma stream that exits the torch at high speed (2 to 3 meters per second).
The temperature of the air, which has become ionized, reaches up to +30,000 degrees. With this temperature, air conductivity becomes the same as the conductivity of metal. As soon as the plasma hits the surface to be treated, the pilot arc is turned off, but the working arc is turned on instead. Melting of the metal workpiece is carried out at the cut-off point, from where the liquid metal is blown away by air, which enters the cut-off zone. This is the cutting diagram.
People who have worked with a plasma cutter will note that the greater the current flowing to the electrode, the faster the process will be ... But there are also some conditions that will be affected by other parameters of the equipment. This includes the thickness of the cut and the type of metal.
It will depend on such parameters which equipment to choose for work, namely, such of parameters as current strength. To cut a copper sheet with a thickness of 0.2 cm, you will need a plasma cutter with an amperage of 12 A.
Please note, we advise you to buy equipment that will have a stock current strength. Usually, the specified parameters when buying are maximum, which means that they will work for a short time.
Advantages and disadvantages
Before making a choice and deciding whether to buy a plasma cutter or not, you should find out about all the negative and positive aspects of the equipment. So, for example, at home, this device is interchangeable with a grinder.
So, the advantages are as follows:
The result is a smooth, thin and even cut.
And, nevertheless, the plasma cutter as a device is quite in demand. Manual types are often used, but only in small enterprises where large volumes of cutting need to be performed and strict requirements are imposed on the quality of the cut.
Posted By: Work Style |10, Nov 2020
Posted By: Work Style |10, Nov 2020
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