How Does A Plasma Cutter Work?
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    Default How Does A Plasma Cutter Work?

    Plasma cutter, as an important cutting style, is widely used in different kinds of industries. However, few people know exactly how does a plasma cutter work, which, undoubtedly, affects the proper use of plasma cutter machine.

    One basic question will have to be explained if we want to know well of plasma cutter: what is plasma? Plasma can be regarded as the forth state of matter after the state of solid, liquid and gas. Generally, matter changes from one state to the other by transformation of energy, Take water for example, it will become liquid when a certain amount of heat is applied to ice, which is and obvious state change from solid to liquid. When headed continuously, the heat level will increase and it will become steam, which is the gas state. if the heat levels increase more, the gas that make up the steam will become ionized and electrically conductive, what is so called plasma.
    how-does-plasma-cutter-work-300x245.jpg
    when some gas, such as oxygen, nitrogen, argon or even air, is forced through a small nozzle orifice inside the torch, plasma arc formation begins, the electric arc which is generated from the external power supply is then introduced to this high pressured gas flow, resulting in what is commonly referred to as a “plasma jet”. The plasma jet immediately reaches temperatures up to 22000° C, quickly piercing through the work piece and blowing away the molten material.

    The Plasma cutter uses the heat generated by arcing between the material and electrode inside the torch to partially melt or evaporate the metal, and removes the molten metal by high-speed plasma momentum to form a cutting slit.

    Working with different gases, plasma cutter can cut a variety of metal materials which are difficult to cut by oxygen, especially non-ferrous metals, such as stainless steel, aluminum, copper, titanium, nickel,etc. main advantage of plasma cutter is the high cutting speed for some metal with of small thickness, especially when cutting ordinary carbon steel sheets, the speed can reach 5-6 times of the oxygen cutting, the cutting surface is smooth with small heat deformation and the heat affected zone.
    gantry-cnc-plasma-cutter-machine-300x205.jpg

    Plasma cutter is thus widely used in different industries and fields, including automobiles, locomotives, pressure vessels, chemical machinery, nuclear industry, general machinery, engineering machinery, steel structures, ships, etc.

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    spam.

    moderator, please lock or delete this.

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    Plasma cutter uses the heat generated by arcing between the material and electrode inside the torch to partially melt or evaporate the metal, and removes the molten metal by high-speed plasma momentum to form a cutting slit.

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    Quote Originally Posted by stargrit View Post
    Plasma cutter uses the heat generated by arcing between the material and electrode inside the torch to partially melt or evaporate the metal, and removes the molten metal by high-speed plasma momentum to form a cutting slit.
    You need to learn how to spot a spammer, and not just read the title.

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    I know this is spam, but every explanation of plasma systems I've seen is incomplete and I just want to add in the last bit of information.

    Air (or in fancy cases a different shielding gas) is forced around the electrode in a spiral pattern. As the arc and shielding gas are constricted through the nozzle, the shielding gas swirls faster and faster. This swirling acts as a centrifuge forcing the colder, denser gas against the nozzle walls which in turn keeps the hot, less dense plasma centered. Since the plasma is constricted radially as it continues to heat up from the arc it can only expand straight downwards. Upon exiting the nozzle the swirling shielding gas flings off mostly sideways and the hot plasma continues straight down through the metal. This is why plasma cutters can cut thick steel but don't cut through their nozzles.

    If you tried to just shove a regular arc through a nozzle you would have a melty mess.


    Fun fact: fire can be plasma, but usually isn't. A typical orange or yellow flame is just gas that's so hot it's glowing. A flame becomes purple or blue when it becomes so hot that the atoms cannot hold on to their electrons, and is therefore a plasma.*

    *Exceptions apply

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    Quote Originally Posted by Strostkovy View Post
    Fun fact: fire can be plasma, but usually isn't. A typical orange or yellow flame is just gas that's so hot it's glowing. A flame becomes purple or blue when it becomes so hot that the atoms cannot hold on to their electrons, and is therefore a plasma.*
    *Exceptions apply
    So if I apply EMF to a natural gas-air burner adjusted to blue flame I may be able to measure some current flow through the flame? Interesting, I'll try that.
    Come to think if it, in electronics, I have heard of "flame triodes" something like a vacuum tube (valve) triode, but not in a vacuum, using a flame passing through a control grid, and a plate near the top of the flame. Electrode near the base of the flame acting as a cathode. No practical use, just an interesting experiment.

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    Really? I pull the trigger and something is supposed to happen. Some noise and some sparks? After that I am supposed to move my hand around. Hand with the sparking thingy. Maybe I need to update WTF that heavy black box thing is used for. Keeps a cart stable for the most part.

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    Orange or yellow flame is actually glowing soot particles.

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    Quote Originally Posted by Strostkovy View Post
    Air (or in fancy cases a different shielding gas) is forced around the electrode in a spiral pattern. As the arc and shielding gas are constricted through the nozzle, the shielding gas swirls faster and faster. This swirling acts as a centrifuge forcing the colder, denser gas against the nozzle walls which in turn keeps the hot, less dense plasma centered. Since the plasma is constricted radially as it continues to heat up from the arc it can only expand straight downwards. Upon exiting the nozzle the swirling shielding gas flings off mostly sideways and the hot plasma continues straight down through the metal. This is why plasma cutters can cut thick steel but don't cut through their nozzles.

    If you tried to just shove a regular arc through a nozzle you would have a melty mess.

    Really ?

    So how does the qty (3) plasma cutters work that I own that have straight electrodes ?

    No swirling going on.

    The only swirling going on is the crap you are spewing.

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    Quote Originally Posted by digger doug View Post
    Really ?

    So how does the qty (3) plasma cutters work that I own that have straight electrodes ?

    No swirling going on.

    The only swirling going on is the crap you are spewing.
    Dude really...its magic

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    Quote Originally Posted by plastikdreams View Post
    Dude really...its magic
    Dood....How many plasma cutters have you fixed, and retro-fitted new, different torches to ?

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    doug, all my plasma cutters have straight electrodes, too- but cone shaped tips, where the swirlies go on. That would include, Miller, Thermal Dynamics, and now Victor torches. I have gone thru my share of torches since my first one in 92, and they all use the swirly technology that strostkovy talks about. Methinks yours do too. Optimizing Automated Plasma Cut Quality

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    Quote Originally Posted by digger doug View Post
    Dood....How many plasma cutters have you fixed, and retro-fitted new, different torches to ?
    That would be....zeeeeeeeero

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    the swirl ring does not have to be a threaded electrode like the hypertherm xp stuff. millers have the washer looking thing, big plasmas have the volcanic ash part with tiny holes that goes over the straight electrode. the swirls scours on a electrode can be seen if replaced before it is toasted, the nozzle will show them too on the inside. It is also why you replace electrode and nozzle as a pair, to match the erosion on each.

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    Quote Originally Posted by digger doug View Post
    Really ?

    So how does the qty (3) plasma cutters work that I own that have straight electrodes ?

    No swirling going on.

    The only swirling going on is the crap you are spewing.
    Remove everything in the air path in the torch except for the nozzle and electrode. You will have a melty mess.

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    Quote Originally Posted by Strostkovy View Post
    Air (or in fancy cases a different shielding gas) is forced around the electrode in a spiral pattern. As the arc and shielding gas are constricted through the nozzle, the shielding gas swirls faster and faster. This swirling acts as a centrifuge forcing the colder, denser gas against the nozzle walls which in turn keeps the hot, less dense plasma centered. Since the plasma is constricted radially as it continues to heat up from the arc it can only expand straight downwards. Upon exiting the nozzle the swirling shielding gas flings off mostly sideways and the hot plasma continues straight down through the metal. This is why plasma cutters can cut thick steel but don't cut through their nozzles.

    If you tried to just shove a regular arc through a nozzle you would have a melty mess.
    Strostkovy,

    thanks for that information.

    I've been involved with DIY plasma for quite a few years now, built my own CNC table, and have recently designed/built my own THC so I'm not locked in to 3rd party black box systems. I've been haunting plasma related forums for years but have never heard the above information, or any other explanation of how the plasma jet heat does not melt the nozzle. I believe what you said is true simply because it makes so much sense. Whenever a pierce is done the resulting hole is much bigger that the plasma nozzle, and if the pierce time is too long the diameter of the hole gets bigger. To me, that goes to show that simply the surrounding heat from the plasma jet is enough to melt steel. The arc starts at the hafnium insert in the electrode which is INSIDE the nozzle, so why doesn't the arc melt the nozzle hole as it does the material ??? Not only that but the amount of cutting/piercing that one single nozzle can do, it would not be possible is the heat from the plasma jet made it to the nozzle hole wall.

    It makes perfect sense what you explained.

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    I found this idea of a plasma stream mysterious until I remembered my aircraft maintenance training. Ignition systems on large radials was often pressurized so that the air in the distributor and high tension system was more dense. Operating at high altitudes is a problem unless the system is pressurized. Electric arcs like to travel in a less dense atmosphere so logically a plasma stream would take the path of least resistance which would be the center of the vortex created in the nozzle of your plasma cutter.
    Good to know that the cut is always better on one side than the other due to the direction of the vortex.


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