principles of plasma cutting

7/29/2019 Principles of Plasma Cutting

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Principles of plasma cutting

What is plasma cutting?

This is a cutting system utilizing heat generated by arc discharge between the cutting object

material and the electrode inside the torch. Arc discharge heat forms working gas into the

plasma state of high temperature; the plasma jet of high temperature and high-speed is blown

out from the nozzle; and the cutting object material is fused to be cut.

What is plasma?

Heating a gas to a high temperature makes kinetic energy of its molecule or atom large, such particles vigorously collide each other; electron

inside the atom is taken away resulting in positively charged ions and negatively charged electrons being mixed up; as a whole, each charge

offsets one another, producing a state of electrically neutral, which state is called plasma. This plasma appears when a gas is heated to 5 to 7

thousand degrees or higher at the atmospheric pressure.

What is thermal pinch effect?

A state where kinetic energy of positively charged ions and that of negatively charged electrons are equal is called thermal equilibrium plasma.

Under such a plasma state, lower the temperature gets, lower the easiness in current flow (electric conductivity) gets. In arc discharge, a current

is flown at the plasma part formed between electrodes to generate resistant heat there to hold a high temperature. If the plasma at the

circumference of the discharge part is cooled, electricity gets hard to flow there, and the current concentrates into the core part. This

phenomenon is called thermal pinch. In the plasma torch, an intensively cooled nozzle is used to squeeze the plasma generation into a narrow

range to draw out this effect.

What is Plasma Cutting?

Plasma cutting was accidentally discovered by an inventor who was trying to develop a better welding process.Though the technology is still young today, plasma cutting is quickly changing the world as we know it.

Plasma cutting is by far the simplest and most economical way to cut a variety of metal shapes accurately. Plasmacutters can cut much finer, faster, and more automatically than oxy-acetylene torches. Because of their effectiveness,plasma cutters - especially CNC plasma cutters (see below) - threaten to obsolete a large number of conventionalmetalworking tools.

How a Plasma Cutter worksBasic plasma cutters use electricity to superheat air into plasma, which is then blown through the metal to be cut.Plasma cutters are extremely simple and require only a compressed air supply and an AC power outlet to operate.

A complete plasma cutter consists of a power supply, a ground clamp, and a hand torch. The main function of thepower supply is to convert the AC line voltage into a user-adjustable regulated (continuous) DC current. The handtorch contains a trigger for controlling the cutting, and a nozzle through which the compressed air blows. An electrode

is also mounted inside the hand torch, behind the nozzle.

Operation

1. Initially, the electrode is in contact with (touches) the nozzle.


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2. When the trigger is squeezed, DC current flows through this contact.3. Next, compressed air starts trying to force its way through the joint and out the nozzle.4. Air moves the electrode back and establishes a fixed gap between it and the tip. (The power supply

automatically increases the voltage in order to maintain a constant current through the joint - a current that isnow going through the air gap and turning the air into plasma.)

5. Finally, the regulated DC current is switched so that it no longer flows through the nozzle but instead flowsbetween the electrode and the work piece. This current and airflow continues until cutting is halted.

Notes

Plasma cutters are only useful for cutting metal. Non-conductive materials like wood and plastic prevent the plasmacutter from doing step 5 above.

The above steps describe the operation of a contact-type arc starting plasma torch (the lastest technology). Oldplasma torch designs use high voltage sparks to bridge the gap between a fixed electrode and tip when starting thearc. These old designs are not recommended for several reasons (see link below).

The only parts of the plasma cutter needing frequent replacement are the nozzle and the electrode. For this reason,these parts are called "consumables."

Plasma cutting is a process that is used to cutsteeland othermetalsof different thicknesses (or sometimes other

materials) using aplasma torch. In this process, an inert gas (in some units, compressed air) is blown at high speed

out of a nozzle; at the same time an electrical arc is formed through that gas from the nozzle to the surface being cut,

turning some of that gas toplasma.[1]

The plasma is sufficiently hot to melt the metal being cut and moves sufficiently

fast to blow molten metal away from the cut.

ARTOTC ELECTRO-OPTICAL TRACE CUTTING MACHINE

ArtOTC Electro-Optical Trace Cutting Machine is a unique and efficient system for automatic gas cutting

equipment, allowing complex shapes to be cut in a very simple manner. The machine is very affordable, easy to

install and simple to operate, and designed to be reliable and convenient to service. The machine uses theLINATROL photoelectric tracing system for motion control and to activate gas cutting. The system follows a

pattern or shape outline, and completes 1:1 work piece cutting. The ArtOTC is the perfect choice for low volume

cutting and factory maintenance applications.
https://en.wikipedia.org/wiki/Steelhttps://en.wikipedia.org/wiki/Steelhttps://en.wikipedia.org/wiki/Steelhttps://en.wikipedia.org/wiki/Metalhttps://en.wikipedia.org/wiki/Metalhttps://en.wikipedia.org/wiki/Metalhttps://en.wikipedia.org/wiki/Plasma_torchhttps://en.wikipedia.org/wiki/Plasma_torchhttps://en.wikipedia.org/wiki/Plasma_torchhttps://en.wikipedia.org/wiki/Plasma_(physics)https://en.wikipedia.org/wiki/Plasma_(physics)https://en.wikipedia.org/wiki/Plasma_(physics)https://en.wikipedia.org/wiki/Plasma_cutting#cite_note-1https://en.wikipedia.org/wiki/Plasma_cutting#cite_note-1https://en.wikipedia.org/wiki/Plasma_cutting#cite_note-1https://en.wikipedia.org/wiki/Plasma_cutting#cite_note-1https://en.wikipedia.org/wiki/Plasma_(physics)https://en.wikipedia.org/wiki/Plasma_torchhttps://en.wikipedia.org/wiki/Metalhttps://en.wikipedia.org/wiki/Steel


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