Plasma Cutter

PLASMA CUTTER

PlasmaCutting is a very interesting field of physical sciences that will always intrigue anyone who has the attraction to the dynamics of science.

Before going into a deep interrogation of plasma cutting, it is vital that we first understand what plasma is.

 I am pretty convinced that you are well vast with the three states of matter which are solid, liquid and gas. For water which is a very common element to us, ice, water and steam are its subsequent states of matter dependent on how much energy is applied or reduced from or on them.

When more energy is introduced to ice, its kinetic energy rises and water is then formed as a result of the ice melting. As we continue adding energy in the form of heat to the water, vapor is formed. This then leads to the vapor decomposing to hydrogen and oxygen in form of steam.

By adding more and more energy to the steam, the oxygen and hydrogen gas making it upbecome ionized, a process that makes them electronically conductive. The end product then is an electrically conductive gas that is at the same time ionized named as plasma.

Plasma cutting

Most metals have been known to possess very tough surfaces that have been known to provide a kind of impenetrable cocoons. However after the discovery of plasma, electronically conductive metals like brass, aluminum etc, can be cut using plasma gas.  The gas is used to transfer energy from an electrical power source to the material being cut by the use of a plasma torch.

Components of a basic plasma cutting system

 

·         Power supply

·         Arc starting circuit

·         A torch

The above mentioned basic components provide very important aspects in the system. First, they allow for proper control of the plasma cutting system, they also provide a good ionization capability for the gas and also provide electrical power which is the key propelling energy sustaining the cutting process.

Power supply

 

Plasma Cutting is supplied by a constant Direct Current power supply system. The voltage that passes through the system is of a range of 240 to 400 volts. The speed of the cutting process is determined by the output current of the power supply while the same output amperage also determines the cut thickness.

The sole purpose of the power supply is to provide the appropriate amount of energy to maintain and keep the system working immediately after ionization process.

Arc starting circuit

 

This is a generator system that runs at very high frequency producing an Alternating Current voltage that ranges between 5000 volts to 10000volts at a frequency of approximately 2 megahertz.

High intensity arc inside the torch is created by this high voltage, the torch then causes an ionizing effect to the gas hence creating the plasma.

The Torch

 

This is now the holder of the nozzle to be consumed and also the electrode. Besides these, it also provides cooling effect which can be in the form of water or gas to the parts exposed to friction: nozzle and the electrode, while at the same time ensuring that the plasma jet is well maintained.

Series of operating a plasma cutter

 

Interconnecting leads and cables connect to the torch after sourcing power from the power supply.  The leads and the cables ensure that there is convenient gas flow while alsoassuring that current flows at remarkably high frequency towards the torch so that the process starts well and is also maintained.

When an ON signal is sent to the power supply, gas and current flow to the torch start simultaneously as they become activated.

The metal to be cut should then be connected directly to the positive while the nozzle is connected to the negative in the power supply that must also consist of a resistor and a relay.The gas then should flow through the nozzle exits.

After it is established that the gas flow has stabilized, the activation of high frequency circuit is initiated. This causes the high frequency to breakdown amid the nozzle and inside the torch in a way that the gas must go past this arc before being let out by the nozzle. The energy transfer causes an ionization effect to the gas hence becoming able to conduct electricity. The gas then creates a current path between the nozzle and electrode hence resulting to plasma that goes out through the nozzle.

If the nozzle is close enough to the metal, the pilot arc will attach to the work piece.  The ionization of the gas is then continued to be maintained by the drive from the main Direct Current arc.

Owing to the high temperature of the plasma, the metal melts while at the same time the fast flowing gas blows away the molten material. Perhaps at this time, the cutting process is started.

Convectional plasma cutting and how to vary the process.

The nitrogen or air used provides a cooling effect and also produces the plasma. The rating of plasma systems are usually under 100Amps, this is for cutting material below 5/8 inches thick.

Cutting using two gases

 

When two types of gases are used, one is usually for the plasma while the other is a guard gas. The guard gas shields the cut area from the atmosphere henceforward producing a cleaner cut edge.

More gas combinations when used, they produceexcellent quality cut off the work piece material.

Water shielded cutting

 

Here water is substituted for the shield gas. The water provides a cooling effect that goes along with better quality of cuts on stainless steel.

Water injection plasma cutting

A single gas is used here for plasma utilizing water radically or spin injected directly in to the arc. This increases constriction resulting to improved density and temperature of the arc. This type of process is strictly for mechanized applications.

Precision plasma cutting

Precision plasma cutting produces excellentcuttings especially on less thick materials which are 0.5 inches or even less but at gentler speeds. This latest discovery in cooperates the super constriction of the arc that in turn increases the density of energy.

Less fast speeds are needed to allow the device cut more accurately.  Precision plasma cutting is also strictly for the mechanized applications only.