History of the Cutters
Back in the 1960s, cutting metal was basically by means of metal to metal. As a result, there were many drawbacks associated with this form of cutting and they had to implement a way to curb this. In welding, using the gas mixture was accompanied by a poor surface finish, untidy surfaces and was so slow. Using the Computer Numerical Control (CNC), it gave a diversity in the shapes and the metal sheet sizes cut, leading to a quick cutting method.
How it works
Air, Oxygen and other unreactive gases compressed in the cutter are channelled to the workpiece under operation. The superheated gas is fed to the workpiece at very high pressure through the nozzle. A metal rod placed between the nozzle and the metal being cut ionizes the plasma forming an arc. This arc causes melting of the metal when in contact, thus the metal is cut. This is an efficietn and quicker method than other methods that were used in the past to cut metal.
They are usually of two categories and are classified according to the type of contact made by the metal being cut and the plasma nozzle. In that respect, they are contact and non-contact plasma arc. In the contact plasma arc, the nozzle makes a contact with the metal cut hence production of ignition spark. In a non-contact one, it makes use of frequency or voltages supplied to the cutter thereby producing ignition sparks.
They are classified according to the mechanism of spark production involved. Some of the processes utilise contact mechanism while others make use of the frequencies or voltage supplied for spark production. This process is categorised into three; contact, Arc Pilot and CNC processes. All these three categories use different cutting tables which are specific to the mechanism used.
Inverter plasma cutter
These are the traditional types, they make use of Field effect transistors for the conversion of AC signal to DC signal. Inverter rating ranges from around 10000HZ to 200000HZ. This frequency is usually associated with power factor correction which limits the efficiency of the cutter. Though nowadays they are using IGBTS rather than the MOSFETs, this ensure no parallel running of transistors.
The CNC process
In this type of cutting, a programming software is incorporated to the cutter and a torch. The program controls the manner in which the torch moves, the rate at which it cuts also determines the cut dimensions of the metal cut. It makes use of the CNC table. The CNC is the recent type of the cutter and can cut thick lead metals.
Contact and Pilot Arc
With the contact process, the user has to keep the nozzle and the metal being cut in contact so as to ensure spark production continues. It uses high-frequency plasma table and is usually used for cutting metals of high conductivity. For the pilot arc, there is no contact between the nozzle and workpiece cut. In such case, the table used produces the arc and the user maintains the separation of the plasma and the workpiece. Mostly it’s used for cutting insulators especially plastics.
Areas of application
With the varying features of plasma cutters, they have diversified areas of applications ranging from simple artisan works to such complex metal works including manufacturing of cars and fabrication of steel. They are used by artisans because they are portable and require less input for work. For commercial production such as car manufacturing, they are of large size and require a quantified amount of input to function. Other areas where they can be used include the metal recycling companies, finishing operation on metal work that’s removing unwanted materials from a workpiece, demolition of unwanted metal structures and many other industrial operations.
A cutter with a rating of about 60Hz costs around $4000 on Amazon. There are, however, other types of cutters with fewer features and limited application areas cheaper and can cost around $1000. It all depends on specifications and the type of metal the cutter is intended to cut.
Like any other machine, there are hazards involved when using this type of cutter. Protective clothing such as overalls, safety boots, gloves and sunglasses should be worn by the user. The sparks associated with plasma cutting are often at high risks of causing a fire, so to ensure no fire hazards associated when using it, it is important to keep away highly flammable such petrol, kerosene or diesel substances from the area of operation.
They have quite a number of advantages;
They have few disadvantages;
These cutters are so far the basic metal cutters for all cutting operations. They have a wide array of benefits such as cutting thick and electric conductors make them unique for many operations. Since they incorporate the use of a computer aided mechanism that ensures speed, accuracy and precision, they are emerging as the choice for large manufacturing operations cutting. These cutters are easy to install and the cost of purchasing and maintaining is also low. So they are affordable to the people who may need them. Also, operating these cutters is not complicated. They are easier to use and anybody with a mere cutting skill can use them.