As we know, the matter is of three types – solid, liquid, and gas. Matter changes from one state to another by the introduction or reduction of energy like heat. Now, plasma is the fourth type of matter. If heat is applied to the liquid, it changes to a gaseous state. If the gas is again heated, it ionizes and becomes conductive to electricity and becomes plasma.
How does a plasma cutter work?
A plasma cutter uses this electrically conductive gas to transfer energy from a power source to a conductive material, thereby resulting in faster and cleaner cutting process than oxy-fuel. A plasma torch produces a high-temperature plasma jet of nearly 40,000°F which enables it to cut efficiently through hard surfaces. Plasma jet is created when transmission of energy takes place to a metal conductor from a power source, and gas like oxygen or just air is passed through a very narrow opening in a nozzle resulting in a plasma arc formed. The metal changes into its molten state and is discarded merely off.
A plasma cutting system consists of the following components:
This converts three-phase or single AC line into a constant and smooth DC voltage that ranges from 200-500VDC. The voltage is responsible for maintaining the plasma arc throughout the cut and regulates the current output based on the thickness and the material type that is being processed.
2. Starting arc console
The spark inside the plasma torch is created by the ASC circuit that gives out approximately 5,000 VAC AC voltage that is used to generate a plasma arc.
3. Plasma Torch
The primary function of the primary torch is to provide proper cooling and alignment of the consumables. The main consumable part required for plasma arc generation are the nozzle, swirl ring, and the electrode. In most cases, an extra shielding cap may be used to improve the cut quality more, and all the parts are kept together by outer and inner caps.
Most plasma torches can be categorised into two types – precision and conventional torches.
1. Precision torches
High current density or precision plasma torches are engineered and designed to produce the highest and sharpest quality cuts achievable. There are tons of cutting guide available from distributors like Tanjant Tools instructions and using guide. The consumable designs and the torch are more complex and additional pieces may be required to shape and constrict the arc further. This plasma’s amperage is about 40-50K amps per square inch and several gases like nitrogen, highly pure air, and oxygen is mixed with a nitrogen/argon/hydrogen mixture to be used as a gas for the best results on several types of conductive materials.
2. Conventional torches
These plasma torches mostly use shop air as plasma gasses. The nozzle’s orifice defines the shape of the plasma arc. With 12-20K amps per square of amperage. All sorts of hand-held systems use this kind of plasma torch and at some mechanised applications as well.
Components of a plasma torch
Putting together a decent plasma system can be a difficult task. It all begins with a machine that generates the stream of plasma, the X-Y table, ventilation system, software, and a CNC.
The X-Y table includes drivers and motors that provide accurate and coordinated motions for several types of torches, be it oxy-fuel or plasma. Earlier, the main application of the X-Y table was limited to shipbuilding and heavy equipment industries. These machines were designed to be strong enough to stand for several decades to come and to produce tons of metal parts with minimal maintenance. Today, there is no shortage of X-Y table styles.
Next, every X-Y table must have the CNC component. It is the brains of the machine that converts the cutting program into electrical instructions that control the cutting speed and direction. The CNC also provides information and instructions to peripheral equipment, height controller, and the plasma cutter. The industrial-grade computer’s internal motion and machine-control software controls take orders from the CAM software (manufacturing industry software that is used to design and deals with the machine’s capability to work on that task) and machine operator and convert these orders into functions by controlling the drive systems. These industrial CNCs are developed to withstand the rough work environment like smoke and debris from welding and cutting processes, machine and electricity interference vibrations from machines, etc. Drive electronics like steppers are cheaper and more straightforward than servo systems and are often controlled by laptop and computers. Servos are more intuitive for machine operators as they use feedback encoder to the CNC, thereby resulting in fewer chances of lost positioning on the cutting table in an event like cutting interruption, power failure, or tipped-up part.
Mechanical components of a plasma torch include some moving parts like torch height control, torch carriage, and gantry. For large industrial machines, all these components are heavy-duty and sturdy. The heavier the device, the more powerful drive motors and the weight-bearing systems are. Modern mechanical parts provide excellent precision have more extensive torque range and speed that is beneficial for extremely slow or fast speeds.
Automatic height is an optional feature that is well rewarding in most cases. Effective cutting via a plasma torch requires three modes of height – two for cutting and one for piercing. This maximises the cut quality and consumable life of the plasma torch. The piercing torch plays the most critical role when it comes to cut quality and nozzle life. The system advances the plasma torch till it finds the surface of the material you wish to cut and retracts to a proper height. One wrong pierce can affect the cut’s overall edge quality dross, and angularity permanently.
Plasma torches have come a long way the heavy first-generation counterparts to a machine that looks like a child’s toy today. Today, these machines come in different models and styles that are suitable for a variety of operations. New technology, ranging from televisions to automobiles, have gone through an evolutionary period. Such is the case with plasma torches as well. These machines have become more reliable, capable and smaller and ready to withstand the harsh conditions of the industry.