A Comprehensive Overview of CNC Plasma Cutting Machine

Posted on Nov 27, 2020

CNC plasma cutting machine

A CNC plasma cutting machine, also known as the CNC plasma cutter, is commonly used for cutting metals for a wide variety of purposes.

The Basics

A CNC plasma cutting machine, also known as the CNC plasma cutter, is commonly used for cutting metals for a wide variety of purposes. The plasma CNC machine is the machine that applies the plasma cutting approach in CNC machining. In a conventional CNC machining operation, drill bits or cutting tools are used to cut the workpieces or remove the unwanted parts away from the workpieces by the physical force of piercing, penetrating, or slicing. On the other hand, a plasma CNC machine does not use the conventional cutting tools but a jet of hot plasma instead.

These type of machines are especiallyu sutiable for machining operations thati nvolve electrically conductive materials. For example, materials such as steel, stainless steel, aluminum, brass or copper can all be cut by a plasma torch . There are more metal materials that can be cut with the plasma CNC machines. The plasma cutting can also be applied in other industrial settings such as fabrication, auto repair and restoration, construction, etc.

What Is Plasma?

    Plasma is considered the fourth state of matter other than solid, liquid and gas. As we know, a matter changes its state from one to another through the change of temperature, heating or cooling. The nature of the temperature change is the dynamic of energy. The basic rule goes like this, when a solid matter is heated, it gradually melts and turns into liquid. When it is further heated, the liquid evaporates into gas. So where is plasma in it?

    To put it simple and straight, when the gas or the steam is even further heated, the gas becomes ionized and electrically conductive and turns into plasma. A plasma cutter transfers the energy from the electrically conductive gas to the electrically conductive materials, the metal workpieces. The process that transfers energy from plasma to the workpieces causes the removal of the parts the plasma contacts.

The way the parts of the workpieces are removed or dissected by plasma is more similar to that of electrical discharge machining or the laser cutting than the traditional CNC machining. Instead of physically dissecting the parts of the workpiece, the plasma melts or evaporates the parts away. Plasma cutting is deemed as one of the precision cutting measures in CNC machining.

Construction and Working Principle

There are three essential components of a plasma CNC machine: the power supply, the plasma arc starting console, and the plasma torch. The power supply of a plasma cutter converts the AC voltage into a constant DC voltage which ranges from 200 to 400 VDC. The DC voltage has to be constant to maintain the plasma arc during the cutting process. The power supply system also controls the current output based on the amount it needs to cut through certain types and thickness of materials. The thicker or more rigid the workpiece is, the greater output of electric current is required.

A CNC plasma machine typically carries a plasma torch, and the torch can be moved in a path directed by a computer. The term "CNC" is referred to as "Computer Numerical Control", meaning that a computer is used to direct the machine's motion based on numerical codes in a program.

The torch of the CNC plasma cutting machine can cut into steel, stainless steel, aluminum, brass, and copper, as well as other conductive metals. It is often deployed in fabrication shops, automotive repair and restoration workshops, industrial constructions, or salvaging and scrapping operations.

Due to the high speed and precise nature of these cutters, the utilization of plasma cutting has been widespread from large-scale industrial CNC applications down to small hobbyist shops. But there are even more crucial components worth taking a look at:

All of the electronics in the CNC and drive system work and communicate very quickly, often measuring and updating position information every few milliseconds. This allows the machine motion to be smooth and accurate enough to produce plasma cut parts with a smooth, straight, consistent edge quality, and precise part dimensions.

  • Torch and Torch Controller: To cut parts from metal plates, the CNC directs the motion of the torch. A part program is then responsible for telling the torch when to turn on and off. These part programs are normally created by a piece of software referred to as the "post-processor", which can take a part geometry from a CAD file and translate it into a language (usually referred to as the M-codes and G-codes) that the CNC is able to read.
  • Drive System: A CNC plasma cutting machine also includes a drive system that comprises drive amplifiers, motors, encoders, and cables. There are at least two motors for the X-axis and the Y-axis, respectively. There is then a driver amplifier for each motor, which takes a low power signal from the CNC and transforms it into a high power signal to initiate the motor. Each axis incorporates a feedback mechanism, typically an encoder, which generates a digital signal to indicate how far the axis has traveled. Cables then direct the power to the motor from the amplifier and carry the position signals from the encoder back to the CNC.
  • I/O System: CNC plasma cutter will have an electrical system that takes care of the inputs and outputs. This is essentially how plasma is turned on by the CNC at the optimal time. For instance, this can be done by turning on an output that closes a relay. The CNC of the plasma cutter uses inputs as a prompt to when the plasma arc has initiated and is poised to move. Those are the most fundamental inputs and outputs required, but obviously, there can be many more.

Many other features can be supplemented to the CNC plasma cutter, such as arc voltage height control systems, plasma bevel systems, integrated plasma control systems, and so on. Nevertheless, the basics of a CNC plasma cutter described above will be common to all such machines, from the simplest to the most complicated.


Working Principle Explained

As mentioned above, the plasma gas is actuated by the arcs that are generated by the electrode from the power source. The first is the pilot arc and followed by the main arc. 

When the power source is operated, it would apply the negative voltage to the electrode, which is the cathode of the pilot arc circuit. Then a temporary, positive voltage was placed on the nozzle, which is the anode of the pilot arc circuit, and the pilot arc would then be initiated. As the pilot arc flows through the nozzle opening to the workpiece, the main arc circuit would be generated and the actual cutting operation would be driven to increase to optimal cutting amperage.

When the nozzle is opened by the main arc, the plasma machine would produce plasma up to 20,000°C and move towards the workpiece. Once the heat is given to the workpiece, the localized workpiece starts to melt by the vaporized plasma gas. After the localized workpiece is completely weakened, the desired parts of the material on the workpiece would start to be removed. At that time, the current and the nozzle would control the flow of the plasma gas, in order to pursue the most precise cuts and reduce the deformation of the products.

When everything is ready, the torch of the plasma machine would follow the instructions of the CNC program, to move across the surface of the workpiece with appropriate speed and required movement. After that, the desired cuts would be made on the workpiece with the optimal precision and smooth finishes as necessary.

Advantags & Costs

CNC controlled plasma machines ensure the optimal precision of the final parts. In addition, even the thicker materials can be processed simply by the adjustment of the power source. Therefore, they can be used in a variety of applications. Furthermore, plasma cutters allow for lower equipment and operational costs, which makes it a cutting machine with high value and effectiveness.


CNC plasma cutters, particularly the torches, were once quite expensive. For this reason, they were usually only found in professional welding shops and very well-stocked private garages and shops. However, modern plasma torches are becoming cheaper and now are within the price range of many hobbyists, which can be less than $300.

Older units may be very heavy, but still portable, while some newer ones with inverter technology weigh only a little, yet equal or exceed the capacities of older ones.


Operator Safety for Plasma-related Machining

To ensure the safety of those operating a CNC plasma cutter, proper eye protection, and face shields are needed to prevent eye damage (i.e. arc eyes) as well as damage from debris.

Leather gloves, an apron, and a jacket are also recommended to prevent burns from sparks and hot metal. Working in a clean area free of flammable liquids, materials and gases are very important. Sparks and hot metal from a plasma cutter can quickly cause fires if they are not isolated from flammable objects.

Plasma cutters can send hot sparks flying up to 5 feet away in certain situations. The operator of the machine is typically blind to any fire that has started because they are behind their face shield. Take safety precautions to make sure your work area is free of fire hazards.


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