Plasma Cutting Equipment Information
Plasma cutting machines cut materials and metals using a stream of high-velocity ionized gas, known as plasma, as a heat source. These devices require a supply of compressed air or gas with an adequate flow rate and pressure. They focus a narrow stream of plasma on a small section of the working surface, which heats and melts the material. The ionized gas removes any molten material through the cut.
Plasma machines are suitable for cutting steel and other conductive alloys such as carbon steel, aluminum, nickel, and titanium. Oxy-fuel cutting, a more conventional method, severs the metal by burning or oxidizing it. Its function is limited to steel and several ferrous metals supporting the oxidizing process. Plasma cutting does not rely on oxidation and is effective on non-ferrous metals that are resistant to the oxy-fuel method.
The plasma method is preferred over other cutting methods due to its precision and superior cutting and piercing speeds that produce exceptional cut quality. Known for their versatility, speed, and quality, plasma machines are an ideal solution for effectively cutting conductive metals and alloys up to 3" in thickness.
Plasma cutting equipment differs in cost, features, and types of material they can cut. These materials include:
- Mild steel
- Stainless steel
- Sheet metal
- Other electrically conductive metals
Plasma cutting processes rely on a jet of ionized gas that melts and severs a material. The gas is heated to a temperature of over 20,000° C and an electric arc forms between an electrode and the workpiece. The electrode is positioned in a gas nozzle cooled by water or air, which constricts the arc forming a narrow, high-velocity, high-temperature stream of plasma.
When the plasma jet strikes the workpiece, it transfers intense heat due to ion recombination, causing the gas to return to its normal state. The heat melts the metal material, and the stream of gas blows the molten material away through the cut. During this process, the surface around the cutting area remains cool. Standard gases used in plasma cutting include argon, nitrogen, hydrogen, or an argon/hydrogen combination. Integration of compressed air makes the plasma method more competitive to oxy-fuel cutting of carbon-manganese and stainless steels. Whereas, inert gasses are effective for high-quality cutting of reactive alloys.
As the plasma device moves along the surface, it produces a clean, linear cut with little minimal slag or dross. The width of the melted zone can be less than 1/16" (1.6mm). Temperatures generated during the process reach up to 16,600° C. Piercing the metal at an acute angle of approximately 60 degrees produces the best results. An excessive amperage or inadequate gas flow can cause the formation of a double arc, leading to a significant reduction in nozzle life.
Plasma cutting machines offer a broad range of features, including:
- Manual operation
- Automatic operation
- Continuous output control
- Touch start operation
- Multiple axis cutting machine design
- Industrial grade shape cutting controller
- Relay based I/O
- Support for advanced plasma features
- Torch height control
- USB port
- CNC (computer numerical control) functionality
- Arc voltage height control
- Extended stroke high body alignment (for increased steel tube cutting capacity)
- Extended length table (for greater cutting area)
- CCD camera (aligns a torch for cutting)
- Touch screen controller
- Torch attachment (extends maximum cutting thickness)
- Precision linear rails (minimizes vibration while cutting)
- Non-high-frequency starting
- Electronic pilot arc circuit controls
- Motorized lifter
- Ohnic touch height sensing (finds plate surface and set piercing height)
- Tool-free quick disconnect torch (enables unplugging the power supply without using tools to switch to manual operation)
Plasma cutting technology is suited for a range of applications, including:
- Shipyard manufacturing
- Maintenance and repair
- Trade schools
- Construction sites
Selecting Plasma Cutting Machines
A variety of factors should be considered when selecting a plasma cutting machine. To start, determine the thickness of the material cut on a frequent basis. Higher amperage machines are better suited for thicker materials while lower amperage machines provide better control and cuts on thinner materials.
Other factors to consider are the machine's starting cycle and visibility. Plasma machines using high frequency starting interfere with computers and other nearby electronic devices. Machines with alternative starting methods exist to address such problems. Application of a smaller torch or an extended nozzle facilitates the working visibility, which is critical in achieving cutting accuracy.
Plasma machines operate at extreme temperatures and use a high voltage spark to initiate the process. Evaluate safety features integrated into the machines, such as safety sensors that prevent an arc from starting unless a nozzle is in place, to avoid exposure to hazardous conditions.
BS EN 50192 - Plasma cutting system for manual use