When considering a capital equipment investment the big question metal cutting shops ponder is the superiority between using oxy-fuel or plasma cutting for their applications. While each process has its niche, the answer to which process is superior is, “it depends”. Developed in 1950, the perception was that Plasma Cutting is a more complex cutting process compared to oxy-fuel. While this ideal has been carried through over the years, modern plasma machines are becoming more technologically advanced as it provides easier operation and higher consistency than oxy-fuel. These advancements have reduced complexity and now forces individuals to weigh the cost-benefits between using the different processes.
Some things to consider when choosing an oxy-fuel or plasma process are:
How it works: Plasma cutting is the process of adding energy to an electrically neutral gas; the energy added is electricity and the gas is compressed air. Increasing the amperage on the power supply translates into added electricity thus creating a hotter plasma arc. This electricity is then forced through a nozzle inside the plasma torch constricting the arc so it can precisely cut through metals. Oxy-fuel cutting on the other hand requires pre-heating of the metal until its temperature reaches the point where a high-power torch can direct a stream of oxygen through the material to burn the metal away.
Material Type: Plasma is capable of cutting materials up to 2” thick and works on all electricity conductive materials including: steel, aluminum, copper, bronze, stainless steel, etc. Oxy-fuel cutting is more limited and best applicable for ferrous (iron-containing) steels up to 24” thick. Note: oxy-fuel cannot cut aluminum or stainless steel.
Cutting Speed: When it comes to the speed of production plasma can cut up to 6x faster than oxy-fuel and prep time is minimal as pre-heating is not required.
Power Source: Plasma requires a primary power source; electricity. Since oxy-fuel is not dependent on a primary power source it is essentially capable of cutting in any location with a gas tank and torches. This gives an advantage to manufacturers with dispersed work in terms of location.
Safety: Oxyfuel is a mixture of oxygen and a fuel gas. The most common fuel gases are acetylene, propane, MAPP, propylene, and natural gas. Acetylene is usually the most popular because it creates a hotter flame and therefore faster piercing. However, because acetylene is an unstable and highly flammable gas, an acetylene explosion could possibly occur. Plasma systems typically run on compressed air, eliminating the need for flammable gases. Operators can also reduce noise and fumes by using a water table as opposed to a downdraft table.
Cost: With regards to initial investment, plasma systems require a higher capital outlay. However, if you take into account the purchasing of gas and the cutting limitations oxy-fuel systems are associated with, it can be seen as more costly in the long-run. With Plasma, the main costs after installation are consumables and because it can cut at a much faster rate this significantly increases productivity.
Before choosing your cutting process it is wise to consider material thickness, material type, equipment location, power resources, fixed and variable costs, and your required speed of production. Oxy-fuel and plasma cutting have their own advantages and disadvantages. It all comes down to the nature of your operation.