Plasma Cutting vs. Flame Cutting vs. Waterjet Cutting
There are many different cutting methods to choose from in CNC work, the most effective of which will vary depending on the specifics of your project and the material being cut.
Three of the most popular cutting processes are plasma cutting, flame cutting, and waterjet cutting. Here is a breakdown of the key differences between the three to help you determine which is best for your next project.
Flame cutting – also referred to as oxy-fuel cutting – is a thermal cutting process that combines oxygen and a fuel source (oxy-fuel) to create a flame hot enough to burn through material.
The cutting process starts with a neutral flame from outer jets on the torch that preheat the material to its ignition temperature without melting it. Once that temperature is reached, the machine then releases an additional stream of oxygen through the central jet to intensify the flame. The central jet is capable of being controlled by a trigger for added precision. This added burst of hyper-concentrated heat cuts through the material.
Advantages of flame cutting
Perhaps the greatest advantage of flame cutting is its cost-effectiveness. There are no power supplies needed and not many components required for operation, which also makes it highly portable and great for fieldwork. Flame cutting is also rather powerful and can cut through metal up to several feet thick.
Disadvantages of flame cutting
Flame cutting is, however, a bit lacking in the versatility department. It can only cleanly cut a few types of material, primarily dealing in cast irons, carbon steel, and low alloy steels. It is also less efficient than other options.
Since the temperature of the cut is so hot, material edges can often form into a thin layer of solidified steel (known as the decarburized layer). Depending on the application, this layer may need to be removed after cutting. Surrounding material in the heat affected zone can also be affected by the extreme heat, requiring post-cut treatment in order to avoid hardening and cracking in the future.
Flame cutting is best for portably cutting thick cast irons or steels at a low cost.
Waterjet cutting is a mechanical cutting method that uses a high-pressure stream of water to cut through material. During cutting, a high-pressure pump sends the water through the cutting head at speeds of up to 2,500 feet per second. In order to cut metals and certain other harder materials, an abrasive substance is often added to the water to increase flow rate and cutting ability.
Advantages of waterjet cutting
Waterjet cutting is quite versatile and can cut many different types of materials, including both metals and nonmetals. It’s also a bit safer than thermal cutting methods, as it does not emit toxic fumes into the shop during the process. Since the cut is executed by water rather than heat, there is no risk of thermal damage to the cut area or material.
Disadvantages of waterjet cutting
Waterjet cutting really doesn’t perform well when working with thick cuts on hard metals, which can end up slowing the cut speed and ultimately hampering the quality of the cut. The equipment involved is also a bit more expensive than that of alternative cutting solutions – and requiring of much more maintenance.
Waterjet cutting is best for precision cutting (especially of nonmetals) without fear of heat damage or toxicity.
Much like flame cutting, plasma cutting is a thermal process, but instead of using oxygen and fuel to create a flame, plasma cutting uses an electrical arc to ionize and heat gas that in turn produces plasma to cut the material. During cutting, the workpiece is set as part of the electrical circuit by use of a grounding clamp. The superheated plasma then reaches the pieces and performs the cut.
Advantages of plasma cutting
Plasma cutting is a more efficient form of thermal cutting than flame cutting – but it doesn’t sacrifice any of the quality of the cut, typically achieving a more refined kerf. The process can also be automated, and works well when cutting most conductive metals, such as aluminum, copper, or stainless steel.
Disadvantages of plasma cutting
The only real limitation with plasma cutting is that the material you’re cutting needs to have conductive properties in order to become part of the plasma cutting table’s electrical arc. CNC plasma cutters also typically don’t perform as well when cutting materials more than a few inches thick.
Plasma cutting is best for performing high-quality precision cuts on metals up to three or four inches thick at a more affordable cost than waterjet solutions.
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