Oxy Fuel Vs Plasma Cutting | Everything You Need to Know

For all metal fabricators around the world, metal sheet and tube cutting is a necessary job to do. A cnc machine that can cut metal is necessary for metal fabrication shops. Generally, we have three kinds of machines that can do this job: cnc oxy-fuel cutting by Oxyacetylene, cnc plasma cutter machine, and fiber laser cutting machine. A fiber laser cutting machine is necessary if you have extremely high requirements for cutting speed and accuracy. Generally speaking, for most metal-cutting jobs, a cnc oxyfuel or plasma cutting machine is enough.

How should we choose between oxyfuel cutting and plasma cutting? What differences do the two metal cutting methods have? This article will discuss them in detail.

CNC oxy-fuel cutting by Oxyacetylene, as the name implies, we cut metal by flame.

What Is Oxy Fuel Cutting?

Oxy fuel cutting refers to a method using a cutting torch to generate an oxyacetylene flame, which is the same as a welding torch. The torch preheats the steel plate to about 870ºC or higher. Then, pure high-pressure oxygen is sprayed from another pipe of the cutting torch, causing a violent chemical combustion reaction between the iron elements in the steel plate and the oxygen. Molten iron elements are sprayed away by high-pressure oxygen to form cuts.

What Is Plasma Cutting?

Plasma cutting means cutting metal with plasma. High-frequency arc causes the gas to "break down" or ionize it into basic atomic particles, thereby creating a "plasma." Then, the arc jumps to the metal workpiece, and the high-pressure gas blows the plasma out of the cutting torch burner with an exit speed of 800 to 1,000 meters per second (about Mach 3). In this way, the high energy released when the various gases in the combined plasma return to their normal state generates a high temperature of 2700°C. This temperature is almost twice the melting point of a metal sheet. As a result, the metal workpiece is quickly melted, and the molten metal is blown away by the jet of high-pressure air.

Now that the two cutting principles are clear, let’s compare the differences in the processing of the two cutting methods.

What Is the Difference Between Plasma Cutting and Oxyfuel Cutting? ( Plasma Cutter VS Oxy Acetylene)

Cutting material and thickness

Oxyacetylene cutting is suitable for thick steel plates. However, if the steel plate contains too high levels of anti-oxidation alloying elements such as chromium, nickel, and molybdenum or is very thin, plasma cutting is necessary.

With different working gases, plasma cutting machines can cut various metals that are difficult to cut with oxygen cutting. Especially for non-ferrous metals (stainless steel, aluminum, copper, titanium, nickel), the cutting effect is better, and the surface will not turn black. Moreover, plasma cutting speed is fast when cutting thinner metal sheets. Especially when cutting ordinary carbon steel thin plates, the speed can be up to 5 to 6 times that of oxygen cutting. The cutting surface is smooth, the thermal deformation is small, and there is almost no thermal impact district.

Cost

The initial purchase cost of a CNC plasma cutting machine will be higher than that of oxyacetylene cutting.

But oxyacetylene cutting is an example of cheap to buy but expensive to use. The cost of consumables for the two machines is similar. Compared with plasma cutting, which only needs electricity to run, Oxyacetylene cutting has a higher cost because it needs a constant supply of fuel.

The main cost of plasma cutting is the cost of consumable electrodes and nozzles. The cost of oxyacetylene cutting is mainly the cost of oxygen and acetylene. Now, the two cutting costs are calculated as follows:

Cost of cutting by cnc oxyfuel

Cost of cutting a steel plate with a thickness of 18mm and a length of 1 meter by oxygen:

Therefore, the cost of oxygen consumption for cutting one meter of steel plate is:

3.65÷60÷0.52=0.12 (m³)

0.12 x 4.75 = 0.57 (RMB)

Cost of cutting a steel plate with a thickness of 18mm and a length of 1 meter by acetylene:

0.73÷60÷0.52=0.024 (m³)

14x0.024 = 0.34(RMB)

So the total cost is 0.57+0.34=0.91(RMB)

Cost of cutting by cnc plasma

Using the American Hypertherm Company's MAX200 as an example, let's calculate the cost of cutting a 1m long and 18mm thick steel plate with a CNC plasma machine.

A 200A power supply with a power of about 30kw consumes 30-kilowatt hours of electricity per hour. The industrial electricity fee is 0.8 RMB per hour, so the electricity fee is 24 RMB. The original electrode cutting nozzle costs 100 yuan per set, and the service life of each set is 5 hours. 0.2 sets of electrode cutting tips are consumed per hour. Therefore, the loss cost of the electrode and cutting nozzle is 20 RMB per hour.

The total cost per minute to cut one meter of steel plate with plasma is:

(24+20) ÷60÷1.5=0.49 (RMB)

Through the above comparison, we can see that in actual use, plasma has a faster cutting speed, which is twice that of oxyacetylene, and a lower cost.

Waste Production

Since oxygen reacts with metal to produce iron oxide, cutting metal with oxyacetylene will produce a large amount of slag. This will require extensive cleanup before proceeding to the next step.

Plasma cutting still produces furnaces, but not nearly as much as oxyacetylene cutting. The amount of slag produced by a plasma cutter depends on factors such as torch design and arc energy density.

Through the above comparison, I think you should have a clear idea of how to choose a suitable machine for your metal processing work.

If you have any questions or concerns, please feel free to contact us. EagleTec CNC will provide you with professional solutions.

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