Today we would like to introduce you to a sheet-cutting process that most people probably associate with highly professional machinery. Of course, metalworking companies - like us - rely on computer-controlled machines for plasma cutting. But that does not mean you cannot also work with this process at home and by hand - unlike laser cutting.
We want to explain what matters in plasma cutting. Then you can decide whether the advantages outweigh the effort for you and you want to try plasma cutting yourself, or whether you would rather leave millimetre-precise sheet cutting to the professionals. In that case, our offer could be of interest to you - more on that later.
What is plasma cutting?
It is a process for severing metals that belongs to the group of arc cutting processes. It is used above all for high-alloy steels, copper and aluminium. Unlike a flame cutter, cutting with a plasma jet essentially triggers no chemical reaction with the metal being cut. This is because the molten metal does not remain at the cut but is blown away by the gas flowing out at high pressure.
To start plasma cutting, ignition gas must first be supplied - in practice, usually argon. The cutting process is then set in motion by igniting the pilot arc between the electrode and the nozzle. The pilot arc's task is to ionise the path from the workpiece to the electrode.
As soon as the pilot arc touches the workpiece, argon must be supplied so that the main arc, which will perform the cut, can be activated. Due to the large amount of thermal energy generated, the workpiece's state of matter changes: it is melted, and the plasma cut becomes possible.
What are the advantages of plasma cutting?
There are several arguments for cutting metal with a plasma jet. The plasma cutting speed is higher than with other processes. The condition of the workpiece also plays no role: it can be rusty or painted for plasma cutting without affecting the cutting result.
The kerf is narrower than with flame cutting, making finer, more exact cuts possible. The process can be used for all metals and for both very thin and thick sheets - a 10 mm stainless steel plate is no problem for a plasma cutter. This makes it a very good all-round process for sheet cutting.
Which technical requirements are there?
If you want to cut sheets and metal with compressed-air plasma cutting in future, you naturally need to buy a plasma cutter. You will also need to obtain a gas cylinder containing the cutting gas of your choice from a specialist dealer, plus protective equipment similar to that used for welding.
Due to the high temperatures generated during plasma cutting, some components of a plasma cutter wear out very quickly. The electrode and plasma nozzle in particular must be replaced regularly to keep obtaining an exact plasma cut. The service life of these wearing parts can be influenced by the choice of cutting gas, the number of ignitions and the level of the cutting current.
Various gases are suitable for plasma cutting
Since you have to obtain gas for your plasma jet anyway, you should think in advance about which gas or gas mixture to use as the cutting gas. There are real differences in application, which we are happy to explain. The choice of gas lets you influence the economy of cutting - and the quality, and thus the need for rework, can also be controlled through different gases.
Nitrogen
To cut both quickly and free of oxide formation, you should use nitrogen, especially for thin sheets of high-alloy steels. However, non-parallel cut edges can occur. You must therefore pay close attention to the gas quantity supplied and to the plasma cutting speed. Never work in a rush - it has a negative effect on the result.
Oxygen
This cutting gas is mostly used when unalloyed or low-alloy steel is to be cut. Due to its affinity for iron, such sheets can be cut at increased cutting speed. When oxygen is used, one speaks of a fusion cutting process, as melting proceeds too slowly and the molten material cannot flow away.
Air
It sounds almost too banal. But because our atmospheric air consists largely of oxygen and nitrogen, the properties of these two gases can be combined. A further advantage is that air is available in unlimited quantities and free of charge.
Argon-hydrogen mixture
For plasma cutting aluminium and high-alloy steels, a mixture of hydrogen and argon is popular. It enables an increase in plasma cutting speed and also improves the cutting result. An argon-hydrogen mixture is often used for thick sheets.
Nitrogen-hydrogen mixture
This mixture is primarily used as a secondary gas. The hydrogen has a reducing effect and leads to oxide-free cut edges. If you use this mixture as the cutting gas, you can work at relatively high speed, and the cut pattern is very parallel.
What you need to consider in plasma cutting
Since a great deal of heat is generated when you cut sheets with a plasma jet, you must think carefully about the order in which you cut so that the heat can dissipate well. Always start with internal cuts and make sure that parts you have completely severed can fall away. This quickly allows plenty of cooling air to reach your workpiece.
Your finished workpiece should remain connected to the raw sheet for as long as possible. Always try to complete all other cuts before severing your workpiece. That way you can work on it securely clamped and do not have to search for a new position for further plasma cutting.
Shall we take on the cutting for you?
Now that you know how plasma cutting works technically, you will surely have made a decision. Do you want to cut sheets yourself, or shall we take it on for you? We have specialised in cutting, bending and surface-treating sheets on behalf of our customers. Our offer is also aimed at private customers who only need one or a few sheets in individual dimensions.
Our sales team can give you a non-binding quotation for sheet cutting on the phone. But first, they will find out which alloy is the best choice for you. We stock all common alloys to European standards and can also source other sheets for you on request. The lean structures at our plant near Magdeburg mean we can complete almost every order within 48 hours: within two days, we process a sheet to your specifications and hand it over for dispatch. And of course, we use plasma cutters in the process too.
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