The Plasma Cutter uses compressed air and an electric arc to cut metal. The versatile Plasma Cutter is capable of Plasma Cutting just about any metal, including Mild Steel, Stainless Steel and Aluminium.
Plasma Cutters work by forcing compressed air into a chamber that contains a Plasma Electrode and a Plasma Cutting Tip. As the compressed air is forced into the chamber an electric arc is struck between the Plasma Electrode and Plasma Cutting tip. This arc "Plasmarises" the compressed air, making it electrically conductive. This electrically conductive air then escapes the pressurised chamber via a small hole in the Plasma Cutting tip, taking the energy of the arc with it. The heat of the Plasma Arc melts the metal to be cut, while the force of the air blows it away.
Because the stream of plasmarised air is very narrow and the melted metal is blown away, the Plasma Cutter introduces very little heat into the job, thus there is little, or no, distortion of the job. The Plasma cutter also offers a big advantage over more traditional cutting methods in that it operates from only one side and can easily cut any shape, even where there is a second panel behind that is to be left intact.
Two types of Plasma Cutter are available; those with a built in compressor, and those that require an external compressed air supply. Both Plasma Cutters are as effective as each other. Built In Compressor Plasma Cutters are arguably more convenient, as they are self-contained and if only a small job needs to be cut the operator does not need to wait for an external compressor to get up to operating pressure before commencing work. Built in compressor Plasma Cutters are, however, a little more expensive, so choice really depends on individual requirements.
A Plasma cutter is generally selected by cut performance, that is to say how thick it will cut. Plasma cutter cut performance is always quoted for mild steel. Stainless Steel and Aluminium require more power, so generally, cut performance will be less for these materials. Typically, a Plasma Cutter that is quoted as having a max cut capacity of 6mm mild steel, will cut a max thickness of 5mm stainless steel and 3.5mm aluminium, or around 10% and 40% less than mild steel. Care has to be taken with manufacturers claims on Plasma Cutter cut capacity; more honest suppliers will quote a "max or Genuine Cut Capacity" and a "Max Sever". The "max or Genuine Cut Capacity", lets say 6mm, means the Plasma Cutter will cut up to 6mm mild steel, cleanly and at a speed of at least 250mm (10") per minute. "Max Sever", lets say 10mm, is the absolute maximum that the Plasma Cutter will achieve on mild steel, but expect a poor quality cut and VERY slow speed. Unfortunately, some Plasma Cutter suppliers will say "cuts up to 10mm steel" when the thickness they quote is in fact the Max Sever! Obviously, the thinner the metal, the quicker a Plasma Cutter will cut, so as a rule of thumb, we recommend that customers consider a Plasma Cutter with a cut capacity at least 30% greater than they think they will need, that way there is always spare capacity if required and good cut speed on the planned work.
Rutile Flux Coated - The most common type of welding rod coating, rutile coated Arc Welding electrodes are easy to use, offer good levels of mechanical strength and produce a weld of good visual appearance.
Basic Flux Coated - Basic, or Low Hydrogen, welding rod coatings are used for higher strength joints and are recommended for structural Arc Welding applications and materials thicker than 10mm. Basic coated welding rods are more difficult to use than rutile coated welding rods and do not offer such a good weld appearance, they are therefore best chosen by those with experience of welding.
Cellulosic Flux Coated - Best known for deep weld penetration and rapid burn speed, cellulosic coated welding rods are commonly used for professional root Arc Welding of plate and pipe.
Arc Welding Current is largely determined by the type of welding electrode, the type of job and the material to be welded. Most welding rod manufacturers will recommend a current range for a given welding rod, however as a general guide allow 35 amps of welding current for every millimetre of Arc Welding electrode diameter (plus or minus 15% depending on the job) ie: 2.5mm welding electrode = 88 amps (or a range of 75 - 102 amps).
Types of Arc Welding Equipment
There are three types of Arc Welding power source:
Arc Welding Transformer with moving shunt power adjustment - These Arc Welding machines are the cheapest type and rely on winding two parts of a transformer together to adjust power. These welding machines give an AC current otput. Whilst cheap, the AC welding output means that the welding arc tends to be a little difficult to start and, once started, the welding arc will tend to be quite fierce and spattery.
Arc Welding Transformer with potentiometer power adjustment - These Arc Welding machines usually give a DC welding current output. DC welding output offers easier arc starting and a smoother softer arc. This type of Arc Welding equipment has largely been superceded by modern inverter type Arc Welding power sources.
Arc Welding Inverter - These Arc Welding machines have a potentiometer power adjustment and give a DC welding current output for easy arc striking and smoother softer arc. Arc Welding Inverters often have additional features such as "Anti Stick" to reduce the likelihood of the welding electrode sticking to the job and "Arc Force" to make arc striking even easier. Arc Welding Inverters are also light in weight and will run for longer than transformer based welding machines before they overheat.
