Plasma cutting for the first time: What to expect?
Plasma cutters use a pilot arc of plasma,a gush of ionized gas that is generated using electricity and compressed air, to cut through metal surfaces.
Hand-held plasma cutters are used to cut metals of thickness up to 40 mm, and automated plasma cutters can cut thicker metals up to 150 mm.
Hand-held plasma cutters arewidely used by individuals for both domestic and commercial purposes.
Hand-held cutter is the size of a light torch, and is attached to a heavy cable from the power supply.
The electricity required by plasma cutters to ionize gases and produce plasma arc is provided by heavy duty power sources.
The hand-held cutter basically contains a torch head and a nozzle through which the compressed air is blown at high speeds.
An electric arc generated between the electrode in the nozzle and the metal work piece ionizes the gases into plasma when the metal comes in contact with the torch using a grounding clamp and completes the circuit.
The very high kinetic energy and high temperature of the plasma arc melts the metal and blows off the liquid, thus making cuts through the metal.
The plasma arc produced enables to cut through thick and thin metal surfaces seamlessly, without application of any physical pressure as in case of a hand-held saw cutters.
How to hold the plasma cutter at the right position to make qualitycuts?
Holding the cutter at the right angle, guiding the direction of the cutter, and moving it at the right speed can be tricky for first timers.
Many beginners find it hard to use plasma cutters as one can neither feel the metal surface nor the plasma arc physically to determine the direction of the cutter. Y
ou can neither feel the pressure of the cutter to guide its direction. The cutter has to be held less than an inch above the surface to provide length to the arc.
The key skill in plasma cutting lies in maneuvering the torch on the workpiece at the right speed, position, angle and direction. This only gets better by practice.
The torches have a grounding clamp that can be attached to the metal surface to be cut which helps complete the circuit from the electric arc to produce plasma.
The cuts on the metal are usually done from outside to inside starting from the edge of the metalwith a plasma cutter.
The nozzle must be held at right angles at the edge of the metal, and the trigger on the torch head be pushed to start the pilot arc.
Holding the arc at 45 degree angle provides some visibility to the arc. As soon as the arc begins, you need to start moving the torch steadily across the metal.
Make sure you adjust and maintain the speed such that sparks go through the metal to melt and liquefy them. Thicker metals have to be cut at slower speeds.
The torch must be held such that the molten metal must always be blow away from you. Moving it too fast doesn’t allow the sparks to pass through the metal and cut all the way through. Once done, pause and switch off the trigger.
The flow of arc continues up to 30 seconds after releasing the trigger, so be cautious. If you need to change the direction of cutting, you need to adjust position and restart the trigger.
It is always advisable that the workstation has enough room for movement given the gases and high temperatures involved.
Hand-held plasma cutters cut very speedily, in few seconds, compared to hand-held saw cutters. They are highly efficient and effortless once you get the hang of it.
However, you have to determine the optimal speed for different thickness of metals. Manufactures specify cutting speeds for different thickness of metal and it is measured in inches per minute (IPM). A ¼” material can be cut by a machine with either higher amperage or lower amperage.
Although both do the job, the speed and quality of the higher amperage machine is better. In addition, the plasma cutters with higher amp cut through metals faster than lower amp ones.
A good rule of thumb is to use a machine which can handle nearly twice your actual cutting thickness. For example, it will be faster to use a 1/2″ machine to perform good quality and long cuts on ¼” material.
Precautions to be takenwhile plasma cutting
Firstly, the heat from the intense arc, and sparks from metal can burn your skin, hands, feet and legs. Masks and thick gloves and clothing should be used for shielding from heat. Professionals can handle a small hand-held torch withoutany gears and protectionfor cutting small surfaces. Tolerance to heat from the high temperature sparks generated by the arc increases by practice.
Secondly, there will be a lot of gases and metal vapors released from the cutting process. Protective helmets or masks can offer protection from inhaling these toxic and harmful gases.In addition, the bright, intense light from the arc, and the protection helmet or mask blur and block your vision of the workpiece itself.
Gas protection goggles or helmets with dark shades must be used for protection.As a beginner using the plasma cutter for the first time, you can expect to feel noise-induced headaches. Plasma cutters generate loud hissing noise when the compressed air gushes through the nozzle to generate plasma arc.
Plasma cutters at power levels above 250 amps are likely to produce 100db of noise that is above the threshold noise of 85db tolerated by human ear. Using ear plugs and muffsis a must to prevent suffering of noise-induced deafness.
Being a novice, it’s important to be extremely safe and suit yourself up with gears and protection such as helmets or masks, goggles,thick gloves, ear plugs, thick and heat-resistant clothing. Since it is difficult for the first time users to cut precisely or guide the plasma cutter seamlessly through the metal,one should notget disheartened and give-up. A few attempts and more practice is all you need to get better at plasma cutting.