Getting the Most Out of Your Plasma Cutter
Check out these winning tricks of the welding trade to improve your technique in plasma cutting:
Plasma arc cutting is an easy, fast and so handy that quite a few people keep their oxy-fuel setups switched off using it to just preheat their metal. In plasma arc cutting, a gas – which is normally air - combines with the electrical arc and forms a very high temperature plasma arc that runs from the electrode to the task piece (which can be any kind of material that conduct electricity) and carves through the metal.
When comparing plasma cutting to the mechanical or the oxy-fuel techniques of cutting, it certainly has many advantages. Plasma is much faster than oxy-fuel and cuts quicker – up to 75 ipm on 3/8 in steel. For instance, the Director of Ride Engineering for the Stratosphere Casino in Las Vegas, Patrick Brinckerhoff, carried out his own test for cutting speed before knocking down the high roller coaster on top of the Stratosphere Tower. Where a cut that had taken between seven to eight minutes with the oxy-fuel torch took just three minutes and ten seconds when the same cut was conducted with a plasma cutter!
In addition, he did not have any worries about transporting and safely storing acetylene with the plasma cutter. Some of the other advantages of the plasma cutter are absence of preheating time, the more compact and exact kerf (the width of the cut), the smaller region that is heat-affected and the capability to cut through any kind of metal that conducts electricity including brass aluminum, copper, galvanized steel and titanium.
Getting the best out of your plasma cutter begins with making sure that you have the proper equipment for what is required. Plasma cutters are rated depending on their capacity to cut. A rated capacity means the thickness of mild steel that can be cut precisely depending on a steady travel speed of 10 ipm and a severe cut means the maximum cut that a unit can accomplish in conditions that are ideal at travel speeds that are slower. So, a unit can be rated at 3/8” and have a maximum severe cut of 5/8 “on mild steel. The ratings can vary from one manufacturer to another.
Make time and read the owner’s manual for it gives vital information about getting the maximum from your plasma cutter and other safety precautions that have to be followed. Always keep your manual handy so that anyone can refer it when needed. The information given below is not a substitute to a through and through reading of your manual.
TAKE A TIP
Tips guide the plasma stream to the job piece. In order to increase its life, tips must be in agreement to the current settings that you plan to use. A lesser amp tip will have a smaller orifice to conserve a narrow plasma stream at lesser settings when used on thinner metal. If a 40-amp tip at 80-amp setting is used, it will distort the tip orifice and will have to be replaced. On the other hand, if a 80-amp tip on lesser settings is used, it will not guide the plasma stream well and will cause a wider kerf. To cut in corners and for using patterns, extended tips are to be used. Gouging tips are conceived to spread the plasma stream and get rid of a lot of material at one go which enables the arc to get rid of a huge quantity of material with just one pass.
While utilizing clean and dry air and is doing longer cuts, you can expect a continuous cutting time of about two hours. If the tip touches the work piece, it causes double arching and reduces the tip life as it gives way to another path for the current to trail along. But, if the tip is distanced too much away from the work piece, it will reduce the cutting capacity. So an ideal distance between the work piece and the tip would be 1/8”. Having a drag shield which joins to the torch holding the tip away from the work piece will make sure that a steady 1/8” in standoff is maintained, thus making it perfect for pattern cutting and for unsteady hands.
Prior to creating the first cut in your work piece, try a specimen cut on a similar kind of metal to ensure your travel speed and settings. If you are planning on a long cut, practice it beforehand so as to confirm that you have sufficient space for free movement and is able to hold the torch in a perpendicular position to your work piece. It is quite difficult to start and stop and still retain a clear cut.
For a more precise cutting, you can make use of your non-cutting hand as a pointer (check photo). This rest hand setting will give you the freedom of movement in every direction and at the same time help to keep a regular standoff and keep your hands steady. While poking on thin metal to begin a cut, the arc may punch through with very little or no backsplash. But if the metal is thick, you will have to begin by holding the torch at an angle of 45° so that the first burst of metal has a place to go. If this is not done, the metal will quickly wear away your consumables because of the splash back that is generated.
The owner’s manual will have a chart which compares material thickness to the travel speed in inches per minute. Normally, the quicker you work the cleaner will be your cut, especially when it is aluminum. For the thicker materials, the arc should exit the metal between 15° to 20° angle opposite to the route of travel. In case it is going straight down, it means that you are moving way too slowly and have unnecessary slag or a build-up of dross. If you are moving too fast, then molten metal will begin spraying back right into the tip. As the arc trails at an angle at the close of a cut, reduce the cutting aped and hold the torch angled into the cut through the final piece of metal.
Foe even more precision, you can clamp a horizontal edge on to the work piece so as to escort the torch. If repeatable cuts of similar shapes are to be made, a template can be created. Ensure that the guide is not inflammable. Both circle and straight guides are available to help you to ensure that the cutting is precise.