Improving technique and consumable life - Plasma Cutting part2
As much of a factor as the pilot arc duty time is in determining overall consumable life, proper torch manipulation is just as important, for both consumable life, and cleanliness of the cut. As already mentioned, having the torch close to the metal, ready to cut when the torch trigger is pulled is important. But also important, is starting the cut at or near the edge of a piece of metal when possible. If a part is drawn out or a template is used, the part to be cut should be placed on the metal to with at least one side near the edge or corner of the material. This will allow the torch arc to start just off the side of the metal, and the torch to be moved quickly into the full cut. This will allow a short “lead in” for the cut, so that little metal is wasted, and starts can be started, without the flame needing to cut through the entire length of metal first before starting the cut. Starting the torch in the middle of an intricate design, or cutting a hole in an object, will require a technique known as piercing. Piercing involves a steady hand and some for thought. Vertical piercing, where the torch is held 90 degrees over the cut, is the quickest way to destroying consumables and even the torch, especially on thick materials. CNC use cutters do in fact use this technique, but in reality, the capacity of a plasma cutter when used with a CNC table is cut in half because of this. Blowback from the spark and flame when the cut is started from straight overhead is redirected right back into the face of the consumable and torch. This blowback sends hot sparks, flame and material the wrong direction! For best use when piercing, identify the discard side of the cut. Angle the torch head back 30 degrees or so with the nozzle pointed toward the discard side cut, then start the arc. Rotate the torch head vertical as the arc begins to penetrate, and begin cutting. This will allow the arc to bounce the blowback away from the consumable face. Keep in mind the arc should be directed to the discarded side of the cut or you will cause damage to the piece you are trying to keep. This is a fairly rapid motion. If it takes too long to pierce, you may have reached the practical limit for piercing. The practical piercing capability of almost any plasma cutter is limited roughly to ½ it’s maximum clean cut capability.