This is a very good start type that is now used by several manufacturers. This start type uses air pressure supplied to the cutter to force a small piston or cartridge inside the torch head back to create a small start between the inside surface of the consumable, ionising the air, and creating a small plasma flame. Employing a HF circuit also can increase maintenance issues, as there are usually adjustable points that must be cleaned and readjusted from time to time. Inexpensive models will not have a pilot arc, and require touching the consumable to the work to start. It often interferes with surrounding electronic circuitry, and can even damage components.Īlso a special circuit is needed to create a Pilot arc. But, because of the high frequency high voltage power that is required generated to ionise the air, it has some drawbacks. Although it is older technology, it works well, and starts quickly. This start type is widely employed, and has been around the longest. Whilst other methods are used on some machines such as scratch start where physical contact with the material is requiredthey are unsuited for CNC applications. There are two main methods for arc initialisation for plasma cutters that are designed for CNC operation.
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This gas also assists the high velocity plasma gas in blowing the molten metal out of the cut allowing for a fast, slag - free cut. Zone A channels a secondary gas that cools the torch. Direct current DC straight polarity is used for plasma cutting, as shown in the illustration.
The stiff, constricted plasma arc is shown in Zone C. PlasmaC User Guideīy forcing the plasma gas and electric arc through a small orifice, the torch delivers a high concentration of heat to a small area. The main cutting arc then transfers to the workpiece through the column of plasma gas in Zone C. In a Plasma Cutting Torch a cool gas enters Zone B, where a pilot arc between the electrode and the torch tip heats and ionises the gas. Once the pilot arc has ionised the plasma gas, the superheated column of gas flows through the small orifice in the torch tip, which is focused on the metal to be cut. Inside the torch, the pilot arc starts in the gap between the negatively charged electrode and the positively charged tip. They consist of negative and positive sections separated by a center insulator. Plasma torches are similar in design to the automotive spark plug. While the goal of plasma arc cutting is the separation of the material, plasma arc gouging is used to remove metals to a controlled depth and width. The metal to be cut or removed is melted by the heat of the arc and then blown away. The plasma arc cutting and gouging processes use this plasma to transfer an electrical arc to the workpiece. Plasma is a fourth state of matter, an ionised gas which has been heated to an extremely high temperature and ionised so that it becomes electrically conductive.
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