Term
| 1. What is electrical plasma? |
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Definition
| Plasma created by an arc is an ionized gas that has both electrons and positive ions whose charges are nearly equal to each other. |
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Term
| 2. Approximately how many times hotter is the plasma arc than an unrestricted arc? |
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Definition
| 4 times (11,000x4=44,000) |
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Term
| 3. Why is the body on a manual plasma torch made from a special type of plastic? |
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Definition
| It has to withstand the high temperatures, ultraviolet light, and impact. |
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Term
| 4. How are the torch heads of a plasma torch cooled? |
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Definition
| By either air for low power or water for high powered torches. |
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Term
| 5. What three types of power switches are used on plasma torches? |
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Definition
| Thumb, foot (both manual), and automatic. |
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Term
| 6. Why are some copper parts plated? |
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Definition
| To help keep them spatter free. |
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Term
| 7. Why have copper/tungsten tips helped the plasma torch? |
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Definition
| The combination has helped remove the heat which allows the tip to last longer with better cuts. |
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Term
| 8. What provides the gap between the electrode tip and the nozzle tip? |
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Definition
| The nozzle insulator provides the critical gap spacing and the electrical separation of the parts. |
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Term
| 9. What are the advantages of a water shroud nozzle for plasma cutting? |
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Definition
| It is used to control the potential hazards of light, fumes, noise, or other pollutants produced by the process. |
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Term
| 10. How is water used to control power cable overheating? |
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Definition
| By putting the power cable inside the return water line, it allows a smaller cable to carry more current. |
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Term
| 11. What factors must be considered when selecting a material for plasma arc gas hoses? |
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Definition
| Heat resistant, ultraviolet light resistant plastic free of solvents and oils that might contaminate the weld large enough to carry the flow and rated for the pressure. |
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Term
| 12. Why must the cooling water be turned off when the plasma cutting torch is not being used? |
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Definition
| To prevent condensation from forming in the torch. |
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Term
| 13. What type of voltage is required for a plasma cutting torch? |
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Definition
| Constant current (dropping arc voltage) from 50 to 200 volts close circuit and 150 to 400 volts open circuit. |
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Term
| 14. A plasma arc torch that is operating with 90 volts (close circuit) and 25 amps is using how many watts of power? |
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Definition
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Term
| 15. Why do plasma cuts have little or no distortion? |
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Definition
| Because the high temperature allows for a higher travel rate which results in a lower heat input area. |
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Term
| 16. What has limited the upper cutting speed limits of the plasma arc cutting process? |
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Definition
| Machines were not capable of high enough speeds, of up to 300in/min, until the introduction of new machines and robotics. |
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Term
| 17. What metals can be commonly cut using PAC process? |
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Definition
| Copper, nickel alloys, high strength low alloy steels, aluminum, mild steel, stainless steel, and clad materials. |
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Term
| 18. What happens to torches not using drag nozzle tips if the standoff distance is not maintained? |
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Definition
| As the standoff distance changes, the kerf width and top edge of the plate can be adversely affected and touching the nozzle to the metal may result in instantly destroying the tip. |
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Term
| 19. What are two methods for establishing the plasma path to the metal being cut? |
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Definition
| High frequency alternating current and a pilot arc. |
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Term
| 20. List eight items that will affect the quality of a PAC kerf. |
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Definition
| Standoff distance, orifice diameter, power setting, travel speed, gas, electrode and nozzle tip, swirling of the plasma gas, water injection. |
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Term
| 21. List seven items that are affected by the choice of PAC gas or gases on the cut. |
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Definition
| Force, central concentration, heat content, kerf width, dross formation, top edge roundness, metal types. |
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Term
| 22. Describe stack cutting. |
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Definition
| It's the process of cutting through multiple layers of material at one time. |
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Term
| 23. How does PAC dross compare with OFC slag? |
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Definition
| Dross is composed of unoxidized base metal, oxides, nitrides, and slag is mostly oxidized base metal. |
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Term
| 24. Why must high-power PAC machines be used by a semiautomatic or automatic cutting system? |
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Definition
| The heat, light and other hazards make these machines unsafe for manual operation. |
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Term
| 25. What is the advantage of using a water table for PAC? |
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Definition
| The table reduces the noise level, controls the plasma light, traps the sparks, eliminates most of the fume hazard, and reduces distortion. |
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Term
| 26. How is plasma arc gouging performed? |
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Definition
| By holding the plasma torch at about 30 degree angle and traveling along the surface not allowing the groove to go through the plate. |
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