We learnt a fair bit about plasma cutting basics in the first part of this series. In this second and final part of the series we try and take a deeper look at some of the basics of plasma cutting.
Shield gas further constricts and cools the nozzle. The shield gas is introduced into the plasma stream at the nozzle tip after the process of ionization.
Injection of Water
Injection of water essentially improves the quality of the cut and also helps to cool the nozzle. If the gas and the water swirl in the same direction and injected near the point of the nozzle where the arc exits, the arc is constricted further.
Pure gas is vital for the long life of the electrode and high-quality cut. If the gas is not pure then the arc will not be able to pierce thin materials even at low current levels.
Gases required for most applications are a start gas, cut gas and shield gas. Type and thickness of material to be cut, cutting quality, speeds and production costs are important factors to be considered when selecting gas combinations.
The plasma cutting process by water injection method needs filtered and deionized water. Dissolved minerals, suspended solids and other aspects influence the water conductivity and life of the nozzle and also increase the likelihood of interference. The rate of water flow should be adjusted as per the requirements mandated by the cutting machine. Extreme water flow results in an unstable arc and short life of the electrode. Water flow that is very low will cause inadequate cooling that will affect the life of the nozzle.
The material that is cut away during the process of plasma cutting is called kerf and is affected by three factors: cutting speed, cutting amperage and standoff (distance between the torch and the workpiece after piercing).
Arc voltage depends on variables such as current, standoff, orifice size of the nozzle, flow rate of the cutting gas, flow rate of the cutting water (if water is being used) and cutting speed.
This concludes the second part of the series. As you can see there are various factors that must be considered and understood before buying a plasma cutting system and using it at your workplace, in order to get optimum results from your plasma cutting machine.