Water jet cutting
Water jet cutting uses an abrasive powder introduced into a very high - pressure and velocity water jet and is capable of cutting both metallic and non-metallic materials essentially by a process of erosion. Water velocity is in the region of 2500 km/h (1600 mph) and water pressure between 2000 bar (30000psi) and 4000 bar (60000 psi). One of the most important uses of water jet cutting is the roughing out of parts prior to finish machining. The great advantage that water jet cutting has over the laser or plasma-arc is that no heat is used in the process. There are therefore no heat affected zones and no thermal distortion. Parts can be cut very accurately and closely nested, resulting in material savings. Cut part tolerances are very small, simplifying the task of fitting up for welding.
Although aluminium up to 450 mm in thickness can be cut using the process, the limitations with water jet cutting are the cutting speed, which may be only a quarter the speed of a laser cut component, particularly in thin sections. The other limitation is the bevel or taper of the cut face which may be twice that of laser cutting, some 25% of the nozzle diameter or around 0.2 mm at the optimum cutting speed. The bevel can be reduced by slowing the cutting speed with the penalty of an increased cost.