Water Jet Machines

How Water Jet Cutting Works

The working principle of water jet cutting machine and its advantages.

Water jet cutting as the name implies makes use high pressure water jets to cut the material. But is it possible cut hard material like steel with water? The answer is yes. To understand how this is possible let's learn about the working method of waterjet machines.

Water Jet Machine Working Principle

Water jets at ultra high pressure is capable of penetrating hard substances. You might have observed how water stream from pressure washer removes the dirt from your vehicle at the car wash center. In case of water jet machines the pressure exerted is much higher. In fact the pressure is at least 30 times more than the average pressure washers.
Typical water jet machines are equipped with waterjets with pressure between 30,000 and 55,000 PSI (pounds per square inch). The flow of high pressured water is channeled through a very narrow nozzle with constant pressure which enable waterjets to penetrate through the material and cut. Maintaining the spray coherent is the secret of water jet cutting machines.

Working Principle of Water Jet Cutters. (Image courtesy:Omax )

The term water jet only indicates flow of water with high pressure. The pure water jet is enough to cute plastic and other soft materials. However the pure waterjets alone can not penetrate through hard materials like steel. In such cases we need abrasive water jet machines.

Water Jet Cutting

Now let's see the actual water jet cutting process. The above figure explains the key principle by which the machine runs. At 50,000 PSI the water jet traveling through the narrow orifice will have a speed of 1,700 feet per second, more than twice the speed of sound.

In abrasive water jet machines there will be garnet abrasive mixed in water and now we have a very thin stream of water traveling very high speed that will rapidly erode most materials. Since the abrasive particles will result in erosion of work piece as well as the nozzle it is necessary to use the orifice made out of very hard material which can resist this erosion. Normally orifice jewel are made from Sapphire or Ruby. The movement of the machine is controlled by computer to precisely cut the desired geometry on the work piece.