NOTES ON WATER JET MACHINING

Introduction :-

• Water jets alone (without abrasives) can be used for cutting. Thin jets of high pressure and high velocity have been used to cut materials such wood, coal, textiles, rocks, concrete, asbestos.
• The mechanism of material removal rate is by erosion. When high pressure water jet emerges of a nozzle, it attains a large kinetic energy.
• High velocity jet strikes the work piece, its kinetic energy is converted into pressure energy including high stresses in the work material.
• When the induced stress exceeds the ultimate shear stress of the material, rupture takes place.

Characteristics of Water Jet Machining (WJM):

• The pressures normally used in WJM are 1500 to 4000 MPa.
• Nozzle is made by sintered diamond and exit nozzle is about 0.05 to 0.35 mm.
• No moving parts in the system, so less operating and maintenance costs and safe process.
• No thermal damage to work and intricate shapes can be cut.
• The process is convenient for cutting soft and rubber like materials because teeth will get clogged in conventional methods.
  

Advantages of Water Jet Machining (WJM):

1. Water jet machining is a relatively fast process.
2. It prevents the formation of heat affected zones on the workpiece.
3. It automatically cleans the surface of the workpiece.
4. WJM has excellent precision. Tolerances of the order of ±0.005″ can be obtained.
5. It does not produce any hazardous gas.
6. It is eco-friendly.

Disadvantages of Water Jet Machining:

1. Only soft materials can be machined.
2. Very thick materials cannot be easily machined.
3. Initial investment is high.

Applications of Water Jet Machining:

1. Water jet machining is used to cut thin non-metallic sheets.
2. It is used to cut rubber, wood, ceramics and many other soft materials.
3. It is used for machining circuit boards.
4. It is used in food industry.