What Is Water Jet Machining?

The machining process in which water jets are used to extract material from the workpiece is called water jet machinings (WJM).

In this process, water jets are used, which acts as a device in the form of a water saw. In this process, the water is raised very rapidly and further focused on the target workpiece.

At a high velocity and pressure, it is capable of using some abrasive particles mixed in water jet materials and some metals. In some processes, no abrasive is used, & these processes are known as pure water jet machining processes.

The water pressure used in this machinings process varies from 200 MPa to 400 MPa.  The pressure varies according to the workpiece from which the material is to be removed. This process is similar to the water erosion phenomenon that exists in nature.

It is mainly used to remove materials from soft and non-metallic workpieces such as plastics, rubber, glass, etc.  A high-velocity water jet is used in this process to remove materials from the workpiece.

The basic principles of this process are that the kinetic energy of the water jet must be converted into pressure energy so that it removes the material from the workpiece.

When the jet of water collides with a workpiece with kinetic energy, this kinetic energy will be converted into pressure energy. This pressurized energy will induce stress to the workpiece, and due to this, the tension material will start to move away from the workpiece.

Working Principle of Water Jet Machining:

It is based on the principles of water erosion. When a high-velocity jet of water hits the surface, the material is expelled.

Pure water jets are used to machine soft materials. But to cut hard materials, some abrasive particles are mixed with water for machining, and it is called AWJM (Abrasive Water Jet Machining).

Parts of Water Jet Machining:

#1. Reservoir

The reservoir is used to store water that will be used as a jet. From the reservoir, water is supplied for the jet-jet machining process.

#2. Pump

This pump will soak up the water from the reservoir, and it will transfer the water in intensity. The pumps are used to create pressure in water from 1500 to 4000 bar. To achieve this pressure, an electric motor of 50 to 100 hp is used.

#3. Intensifier

Intensifiers are used to increase the water jet pressure and to produce high-pressure liquid jets. This intensifier is connected to the accumulator. It accepts water under low pressure and exhales it through an accumulator at high pressure. It works through a hydraulic reciprocating mechanism.

#4. Accumulator

The accumulator is used to temporarily store water according to requirements. It is connected to the accumulator control valve. It maintains a continuous flow of high-pressure water and eliminates pressure fluctuations.

#5. Control Valves

This control valve controls the water pressure as well as the amount of water and directs it towards the flow regulator. This is where the pressure energies will be converted into kinetic energy.

#6. Flow Regulator

The flow of water arriving from the control valve is regulated using a flow regulator. After regulating the flow regulator, the water will pass through the nozzle, i.e., the high pressure of the water will be converted into high-velocity water.

#7. Nozzle

This nozzle will cover the pressure of the high-pressure jet in kinetic energy. The kinetic energy increases as the field decrease at the end of the nozzle. The jet of water from the nozzle is then directed towards the workpiece.

#8. Orifice

The water which is directed from the nozzles will come out from this orifice.

#9. High-Pressure Tube

High-pressure tubes are required for high-pressure water to flow. They are about 6 to 14 mm in diameter. It also allows flexible movement of the cuttings head.

#10. Catcher or Drain

Catchers or drains are used to collect water after cutting the workpiece. From here, water is sent for further purification or can be reflowed.

Abrasive Materials of Water Jet Machining:

The most commonly used abrasive particles in Abrasive Materials of Water Jet Machining are garnet & aluminium oxide. Sand (Si02) and glass beads are also used as abrasives. The function of abrasive particles is to increase the cutting efficiency of the water jet.

Working of Water Jet Machining:

First, the water is transferred at an intensity using a pump. The intensifier accepts the water under low pressure and then transfers it to the accumulator at a high pressure of about 3800 bar. The accumulator temporarily stores high-pressure water.

High-pressure water from the accumulator is transferred to a control valve that controls the direction of the water.

In the control valve, the water pressure energy is converted to kinetic energy, i.e., high-pressure water is converted to high-velocity water, and this high-velocity water is sent to the flow regulator.

The flow regulator controls and controls the flow rate of the water and directs it towards the nozzle. In the nozzle, the kinetic energy of the water increases significantly, and the nozzle produces high-velocity water.

Then the water comes out of the hole and is directed towards the workpiece. When the jet of water reaches the workpiece, the kinetic energy again changes to pressure energy, and the workpiece will be under full pressure.

This pressure due to the water jet will cause some fractures on the part of the workpiece where the water jet bike and some cracks will be introduced into the surface of the workpiece and as the water jet continuously strikes the surface of the workpiece for a long period of time, it will initially The crack will deepen and therefore the material will be removed from the workpiece.

The material that is extracted is carried away with water. After the removal of the material, the water that cuts the material is collected for further use.

The material in this water will contain parts of the chips which are cut using this process. This water will be sent for further purifications, or the water can be reassembled through the entire process of jet machining.

Advantages of Water Jet Machining:

Here, the different Advantages of water jet machining are as follows:

1. It has the ability to cut material without disturbing its original structure.
2. And this is because there is no heat-affected zone (HAZ). It is capable of producing complex & intricate cuts in material.
3. The work area remains clean and dust-free in this machining process.
4. Its operating and maintenance costs are low because it has no moving.
5. Thermal damage to the workpieces is negligible due to no heat generated. It is capable of cutting soft materials (WJM) such as rubber, plastic, or wood, as well as hard materials (AWJM) such as granite.
6. It is environmentally friendly because it does not create any pollution or toxic products.
7. It has greater machining accuracy. Inches tolerances of 0.005-inch order can be easily obtained.

Disadvantages of Water Jet Machining:

Here, the different Disadvantages of water jet machining are as follows:

1. It is used to cut soft materials. But AWJM can cut rigid materials of limited thickness.
2. Very thick material cannot be prepared by this process.
3. The initial cost of WJM is high.

Application of Water Jet Machining:

Here, the different Applications of water jet machining is as follows:

1. Water jet machinings are used in various industries such as mining, automotive, and aerospace to cut, shape, and streamline operations.
2. Materials that are usually mechanized by water jets (WJM or AWJM) are rubber, textiles, plastics, foam, leather, composites, tiles, stone glasses, food, metal/paper, and more.
3. WJM is mostly used for cutting soft and easy machined materials such as thin sheets and foil, wood, non-ferrous metal alloys, textiles, honeycomb, plastics, polymers, leather pieces, frozen, etc.
4. AWJM is commonly used to machine materials that are hard and tough to machine. It is used to machine steel, Al and other commercial materials, reinforced plastics, metal matrix, ceramic matrix composites, layered composites, stone, glass, etc., thick plates.
5. Apart from the machining process, high-pressure water jets are used in paint removal, surgery, cleaning, peeing, etc., to remove residual stresses.
6. AWJM can also be used for drilling, pocket milling, turning, and reaming.

FAQ: Water Jet Machining

What Is Water Jet Machining (Wjm)?

Water Jet Machining is a process in which high-velocity water jets are used to remove material from a workpiece. It can be used for cutting soft and non-metallic materials like plastics, rubber, and glass. When abrasive particles are added to the water, it is called Abrasive Water Jet Machining (AWJM), which is used to cut harder materials.

How Does Water Jet Machining Work?

WJM works on the principle of water erosion. High-velocity water jets, sometimes mixed with abrasive particles, are directed at the workpiece. The kinetic energy of the water jet is converted into pressure energy, which induces stress and removes material from the workpiece.

What Are the Main Components of a Water Jet Machining System?

The main components include:

1. Reservoir: Stores water for the jet.
2. Pump: Increases the water pressure.
3. Intensifier: Further increases the pressure of the water.
4. Accumulator: Temporarily stores high-pressure water.
5. Control Valves: Regulate water pressure and flow.
6. Flow Regulator: Controls the flow rate of water.
7. Nozzle: Converts pressure energy into kinetic energy.
8. Orifice: Directs the water jet towards the workpiece.
9. High-Pressure Tube: Transports high-pressure water.
10. Catcher or Drain: Collects water after cutting.

What Materials Can Be Machined Using Water Jet Machining?

WJM is suitable for soft and easy-to-machine materials like rubber, textiles, plastics, foam, leather, and food. AWJM can machine harder materials such as steel, aluminum, reinforced plastics, composites, stone, and glass.

What Are the Advantages of Water Jet Machining?

Advantages include:

1. No heat-affected zone (HAZ).
2. Ability to produce complex cuts.
3. Clean and dust-free work area.
4. Low operating and maintenance costs.
5. Negligible thermal damage to workpieces.
6. Environmentally friendly, as it does not produce pollution or toxic products.
7. High machining accuracy.

What Are the Disadvantages of Water Jet Machining?

Disadvantages include:

1. Limited to cutting soft materials (WJM).
2. AWJM can cut hard materials but only up to a limited thickness.
3. High initial cost of the machinery.
4. Not suitable for very thick materials.

What Are the Applications of Water Jet Machining?

WJM is used in various industries such as mining, automotive, aerospace, and manufacturing. Applications include cutting and shaping materials like rubber, textiles, plastics, foam, composites, and metals. AWJM is used for machining hard materials, drilling, pocket milling, turning, reaming, and even for non-machining purposes like paint removal, surgery, and cleaning.

What Are the Common Abrasive Materials Used in Abrasive Water Jet Machining?

The most commonly used abrasive materials are garnet and aluminum oxide. Other abrasives include sand (SiO2) and glass beads, which enhance the cutting efficiency of the water jet.