ABRASIVE WATER JETMACHINING

Non-conventional machining processes

• Electric Discharge Machining.• Chemical Machining.• Abrasives Water Jet Machining.• Electrochemical Machining.• Plasma Machining

HistoryDr. Franz in 1950’s first studied UHP water cutting for

forestry and wood cutting (pure WJ)1979 Dr. Mohamed Hashish added abrasive particles to

increase cutting force and ability to cut hard materials including steel, glass and concrete (abrasive WJ)

First commercial use was in automotive industry to cut glass in 1983

Soon after, adopted by aerospace industry for cutting high-strength materials like Inconel, stainless steel and titanium as well as composites like carbon fiber

Introduction Abrasive Waterjet Machining

• Water jet cutter, also known as a water jet or water jet , is an industrial tool capable of cutting a wide variety of materials using a very high-pressure jet of water, or a mixture of water and an abrasive substance

• JET : A rapid stream of liquid or gas forced out of a small opening.

• The term abrasive jet refers specifically to the use of a mixture of water and abrasive to cut hard materials such as metal or granite, while the terms pure water jet and water-only cutting refer to water jet cutting without the use of added abrasives, often used for softer materials such as wood or rubber.

Parameters Considered

• Abrasives• Medium i.e. Water• Nozzle (diameter ,material ,operating axis)

• Pressure

MACHINE SETUP

• Water reservoir • Pump • Intensifier pump• Nozzle• Nozzle controlling unit• Different valves

Water Reservoir And Pump

• Reservoir is nothing but water storage. From which the pump sucks the water

• There are two types of pumps are used the first one is common pump such as centrifugal pump. Another one is intensifier pump which ultra pressure generating pump.

Intensifier Pumps:•Intensifier pump utilize the ”intensification principle”Hydraulic oil is pressurized to a pressure ,say,3000psi.The oil pushes against the piston biscuit .•A plunger with face area of 20 times less than the biscuit pushes against the water.•Therefore, the 3,000psi oil pressure “intensified”20 times, yielding up to 60,000psi water pressure. The intensification principle varies the area component pressure equation to intensify, or increase, the pressure

Nozzle

• It is discharge point of water and abrasive mixture . the nozzle has small diameter for opening the diameter must not be more than 1,32mm.

• The discharging water has speed upto 4000kmph.nozzle has two inlet ports one for high pressure oil and another one for abrasives. There is separate mechanism to feed the nozzle that is it is not controlled by manually

• Only by the CNC it should be controlled.• The material of nozzle is Tungsten carbide or sffire.the

material should be hard and the particles must be tightly bonded with each other. The material should be chemically inactive

Nozzles

Typical Machining Centre

Working Process of abrasive water jet machining

• There are six main process in Abrasives water jet cutting:• Uses a high velocity stream of Ultra High Pressure Water 30,000–

90,000 psi (210–620 MPa) which is produced by an intensifier pump with possible abrasive particles suspended in the stream.

• Is used for machining a large array of materials, including heat-sensitive, delicate or very hard materials.

• Produces no heat damage to workpiece surface or edges.• Nozzles are typically made of sintered boride.• Produces a taper of less than 1 degree on most cuts, which can be

reduced or eliminated entirely by slowing down the cut process or tilting the jet.

• Distance of nozzle from workpiece affects the size of the kerf and the removal rate of material. Typical distance is .125 in (3.2 mm).

• Temperature is not as much of a factor

Multi Axis Cutting

• With recent advances in control and motion technology, 5-axis water jet cutting (abrasive and pure) has become a reality.

• Where the normal axes on a water jet are named Y (back/forth), X (left/right) and Z (up/down), a 5-axis system will typically add an A axis (angle from perpendicular) and C axes (rotation around the Z-axis).

• Depending on the cutting head, the maximum cutting angle for the A axis can be anywhere from 55, 60, or in some cases even 90 degrees from vertical.

• As such, 5-axis cutting opens up a wide range of applications that can be machined on a water jet cutting machine

Advantages of water jet machining • Cheaper than other processes.

• Cut virtually any material.• Cut thin stuff, or thick stuff.• Make all sorts of shapes with only one tool.• No heat generated. • Leaves a satin smooth finish, thus reducing secondary

operations.• Clean cutting process without gasses or oils.• Modern systems are now very easy to learn. Are very safe.• Machine stacks of thin parts all at once

• Unlike machining or grinding, waterjet cutting does not produce any dust or particles that are harmful if inhaled.

• The kerf width in waterjet cutting is very small, and very little material is wasted.

• Waterjet cutting can be easily used to produce prototype parts very efficiently. An operator can program the dimensions of the part into the control station, and the waterjet will cut the part out exactly as programmed. This is much faster and cheaper than drawing detailed prints of a part and then having a machinist cut the part out.

• Waterjets are much lighter than equivalent laser cutters, and when mounted on an automated robot. This reduces the problems of accelerating and decelerating the robot head, as well as taking less energy.

Disadvantages of abrasives water jet machining

• Abrasives are embedded in the work spaces that have soft surfaces as like elastomers or soft plastics.

• The tapering of the hole is hampered in its accuracy; this is due to the flares in abrasive jets.

• The stray cut is difficult to avoid.• Dust collection system is a basic need to prevent the atmospheric

pollution and health hazards.• The life of the nozzle is very limited upto 300hours approximately.• The abrasive powder is restricted be reused because the sharp

edges may worn out there is a chance to clog small particles in the nozzle.

• The short standoff distance may damage the nozzle when they are used for cutting.

• One of the main disadvantages of abrasive waterjet cutting is that a limited number of materials can be cut economically. While it is possible to cut tool steels, and other hard materials, the cutting rate has to be greatly reduced, and the time to cut a part can be very long. Because of this, waterjet cutting can be very costly.

• Another disadvantage is that very thick parts can not be cut with waterjet cutting and still hold dimensional accuracy. If the part is too thick, the jet may dissipate.

Applications And Materials Machined Using Abrasive Water Jet Machining

Application

• Paint removal • Cleaning • Cutting soft materials • Cutting frozen meat • Textile, Leather industry • Mass Immunization • Surgery • Peening • Cutting • Pocket Milling • Drilling • Turning • Nuclear Plant Dismantling

Materials• Steels • Non-ferrous alloys • Ti alloys, Ni- alloys • Polymers • Honeycombs • Metal Matrix Composite • Ceramic Matrix Composite • Concrete • Stone – Granite • Wood • Reinforced plastics • Metal Polymer Laminates • Glass Fibre Metal Laminates

Comparison Of AWJM With Other Non Conventional Methods

After plasma cutting

After AWJM After AWJM

After laser cutting

Future of AWJM

• Drilling wells• Drilling for oil• Radial tunnels

conclusionFrom all the point mentioned above we can conclude that the nonconventional machining process like AJM have bright industrial future .The AJM has shown that it can do things that other technologies simply cannot. From cutting whisper, thin details in stone, glass and metals; to rapid whole drilling of titanium; for cutting of food, to the killing of pathogens in beverages and dips, the waterjet has proven itself unique.

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