Today we will learn about water jet machining and abrasive water jet machining principle, working, equipment’s, application, advantages and disadvantages with its diagram. It is one of the most famous non-traditional machining process because it is environment friendly. It uses water jet working as a tool to cut the metal. It is same as abrasive jet machining except working medium is water. In this machining process a high speed steam of water jet impinge on the work piece which removes metal from contact surface by erosion. It is mostly used to machining soft materials. For machining hard materials like carbide, ceramic, etc. abrasive particles added in water steam which increases its machining quality. This process is known as abrasive water jet machining. It is mostly used in mining industries, aerospace industries for cutting required shape.
Water Jet and Abrasive Water Jet Machining:
This process works on basic principle of water erosion. In this process, a high speed well concentrated water jet is used to cut the metal. It uses kinetic energy of water particle to erode metal at contact surface. The jet speed is almost 600 m/s. It does not generate any environmental hazards. For cutting hard materials, abrasive particles are used in water jet These abrasive particles erode metal from contact surface.
|Diagram of Water Jet Machining|
In the water jet machining process a hydraulic pump is used to pump the water from storage tank for machining process. It is connected by
an electric motor of about 100 Horse power.
an electric motor of about 100 Horse power.
As the name implies, it is used to increase the water pressure for further process. Hydraulic intensifier accept water from pump at a small pressure about 4 bar. The water pressure at outlet of intensifier is about 3000-4000 bars.
Hydraulic accumulator is used when large amount of pressure energy is required for an instant. It used to eliminate pressure fluctuation It supplies fluid at high pressure when required.
Tubes are used to supply high pressure water to the nozzle for further cutting process. It increase the kinetic energy of fluid. It diameter is about 10-14 mm. It provide flexible movement and does not allow any significant loses.
Flow regulators are used to regulate the flow according to cutting requirement. For high cutting load, high pressurized water is supplied at high rate.
Abrasive particles are used in abrasive water jet machining for machine hard material. Generally Aluminium oxide, Silicon carbide etc. used as abrasive particles.
As we know, nozzles are used to convert pressure energy into kinetic energy. This nozzle convert high pressure of water into high velocity jet. This high speed water jet strikes at work surface which is used for machining. There is possibility of erosion at orifice of the nozzle due to high pressure water jet. Therefor high wear resistance material is used for nozzle. The size of nozzle is about 0.2 – 0.4 mm. If abrasive water jet machining is used, abrasive particles mixed in water stream before entering into nozzle.
Drain and Catcher
The drain and catcher system is used to remove debris and other machined particle form water. It separate metal particle from water and this water is further send to reservoir. It also used to reduce noise associate with WJM.
The working of water jet machining can be summarize as follow.
- First water is filled in water reservoir. It provides water for cutting operation.
- A pump sucks water from water reservoir and send it to intensifier.
- Intensifier increases the water pressure from 4 bar to 4000 bars. It sends water to accumulator which store some pressurize water.
- This high pressure water now sends through tubing system to nozzle. The water passes through flow regulator valve which regulate the flow.
- Now this high pressure water enters into nozzle. Nozzle converts some pressure energy of water into kinetic energy.
- A high speed high pressurize water jet is available at nozzle exit.
- This water jet send to strike at work surface. It erode metal from the contact surface. Thus metal removal take place.
This is whole working process of water jet machining.
- It is used in aerospace industries.
- Abrasive jet machining is used to cut hard metal like stainless steel, titanium, Inconel etc.
- It is used to machining or cutting reinforced plastic.
- Use to cut stone which reduce dust in environment.
- Used to machining PCB.
Advantages and Disadvantages:
- It does not change mechanical properties of work piece. It is useful for machining heat sensitive material.
- It is environment friendly because it does not form any dust particle and used water as cutting fluid.
- Good surface finish.
- No physical tool is require.
- It can cut both soft and hard material. For machining soft materials, water jet machining is used and for machining hard materials, abrasive water jet machining is used.
- It is ideal process for laser reflective materials where laser beam machining cannot be used.
- Lower cost of machining.
- It cannot used for machining material which degrade in presence of water.
- Low metal removal rate.
- High initial cost.
- Thick material cannot be machined easily.
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