Essay: 'PARAMETRIC EVALUATION OF JET CUTTING CNC MACHINE'

ABSTRACT
As per of our design we have classified the parts which are contained in our design. The jet cutting machine works on principle of cutting all types and different shaped material with optimum surface finish and material removal rate.
In water jet take ordinary tap water pressurize it to 60,000 psi (4000 bar) and force it through a very small orifice, using intensify technology.
Mix the water with garnet abrasive and you have a very thin stream of water travelling very fast that will rapidly erode most materials. The small orifice be of diameter of (0.2-0.4mm), which converts potential energy into kinetic energy.
Water Jet Abrasive cutting machine is a non-conventional machining process used for wide range of industries for defining variety of designs.
Waterjet
While using high-pressure water for erosion dates back as far as the mid-1800s with hydraulic mining, it was not until the 1930s that narrow jets of water started to appear as an industrial cutting device.
It was a necessity to develop more enhances technology for studying of fluid properties .
In 1933, the Paper Patents Company in Wisconsin developed a paper metering, cutting, and reeling machine that used a diagonally moving water jet nozzle to cut a horizontally moving sheet of continuous paper. These early applications were at a low pressure and restricted to soft materials like paper, but it was concluded that it has wide range of application in the field of non-conventional machine.
Waterjet technology evolved in the post-war era as researchers around the world searched for new methods of efficient cutting systems.
In 1956, Carl Johnson of Durox International in Luxembourg developed a method for cutting plastic shapes using a thin stream high-pressure waterjet, but those materials, like paper, were soft materials.
In 1958, Billie Schwacha of North American Aviation developed a system using ultra-high-pressure liquid to cut hard materials. This system used a 100,000 psi (690 MPa) pump to deliver a hypersonic liquid jet that could cut high strength alloys such as PH15-7-MO stainless steel.
Used as a honeycomb laminate on the Mach 3 North American XB-70 Valkyrie, this cutting method resulted in delaminating at high speed, requiring changes to the manufacturing process.
While not effective for the XB-70 project, the concept was valid and further research continued to evolve waterjet cutting. In 1962, Philip Rice of Union Carbide explored using a pulsing waterjet at up to 50,000 psi (345 MPa) to cut metals, stone, and other materials.
Research by S.J. Leach and G.L. Walker in the mid-1960s expanded on traditional coal waterjet cutting to determine ideal nozzle shape for high-pressure waterjet cutting of stone, and Norman Franz in the late 1960s focused on waterjet cutting of soft materials by dissolving long chain polymers in the water to improve the cohesiveness of the jet stream.
In the early 1970s, the desire to improve the durability of the waterjet nozzle led Ray Chadwick, Michael Kurko, and Joseph Corriveau of the Bendix Corporation to come up with the idea of using corundum crystal to form a waterjet orifice, while Norman Franz expanded on this and created a waterjet nozzle with an orifice as small as 0.002 inches (0.05 mm) that operated at pressures up to 70,000 psi (483 MPa).
John Olsen, along with George Hurlburt and Louis Kapcsandy at Flow Research (later Flow Industries), further improved the commercial potential of the waterjet by showing that treating the water beforehand could increase the operational life of the nozzle.
In the 1970s technology was developed in the USA that was capable of creating a 40,000 Bar pressure. Most of the waterjet mining growth after this involved combining a drill with the waterjet.
In 1972 Professor Norman Franz of Michigan worked with McCartney Manufacturing Company to install the first industrial waterjet cutter. The equipment was installed in Alton Boxboard.
Flow industries also began to market industrial waterjet cutting equipment. It was Flow Industries who added sand to a pressurized cleaning system to give metal a white finish. After this it was demonstrated that abrasive waterjet systems could cut through metal and ceramics. From here the waterjet cutting industry took off.
ABRASIVE WATER JET
While cutting with water is possible for soft materials, the addition of an abrasive turned the waterjet into a modern machining tool for all materials. This began in 1935 when the idea of adding an abrasive to the water stream was developed by Elmo Smith for the liquid abrasive blasting.
Smith’s design was further refined by Leslie Tirrell of the Hydroblast Corporation in 1937, resulting in a nozzle design that created a mix of high-pressure water and abrasive for the purpose of wet blasting.
Producing a commercially viable abrasive waterjet nozzle for precision cutting came next by Dr. Mohamed Hashish who invented and led an engineering research team at Flow Industries to develop the modern abrasive waterjet cutting technology.
Dr. Hashish, who also coined the new term “Abrasive Waterjet” AWJ, and his team continued to develop and improve the AWJ technology and its hardware for many applications which is now in over 50 industries worldwide.
A most critical development was creating a durable mixing tube that could withstand the power of the high-pressure AWJ, and it was Boride Products (now Kennametal) development of their ROCTEC line of ceramic tungsten carbide composite tubes that significantly increased the operational life of the AWJ nozzle.
Current work on AWJ nozzles is on micro abrasive waterjet so cutting with jets smaller than 0.015 inch in diameter can be commercialized
‘ Benefits of Abrasive Waterjet
‘ Preferred part finish over routers
‘ Much longer tool life ‘ up to 100 times
‘ No secondary operations required
‘ No material delamination
‘ No heat generation, so no heat affected zones (HAZ)
‘ No airborne dust
‘ Little or no cutting forces or vibrations
‘ Simple fixturing
‘ Higher feed rates/faster machining
‘ High speed
‘ High accuracy
‘ Robust construction
‘ Very few moving parts
‘ Ease of alignment
‘ Kinematic coupling for Side Fire
1.2 OVERVIEW
‘ Abrasive water jet machining (AWJM) process is one of the non-traditional machining processes that have been used extensively in various industry related applications.
‘ This technology is less sensitive to material properties as it does not cause chatter, has no thermal effects, impose minimal stresses on the workpiece, and has high machining versatility and high ‘exibility.
‘ Water Jet Machining (WJM) and Abrasive Water Jet Machining (AWJM) are two non-traditional or non-conventional machining processes. They belong to mechanical group of non-conventional processes like Ultrasonic Machining (USM) and Abrasive Jet Machining (AJM).
‘ In these processes (WJM and AJWM), the mechanical energy of water and abrasive phases are used to achieve material removal or machining. The general grouping of some of the typical non-traditional processes are shown below:
‘ Mechanical Processes
‘ USM
‘ AJM
‘ WJM and AWJM
1.3 CHARACTERISTICS
‘ There are six main process characteristics to waterjet cutting
‘ Uses a high velocity stream of abrasive particles suspended in a stream of ultra-high pressure water.
‘ 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.
‘ Distance of nozzle from workpiece affects the size of the kerf and the removal rate of material.
1.4 OBJECTIVE
1. To improve surface smoothness
2. To increase Material Removal Rate(MRR)
3. Validation of the results by conducting confirmation experiments.
4. Kerf taper ratio.
‘
1.5 ADVANTAGES
‘ It is flexible due to close intraction with the CAD / CAM programming system.
‘ No tool storage and tool manufacturing.
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