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ISSN: 2320-5407 Int. J. Adv. Res. 9(05), 607-616

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ISSN: 2320-5407 Int. J. Adv. Res. 9(05), 607-616 ISSN: 2320-5407 Int. J. Adv. Res. 9(05), 607-616 Journal Homepage: -www.journalijar.com Article DOI:10.21474/IJAR01/12883 DOI URL: http://dx.doi.org/10.21474/IJAR01/12883 RESEARCH ARTICLE ABRASIVE JET MACHINING AND OPTIMIZATION OF PROCESS PARAMETERS Sachin Vinay, Sachin Bhanwal and Sahil Yadav (Under Guidance Of Assistant Professor Mukesh Dadge), Dept. Of Mechanical Engineering, Delhi Technological University, Delhi, India. …………………………………………………………………………………………………….... Manuscript Info Abstract ……………………. ……………………………………………………………… Manuscript History Abrasive Jet Machining also known as micro-abrasive blasting or Received: 20 March 2021 pencil blasting is one of the mechanical energy based economical non- Final Accepted: 24 April 2021 traditional machining process for cutting, deburring, polishing, drilling, Published: May 2021 etching and cleaning of alloys, brittle metals and non-metallic materials due to its high degree of flexibility and low stress forces with less heat Key words:- Abrasive Jet Machining, FRL, S/N ratio, generation.In AJM process, fine abrasive grits (silicon carbides, Taguchi Method Aluminium oxides, Sodium bicarbonate, Boron Carbides, Crushed glass and Dolomite etc.) of typically ~0.025 mm are accelerated in a high velocity (150-300 m/s) jet of gas stream or air which is generated by converting pressure energy of carrier gas or air to its Kinetic energy and hence high velocity jet and nozzle directs abrasive jet in a controlled manner towards the work surface. Small fractures are created after impacting abrasive particles on the work surface. Copy Right, IJAR, 2021,. All rights reserved. …………………………………………………………………………………………………….... Introduction:- The abrasive jet machining process is advanced machining that has been employed in many manufacturing and processing industries for drilling and contouring, generating shallow and crevices, and deburring the components, cutting slots, etc. All of these operations can be performed at a faster speed and with a better surface finishing as per the requirement of the industries. This process uses a mixture of abrasive particles like Aluminum Oxide (Al2O3), Silicon Carbide (SiC), Sodium bicarbonate, Dolomite, or Glass beads, and these act as an eroding material and with a carrier like gas or air is used for machining. These mixtures of abrasive particles and air are achieved at very high pressure by a suitable arrangement. This pressurized mixture then flows through a tube and nozzle arrangement. When the pressurized mixture flows through the nozzle then, some pressure energy gets converted into kinetic energy or in a high-velocity jet. When the abrasive mixture at high pressure as well as high velocity strikes the surface of the workpiece the material is removed and takes place by the erosion of workpiece material. Components Of AJM: Air compressor Usually air is sucked directly from the atmosphere, it is firstdried and made dust free and then compressed to high pressure. Carrier gas pressure is kept between 15 – 20bar,based on the compressor capacity and jet velocityrequirement. Sometimes commercially pure nitrogen orcarbon di-oxide gas is also used to obtain better results forsome specific cases. FRL High pressure air is passed through a filter regulatorlubricating (FRL) unit to remove any suspended particlessuch as Corresponding Author:- Sachin Vinay 607 Address:- (Under Guidance of Assistant Professor Mukesh Dadge), Dept. Of Mechanical Engineering, Delhi Technological University, Delhi, India. ISSN: 2320-5407 Int. J. Adv. Res. 9(05), 607-616 dust or oil. Common compressor is fitted with a FRLunit to make the carrier gas dry and dust free. Presence ofsteam in compressed gas is highly undesirable as it cancoagulate and can cause agglomeration of abrasives during flow through pipelines. Pressure regulator and flow valve As the names suggest, compressed carrier gas pressure hasto be regulated properly as final jet velocity relies on it. Flowrate is also a crucial parameter that can af ect erosion rate(or MRR) via mixing ratio. Abrasive feeder and mixing chamber Fine grain abrasive powders initially maintained atatmospheric pressure at primary chamber are allowed to flow to secondary chamber and then to the mixing chamberunder the assistance of low amplitude vibration. Compressedcarrier gas is also passed through this mixing chamber andthus momentum transfer takes place between gas andabrasives. So abrasives gain momentum in terms of velocityand start flowing with carrier gas through the pipeline.During mixing, the predefined mixing ratio is maintained bythe amplitude and frequency of the vibration and pressure ofcompressed gas has no influence on it. Flow and pressureregulating valves are also employed here to control flowrate and pressure of gas-abrasive mixture. Nozzle Gas-abrasive mixture is directed towards the nozzle, whichconverts the hydraulic energy (pressure) into kinetic energyand thus a high velocity abrasive jet is obtained. The nozzleis kept at a particular distance over the work surface. Thus gap is termed as stand-of distance (SOD) and it is a paramount factor that governs machining accuracy.Inclination angle, the angle between work surface and jetaxis, is also controlled by orienting the nozzle. Moreover, thenozzle is mounted on a slider to impart necessary motions as per the required profile of cut. Working chamber A closed working chamber is indispensably necessary toavoid pollution. Workpiece, mounted by fixtures, is placedwithin this chamber. A vacuum cleaner is connected to theworking chamber for removing tiny suspended abrasives from air before discharging it to the atmosphere. Process Parameters In Abrasive Jet Machining: In any machining process or simply in a process, there exist some input variables called parameters or more precisely known as process parameters, which influence the output of the processes. In the abrasive jet machining, our main focus is to get higher material removal rate, better surface finishing, high accuracy, at a faster rate, etc. the principle of the AJM is based on the principle of erosion by high velocity jet abrasive jet. The variables that influences the erosion are: ● Material and density ● Average flow stress ● Ductility and brittleness the impinging particles ● Elasticity of the material ● Shape and geometry of impinging particles ● Impinging particle diameter or grit diameter ● Speed and angle of impact ● Distance between the nozzle mouth and work piece ● Mixing ratio ● Gas pressure During the machining process for a particular material some variable like material property no longer remains a variable. The variables that truly can be considered as parameters are abrasive velocity and angle of impact, distance between the nozzle mouth and the workpiece, mixing ratio, jet pressure and, shape and grit diameter, etc. Lets, take a look at some of them. Grid Diameter And The Shape Of Abrasive: The shape of the abrasive particle can be considered as spherical in shape with smaller spherical grits on the surface. However, the material removal rate (MMR) is higher in a case of irregular shaped abrasive particles than the spherical shaped abrasives. Smaller the grit size gives better surface finishing, generally used for the purpose of cleaning, polishing and grooving, but it gives a comparably lower material removal rate. Larger size of grit diameter gives rough surface finishing and generally used for cutting and peening, but it gives comparably higher material removal rate. 608 ISSN: 2320-5407 Int. J. Adv. Res. 9(05), 607-616 Nozzle Tip Distance Or Stand Off Distance: Nozzle Tip Distance (NTD) is the distance between the nozzle tip and the workpiece.Metal Removal Rate (MRR) increases with an increase in nozzle tip distance up to a certain limit then MRR remains constant to some extent and then MRR decreases with an increase in nozzle tip distance. Nozzle tip distance also influences the shape and diameter of the cut and for optimum performance, a nozzle tip distance of 0.25 to 0.75 mm is provided. Fig 1:- Nozzle tip distance. Abrasive Flow Rate: Abrasive Mass Flow Rate: The mass flow rate of the abrasive particles is a significant procedure parameter that impacts the metal removal rate in abrasive jet machining. In AJM, the mass flow rate of the gas (or air) in an abrasive jet is contrarily corresponding to the mass flow rate of the abrasive particles. Because of this reality, when persistently expanding the abrasive mass flow rate, Metal Removal Rate (MRR) first increments to an ideal worth (as a result of the increment in the number of rough particles hitting the workpiece) and afterward diminishes. However, if the blending ratio is steady then Metal Removal Rate (MRR) consistently increases with an increase in rough mass flow rate. Mixing Ratio: It determines the concentration of the abrasive particles in the abrasive jet and it can be defined as the ratio of the mass flow of the abrasive to the mass flow of the carrier gas. The concentration of the abrasives can be increased by simply increasing the percentage of the abrasives in the mixture. The increased percentages cause the increased in the number of strikes impact (micro cutting action) on the workpiece per unit time, hence there is an increase in the material removal rate. However, it is important to note that, continuous increase in the concentration of abrasive particles in the jet causes reduction in the MRR after a certain limit because further increase in abrasive lowers the jet velocity (as gas pressure is constant) and unavoidable collision (invites
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