The Abrasive Jet Machining Engineering Essay

The scratchy thou Machining Engineering Essay rough yard machining is a kind of blasting surgical action and one of the most anticipant micro machining plow for ticklish and breakable veridicals like glasses and ceramics. solelyoy is removed ascribable to the corrosion ca utilise by impact of t either further testy outpouring. abrader commons railcar has precision X-Y axis vertebra of rotation slapdash mount to the trimting table and it has programmable Z axis with beak forum. agree to the proper design calculations we jakes select distinct components of scratchy fountain appliance.In this project, I develop the amaze victimisation opposite hotdog comportages like AUTO CAD and SOLID WORKS. Moreover I likewise rationalise the effect of several AJM operating parameters like tie-in distance, arise and type of testys on metal re action commit of AJM. I explain how we place maximize the efficiency of AJM by cont paradiddle their parameters. I n this model cargon has been taken that social function less construct component quite an than directly procuring them beca routine some ms we find less accuracy in fabricated component so performance of machine great deal be low. mental hospital of petulant pitchy MachiningMaterial removal accomplishes is a vox of manufacturing process and it bottomland be divided into two major groups. One is customary machining processes and a nonher is Non- conventional machining processes. Different types of conventional machining processes be move, Shaping, course sessioning, Slotting, Boring, etc. And the examples of Non Conventional Processes are pettish Jet Machining (AJM), Electro-Discharge Machining (EDM), Laser disperse Machining (lBM), Abrasive piss dust Jet Machining (AWJM) etc..Abrasive blue pitchy machining too called, Abrasive Micro blasting, it is a genuine removing process and actual is removed by a concent sum up steam of grating hints carried by high coerce throttle valve or aviation. A fine rasping particle strikes on pasture surface finished snob and the material is removed by erosion by the high fastness pettish particle.AJM is utilise of importly to cut materials that are very(prenominal)(prenominal) sensitive to heat damage and thin section of hard materials that chip easily and it is also used to cut intricate compels and holes which are to a greater extent difficult to work by other processes.Equipments of Abrasive Jet MachineCUsersVishalDesktoppart01.jpgA layout of Abrasive Jet Machining is shown in fig. Abrasive particles are fed from the hoper into the miscellany bedchamber. higher(prenominal) hale send off or gas (such as Carbon Di-oxide or Nitrogen) used as holder gas is supplied to the mixing chamber which containing irritable powder and vibrating at 50 c/s. with the help of compress regulator we cease control the gas break away and pressure. The high pressure air/gas entrains the abrasive particles and this motley comes out from wee beak at high upper. This stream of abrasive particles strikes on the surface of dress- human beings and cut the material.The abrasive stream is directed to the go go locations by nozzle, which whitethorn be manually directed or attach in some designed fixture for automatic operating theatre.For automatic accomplishment, cam drives, tracer bullet mechanism or pantographs used to automatically position either nozzle or belong piece.Abrasive Jet Machining MechanismCUsersVishalDesktopAjm line up up 3d.jpgIn this process kinetic energy of abrasive yard is strike on the surface of spirt piece wherefore it converts into pressure energy. If pressure energy is more than the yield strength or b stamp outable strength of piece of snip piece material thus material substantiates cut. key out of Components of AJMAbrasive Delivery constitution ( Including Hopper)Pressure RegulatorAir get through valveMixer schnozzleSuitable brass to hold the break pieceElements of Abrasive Jet Machine there are three main elements of AJMNozzleAbrasiveCarrier gasThe above mentioned three elements of AJM catchMaterial removal pose and accuracy of machiningNozzle wear tempoSurface roughnessGeometry of cutVariables in Abrasive Jet MachineThe process potty be easily controlled to vary the metal removal rate which Depends on pastime variables.Nozzle design ( mean underframe of nozzle such as circular, square)Distance betwixt the nozzle and work pieceInclination to the work surfaceType of abrasivesizing and shape of abrasiveFlow rate of abrasiveType of mail carrier gasesVelocity of abrasive fountain solve piece materialNozzle design Nozzle must be resistant under different conditions like pressure and kinetic energy of outpouring and common materials used for nozzle are tungsten carbide and synthetic sky-blue. Pressure losings at the end of nozzle should be low.Distance mingled with nozzle and work piece Standoff dista nce affect on material removal rate of AJM. Material removal rate is increase if we increase standoff distance up to certain limit and then fall gradually. miserable standoff distance gives go against penetration of abrasive particle into the work piece and grown standoff distance might brace flaring. successfully experiments show that effective standoff distance is 0.8mm.Types of abrasive Aluminum oxide is desirable abrasive in majority of diligence and silicon carbide abrasive also use in certain cases. Abrasive sizing also prominent factor in AJM. surmount results develop been obtained with a abrasive coat in the range of 10-50 m.Abrasive Flow Rate Maximum material removal rate is achieved with a flow rate at 8-18 g/m. Increase the flow rate above the normal range for a particular nozzle design results in lower stream velocity thus decrease the material removal rate. It is advisable to use unobjectionable flow rate to conserve abrasives and increase the nozzle life.Gr ain size Abrasives with menialer grain size deport high density which may cause chocking problem of nozzle. General grain size use in AJM is 10 to 50. Fine grains are used for polishing and de take awaying. unmannerly grain size cut faster and cut deeper also.Work piece material Abrasive resiny Machine is generally used for machining toffy material like ceramics and glass and effect of MRR is depends on hardness of material if hardness is high then MRR is low and vice versa.Advantages of Abrasive Jet MachineLow capital saluteLow creator manipulationAbility to cut intricate shapes in high hardness and toughness materialAbility to cut fragile and heat sensitive material without damage because no heat generated and overall forces are lowThe part produced is free of bursIt is flexible process from design point of viewTooling time is substantially reducedBoth faces of work piece offer be machined simultaneously.Disadvantages of Abrasive Jet MachineIt is slow process since metal removal rate is very slow.Larger floor space is needful complete operators are neededSharp corner domiciliatenot be produced gamy manufacturing costMaterial onerousness that can be machined is limitedAbrasive grains can stick into soft material so cleaning is call forHigh wear rate of nozzleThe process tends to pollute the environmentApplications of Abrasive Jet MachineRemoving flash and parting lines form the injection border machineDeburring and polishing plastic components like nylon and TeflonFrosting internal surface of glass tubesEtching marking on glass cylinderHigh quality surface can be easily producedGlue, paints can be removed effectively form paintings.Different Components of Abrasive Jet Machining raft upAbrasive Delivery SystemCNC Control SystemPumpNozzleDifferent Motion System of Nozzle catcher musical scaleAbrasive Delivery SystemModern abrasive sales pitch feed system do not need a vibratory feeders and other metering valves.For smooth and precision elud ing operation we need to have resolute and continuous abrasive flow rate.Now days we use hatchway metering system metering system which is very reliable and extremely repeatable.During machining line up up, once we measured the abrasive flow rate through opening we can enter that value in control guessr programmed and then no adjustment or further tuning of abrasive flow is ever be required.Bulk abrasive delivery system is mounted with the wheel and it is also easy to move and this kind of system is use compressed air to transport garnet from the bulk abrasive hopper to small hopper attached with the machine.Features can hold approximately 550lbs abrasive bay window be located 20 feet away from the Abrasive Jet machine. natural elevation and Width are of following 1320mm and 960mmCan handle minimum pressure 80 to 95 psi.How it worksAbrasive particles are stored into the hopper and abrasive container has one inlet and one outlet for air passage.The flow rate of abrasive is contr olled by rotational speed of aim.Due to rotation of cam, abrasive container gets vibration.The abrasive particle is delivered by rotation of cam and motor arrangement.CUsersVishalDesktophopper 3d.jpgCUsersVishalDesktopAbarsive hopper.jpgControl System for Abrasive Water green Machine around of abrasive peeing resinous machine equipped with the CNC control system.G decree programming is installed in CNC machine.But the limitations of the G code comptroller is that feed rate is held at constant speed and feed rate varies only for some regions like curves and corners.Another limitation of G code controller is that is used for rigid exquisite spears.Abrasive peeing jet machine is not a kind of rigid cutting tool. all time change the feed rate for curves and corner results in rasping cut.So by considering various parameters like parameters of nozzle and intricate shape of part and variable thickness of the work piece and materials going to cut help to assure the feed rate so t hat operation can be done smoothly.For that we have to prepare the control algorithm which compute the desired feed rate establish on the above parameters.By using G code we can convert this feed rate mechanism into a actual programming.This programming help to drive the servomotors and that controls the X Y motion and this way we can make part with more precision.PumpTwo type of pumps used in the Abrasive weewee jet system. One is Crankshaft pump which was used in old engineering science buy nowadays for high pressure cutting technology intensifier pump is used.In this hydraulic power pack system is a type of positive displacement pump.This system drives the intensifier.Hydraulic power pack system is controlled by microcomputers to set up the pressure etcElectric motor is used to drive the hydraulic pump and as the hydraulic swimming push the bighearted cylinder which generate the high force on small cylinder and this small cylinder pressurize the urine at the level which is proportional to the cross section area of larger cylinder to the small cylinder.NozzleHigh pressure wet flows into the nozzle and cutting head of nozzle which symbolize of an possibility and mixing chamber and an inaugurate where water jet mixed with the abrasive and form an abrasive water jet.Various motion of the nozzle is controlled by motion system crossways the material.CUsersVishalDesktopnozzle01.jpgHow water jet FormsTypical diameter of the nozzle is 6mm. High pressure water is then fed into the pipe which can race the water at 400 Mpa and consisting of different joints without any leakage amid them.When water passes through the orifice flow of water convert onto compress jet and orifice diameter is usually nigh 0.2 to 0.4mm.When water enters into the cutting head section pressure head of water is converted into velocity head.Velocity of water can be expressed as Vw = 2Pw / w.Where Pw is the pressure of water and w is density of the water.The orifice usually do of sapphire and life of the orifice is about 100-150 hours.From orifice narrow water jet passes through the small section vacuum is created in mixing chamber and that pulls abrasive particles and air into the mixing chamber.Abrasive particles are feed through the different techniques like Vibratory bowl or Belt feeder. miscellanea ChamberMixing tube is the section where abrasive particles mixed with the water jet.Focusing tube generally made of tungsten carbide because of its good abrasive resistance characteristics.Focusing tube has inner(a) diameter typical about 0.8 to 1.6mm and continuance of 50 t0 80 mm.To get the maximum accuracy we have to replace the mixing tube frequently. We can replace it when tolerance goes to a lower place the acceptable level.Numerical modeling of Mixing process can be described as of followIf we consider some energy losses at the water jet formation at the end of orifice then water jet velocity described as of following wayVw = (2Pw/ w)Where is Ve locity coefficient of the orifice.Volume flow rate of water can be expressed as followingQw = x Area of orifice x Vw= x /4 do x (2Pw/ w)= Cd x /4 do x (2Pw/ w)Where = co efficient of Vena ContractaCd = Discharge co efficient of orifice.So total power of the water jet can be expressed byPw = Qw x Pw= = Cd x /4 do x (2Pw/ w)Due to the loss amount in the mixing process both neural impulse and energy is not conserved. But assumed that no looses occur in momentum at initially.So ( x v) before = ( x v)After(airvair + wvw + ava)before = ( aivairr + wvw + ava)AfterAs we manage that air has very low density so momentum of air, before and afterwards are failureed.Consider one more assumption and is that after mixing abrasive particle has identical velocity of water and also neglect the momentum of abrasive then above equation can be expressed bywvw = ( w + a) vawSo vaw = (1/(1 + R) x vwWhere R is the onus factor = a/ wDuring mixing process momentum losses occur due to the clangoring between the abrasive particle and inner wall of focusing tube and collision between the abrasive particle and water jet so for time being consider momentum losses and then equation is described byV aw = x (1/(1 + R) x vwWhere is the momentum loss factor.Motion SystemMotion system can be designed in many ways consort to the motion of nozzle around a work piece.This mechanism proposes excellent operating conditions for the operator.CUsersVishalDesktop3dTable 3Imagetable1.jpgMaterials are hindranceed with the help of overhead exsert or fork lift truck to the tank.This mechanism is useful for 5 axis tables and also erects pretty much space to the vertical lean axis.This structure has restriction to the movement of nozzle that means movement of nozzle has limitation to twist and long distance between the table and work piece result in error due to the deflection of machine.In this type of mechanism, Nozzle is mounted to the Y axis carriage.CUsersVishalDesktop3dTable 3Imagetable 2.jpgY axis is moving barb and is mounted with the X axis.Back beam is place uprighted at the two ends.This mechanism is suitable for very large machine.CUsersVishalDesktop3dTable 3Imagetable 3.jpgIn above mechanism, nozzle is very close to the plane of work piece which background static and dynamic errors go operation is going on.This system is not suitable for manually material load up and this provide material loading is concern to the access of the tank.Cost approximation ( Bill of material)ItemCost per single itemNo of items requiredTotal cost analog motion engineer ways hsr30cm$3853$1155Precision en get by$1883$564Supporting Unit$ receipts3$432Frl unit air filter$481$48Diamond nozzle for long service life$9001$900Abrasive hopper with 90lb capacity$1321$132 another(prenominal) accessories$250$250Total$3481Material remotion rate Mechanism and Modeling in Abrasive Jet MachiningAs we discussed earlier, material removal rate takes place in abrasive jet machinin g because of the erosion of the work material and erosion take place due to the high impact of jet velocity strikes on the work piece. pastime assumption has been considered in mechanism of Material removal rate.Shapes of the abrasives are orbiculate and abrasive particles are rigid.Kinetic energy of the abrasive particles is fully used in removing material of the work piece.Erosion takes place in brickle material due to the brittle fracture and the quite a little of fracture is considered as hemispherical with the diameter which is equal to length of the indentation.CUsersVishalDesktopGeometry.jpgCUsersVishalDesktopPart2.jpgFrom the geometry of the erosion of materialDE = DF + EFEF = r = DE DFr = (dg/2) (dg/2 H) = -H + dg H dg Hr =Volume of the erosion of material is equal to the volume of hemispherical crater and is given byTB = 2/3= 2/3 x (dg H) 3/2As we know kinetic energy equation is given by mv so the kinetic energy ofAbrasive particle grit is given byK.Eg = mg V= /12 x dg g VWhere V = Velocity of Abrasive Particleg = Density of Abrasive Gritdg = Diameter of Single Abrasive Gritmg = Mass of Abrasive GritWhen Abrasive particle strikes on Work piece material, work piece will be subjected to maximum forces which cause the erosion of material which I indicated in figure by symbol H.Therefore work done is given byW = x F HImpact force F is give by F = Indentation Area x hardness of the materialW = x r H SAnd Work done is equal to Kinetic energy because we assumed that kinetic energy is fully utilise for material removal soW = Kinetic energy K.E x r H = = /12 x dg g VSo H = (dg g V)/ (6rS)= dg V (g/6S) 1/2Now material removal rate of brittle material can be expressed as of followingMrrB = TB x No. of strikes by abrasive grits per second N= TB x (ma/ /6 dg g)= (6TB ma/ dg g )Now Put the value of TB = 2/3 x (dg H) 3/2= 6 x (2/3 x (dg H) 3/2) x ma / ( dg g )= (4 ma g) x (H/dg) 3/2As we know that H = dg V (g/6S) 1/2So MrrB = (4ma/ g) x (dgV/dg) 3/2) x (g/6H) 3/4= (4maV) 3/2 / (63/4 x g1/4 x S 3/4)= (maV3/2) / (g1/4 x S3/4)Fabrication and multitude of Abrasive Jet MachineNozzleA standard length of cylindric rod typically made of Tungsten Carbide or synthetic Sapphire or MS was cut into the proper length groundd on the requirements by using power hack saw.By silicon chip process in Lathe machine we can reduced the diameter of cylindrical rod and bring up to 15mm.On same lathe machine we can make tip by Taper turning process by tapering one end of cylindrical rod.Then make a blind hole of 20mm on planner face of rod by using 12mm drill bit in drilling machine.Due to the tool tip angel, a shape of 118 degree formed at the end of blind hole.To get the 1mm of Tip of nozzle, we can use the 0.74mm drill bit in Drilling process.CamMild steel of 40mm diameter can be used as a raw material of Cam.Turning process is used to bring down the diameter up to 35mm.By using power hack saw we can get the required breadth (Approximate 25mm).T hen both cut faces can be machined in Milling Machine.Through hole can be made by 16mm Drill Bit in Drilling Machine.Abrasive ContainerAbrasive container usually made out of the hollow cylinder.On the both end of container two switch Iron plates were welded.On the top plate, two iron pipes fitted through the holes.There are two pipes in a system, one is inlet which is long-run and makes more agitation of abrasive particles and outlet pipe is shorter.Compressed air goes to the abrasive container through inlet pipe and mixed with the abrasive particles then mixture of Air and Abrasive forward to the nozzle to perform operationVibrator AssemblyAngel section is welded with the base plate by conjoin process.Induction motor is displace on the angle section which is replicate to the base plate.Induction motor is tightening with the nut and bolt with base plate.Cam is fixed with motor shaft and Abrasive container is connected to the rod and it is freely to rotate around the rod.CUsersV ishalDesktopVribator.jpgDesign data and Technical precondition of Various ComponentsX-Y TableX -Y table is prominent part of the abrasive water jet machine. Various fixturing arrangements have to be provided to hold the work piece opus operation is running.The travel of X-Y table has been decided base on the application.Table consists of two parts. One is upper plate and some other one is lower plate.Upper table travel in X direction and lower table travel in Y direction.establish the model of Omax 2626, table can travel 730mm x 660mm.Y axis of rotation is responsible for movement of work piece in Y direction.Other components of X-Y are of following. analog motion absorb wayRecalculating musket formal get alongSupporting unit for ball spangCouplingsNuts and boltsOther components as requiredLinear motion guide wayGeneral application of elongate motion guide is for the linear motion.Based on the different parameters like travel length, floor space requirement, type of equi pment being used, linear motion guide way is selected.With the help of different rollers which provide rolling elements between the rails and block we can get higher precision linear motion system.Frictional losses are reduced between the elements by restraint effects between the rails and block and it can withstand high load in any directions.Assembly of Linear motion top waySource Hiwin linear motion guide way catalog_G99TE13-0809CUsersVishalDesktopl m guide way.JPGL M Guide way with DimensionsStructure of linear motion guide wayAs shown in fig, each raw of balls have angle impinging 45 degree. Retainer plate has facility to hold the recalculating ball whap which guide linear motion guide way in directions.End plate is attached with the linear motion blocks which allow the balls to circulate.Side seal is placed between the row of balls and grease nipple is attached with the end plate.Linear motion guide way can achieve precise motion by setting up the section height smaller as much as possible ground on the requirements and also provide rigidity of the model.Compare to all others traditional slides, co efficient of friction of linear motion guide way is 1/50 th.Advantages of linear motion guide wayProvide high accuracy meagerly lubrications in traditional slides give errors in accuracy and in linear motion guide way frictional contact is rolling contact so it has little wear and therefore it has long life.Due to small frictional resistance a small driving force required to move the load and hence it provides high speed of motion.Provide meet loads capacity in all four directionBest advantage is the interchangeability of the parts.Ball ScrewBall screw assembly for linear motion guide way consists of screw and nuts.Helical togs or grooves provided between nuts and screws and balls are rotate between them.Ball succumb system provides the way to return the balls again that means when ball reach at the end of the nut it return through the return pipe.Ball nuts in ball screw assembly determine the fatigue failure in the system and ratios of number of threads in ball nut to the number of threads on ball screw decide the wear out.By considering the table length, calculation of X axis and Y axis ball screw length is determined.For our table our X axis ball screw length should be 730mm + 200 mm (Breadth for upper table) + 100mm allowances for below cover so it should be 1030mm.For Y axis table it should be 660mm + 200mm + 100mm so it should be 960mm.Based on the ball screw length, rail length is determined and which is 50mm larger than ball screw length.CUsersVishalDesktopball screw.JPGBall screw AssemblySupporting UnitsBall screw supported bearing are designed with the high bearing gracelessness equality to other conventional bearing.Two kinds of supports are available fixed end support unit and supported end support unit.In fixed end support unit can take all thrust by given work and in another support end support unit acts like usual b earing.Nut support is used to bolt the ball screw nut with the work load platform.Vertical motion ModuleVertical motion module comprise of all above components like L M guide way, squall holder , Ball screw assemble, supporting units, nozzle holder and nozzle etc.This assembly is used for adjustment of stand of distance between nozzle and work piece.CUsersVishalDesktopVerticle motion module.jpgFixture arrangement for work piece in Abrasive Jet MachineAs abrasive jet machine is used for various kind of applications that also result in various fixture arrangement of work piece based on the application.So not only one application can use for the applications.Usually Abrasive jet machine requires less fixturing equipment to get start the operation so combination of different components can be used for particular kind of work.Fixture is used to locate the work piece correctly and for quick loading to reduce the machining cycle time.To counteract undesirable movement or rotation of wor k piece while the work piece is under the process.When work piece is under the processes, high pressure of water and abrasive strikes on the work piece so it can move in sideways or lift up those results in errors.Most of abrasive jets are used to make monotonous parts or add some features to the existing parts. So for all kind of flat parts 3 parameters has to considered and which are X position , Y- position and angle of rotation with respect to X-Y point.Figure shows the fixture arrangement of work piece for flat parts using square and clamps.As shown in figure parts are lying on the slats and clamping is provided to hold on the side motion of work piece because slats do not provide better support to the work piece.A square plate is bolted with the tank. As shown in fig. Screws which are close to the work piece is a clamping screws and which are far from the work piece for the square to adjust the different thickness of material. This system is used to prevent the rotating moti on of slats.Comparison of Abrasive jet Machining process with other ProcessesAbrasive Jet machine Vs Laser Beam MachiningComparison with respect to the material can be cut Abrasive water jet can cut varieties of material with good conditions discriminate to optical maser beam machining. For refractory materials, laser beam machining has poor applicability whereas abrasive water jet has good applicability for same materials. expectant cost and abrasive water jet set up is very low examine to Laser machining.There is no heat produce in Abrasive water jet marching so it minimize the thermal distortion of material also minimize the secondary operation because it provides continuous or uniform smooth surface with little burr on the surface.As the thickness of the work piece increase, higher precision can be obtained by abrasive jet machine with the same or higher tolerance than laser.Abrasive water jets are safer compare to laser machining and abrasive jet nozzle is very innocent th an laser however life of nozzle is about 100-150 hours of operation.However there are some disadvantages associated with the abrasive water jet process while compare with the laser machining like tool wear is very low and power consumption also very low in laser machining as abrasive water jet has little high compare to laser.Abrasive water jet machine or Abrasive jet machine Vs. EDM.EDM has low applicability for the material like super alloys whereas abrasive water jet machining has good applicability of the same materials.Abrasive water jet machining has facility to make piercing in the parts by itself while EDM process has required pre drilled hole.There is no heat alter zone so this process eliminates secondary operations.Good capabilities to make large parts with economical cost.Rapid software programming which is very simple and less set up with fixturing make this machine considerable to buyers.It can work better in any kind of materials like conductive or non conductive.If the thickness of work piece is less than the 25mm or 1 inch, abrasive jet machine works five to eight times faster than the EDM but less precise as well.Abrasive water jets Vs PlasmaMaterial removal rate efficiency of plasma machining is very low compare to the abrasive water jet machining.Plasma machining is not preferable to refractory material while abrasive water jet machining applicable to wide range of materials.Abrasive water jet provides better edge finish than plasma machining process but plasma machining process is faster than the Abrasive water jet process.Abrasive water jet Vs. MillingMilling can be used for rapid drudgery if set up is already done and fully programmed whereas abrasive jet machining has rapid programming feature and if operator is well trained than set up do not required for the part.Minimal burring problem, less scrap, environmentally friendly, no oil soaked chips are the reasons of abrasive jet machining which replace milling process in machine shop s.