Prof.Kamlesh H.Thakkar, Prof.Vipul M.Prajapati ,Prof.Shreyash A.Thakkar/ InternationalJournal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.1063-10661063 | P a g eA Machinability Study of Mild Steel using Abrasive Water JetMachining TechnologyProf.Kamlesh H.Thakkar*, Prof.Vipul M.Prajapati**,Prof.Shreyash A.Thakkar****(Department of Mechanical Engineering, SPCE Visnagar-384315)** (Department of Mechanical Engineering, SPCE Visnagar-384315)***(Department of Mechanical Engineering, SPCE Visnagar-384315)ABSTRACTAbrasive water jet machining is a nonconventional machining process in whichremoval of material takes place by impacterosion of high pressure, high velocity of waterand entrained high velocity of grit abrasives on awork piece. The objective of experimentalinvestigation is to conduct research of machiningparameters impact on Material removal rate andSurface roughness of work piece of Mild Steel(MS). The approach was based on Taguchi’smethod, analysis of variance and signal to noiseratio (SN Ratio) to optimize the Abrasive WaterJet Machining process parameters for effectivemachining and to predict the optimal choice foreach AWJM parameter such as Traverse speed,Abrasive flow rate, and Standoff distance. Thereis L9 orthogonal array used by varyingTransverse Seed, Abrasive flow rate, standoffdistance respectively and for each combinationwe have conducted three experiments and withthe help of Signal to Noise ratio we find out theoptimum results for AWJM. It was confirmedthat determined optimal combination of AWJMprocess parameters satisfy the real need formachining of Mild Steel (MS) in actual practice.Keywords – Abrasive Water Jet Machining,Garnet, Mild Steel1. INTRODUCTIONAbrasive Water Jet Machining is acceptedeffective technology for cutting various material asof its advantages over other non-conventionaltechniques such as No heat is generated in thecutting process, high machining versatility,minimum stresses on the work piece, high flexibilityand small cutting forces, the abrasives after cuttingcan be reused which allows for possible reduction ofthe cutting cost of the process, machining can beeasily automated. The process has some limitationsand drawbacks. It may generate loud noise and amessy working Environment, the machining is notapplicable for machining too thick pieces, limitednumber of materials can be cut economically, tapercutting is also a problem with water jet cutting invery thick materials.As in the case of every machining process, thequality of AWJC process is significantly affected bythe process tuning parameters. There are numerousassociated parameters in this technique, amongwhich water pressure, abrasive flow rate, jet traverserate, standoff distance and diameter of focusingnozzle are of great importance but preciselycontrollable . The main process quality measuresinclude attainable depth of cut, material removalrate and surface finish. Number of techniques forimproving kerf quality and surface finish has beenproposed.2. WORKING PRINCIPLEAbrasive water jet cutting is using highpressure water being forced through a small holeonto a concentrated area to cut materials. TheAbrasive water jet cutting machine starts with awater pump. The water pump pressurizes the waterand pumps it from a water tank or other watersupply to the nozzle.Fig.1: Abrasive Water Jet MachiningIf there is an abrasive added it is normallyadded at the nozzle which has shown in BelowFigure. A lot of water is forced through a smallnozzle. This creates water with a lot of pressure.This pressure makes the particles “accelerate” andhits a very small area on the piece being cut.All of the pressure onto the material beingcut makes the material crack. It creates very smallcracks and the pressure washes away the particles ofmaterial. The pressure eventually removes all of thematerial in the small area and this is the cut. Thematerial being cut is in a catch tank that is full of
Prof.Kamlesh H.Thakkar, Prof.Vipul M.Prajapati ,Prof.Shreyash A.Thakkar/ InternationalJournal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.1063-10661064 | P a g ewater and other debris. The water is normally raisedto just above the material to reduce the splash thatmay occur during cutting. All of the material that isbeing removed goes into the catch tank and can laterbe removed.2.1 ABRASIVE WATER JET CUTTINGMACHINE ELEMENT:Abrasive water jet cutting machines havefour basic elements: pumping system, abrasivefeed system, abrasive water jet nozzle andcatcher. The pumping system produces a high-velocitywater jet by pressurizing water up to as high as400 Mpa using a high-power motor. The waterflow rate can be as high as 3 gallons per minute. To mix the abrasives into this high-velocitywater jet, the abrasive feed system supplies acontrolled quantity of abrasives through a port. The abrasive water jet nozzle mixes abrasivesand water (in mixing tube) and forms a highvelocity water abrasive jet. Sapphire, tungstencarbide, or boron carbide can be used as thenozzle material. There are various kinds ofwater abrasive jet nozzles. Another element of the system is a catcher, forwhich two configurations are commonlyknown: a long narrow tube placed under thecutting point to capture the used jet with thehelp of obstructions placed alternately in theopposite direction and a deep water-filledsettling tank placed directly underneath thework piece in which the abrasive water jet diesout.3. EXPERIMENTAL WORK(A) Material:Mild steel is the most common form of steelbecause its price is relatively low while itprovides material properties that are acceptablefor many applications. It is often used whenlarge quantities of steel are needed, for exampleas structural steel. It is the most versatile formof steel. Mild steel – Grade 250 plates wereused as the specimens in this study.(B) Equipment:The equipment used for machining the sampleswas Water Jet Model: DWJ1525-FA which wasequipped with SL-V50 pressure pump with thedesigned pressure of 290 Mpa . The machine isequipped with a gravity feed type of abrasivehopper, an abrasive feeder system, apneumatically controlled valve and a workpiece table with dimension of 3000 mm x 3000mm. Sapphire orifice was used to transform thehigh-pressure water into a collimated jet, with acarbide nozzle to form an abrasive waterjet. setup of an abrasive water jet cutting process isThe shown in figure.2. Voltage:- 415 V Frequency:-50 Hz Phases:- 3 Power:- 3 kw Current:- 5.8 A Table size: 3000×3000 mm Travel: X Axis: 3000mm ,Y Axis:3000mm,Z Axis: 250mmFig: 2 - Setup of AWJM with Cutting table3.1 Design of Experiment (DOE)Design of experiments (DOE) is a powerfultool that can be used in a variety of experimentalsituations. DOE techniques enable designers todetermine simultaneously the individual andinteractive effects of many factors that could affectthe output results in any design. To achieve athorough cut it was required that the combinationsof the process variables give the jet enough energyto penetrate through the specimens.Most researchers identified Abrasive waterjet machining process parameters that greatly affectResponse parameter. The Process Parameter likeStandoff distance, impact angle, traverse rate,number of passes, abrasive material, abrasiveparticle size, abrasive shape, and abrasive mass flowrate, focusing tube diameter and focusing tubelength water pressure orifice diameter etc. In thispaper we have selected process parameter asTraverse rate (mm/min), Abrasive flow rate(gm/min) and Stand of distance (mm) to analyze itseffect onr MRR (gm/min) and Surface Roughness(𝛍m) in AWJM.3.2 CONTROL PARAMETER:-Factor A: Traverse speed (mm/min)Factor B: Abrasive flow rate (gm/min)Factor C: Stand of distance (mm)
Prof.Kamlesh H.Thakkar, Prof.Vipul M.Prajapati ,Prof.Shreyash A.Thakkar/ InternationalJournal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.1063-10661065 | P a g eFactors with level value:-Factors Level1Level2Level3Traversespeed(mm/min)350 300 250Abrasive flowrate(gm/min)250 300 350Stand ofdistance(mm)2 6 10Table: 1 -Factor with level value3.3 CONSTANT PARAMETERS:Fixed Parameter Set ValueAbrasive type GarnetAbrasive Size 80Mesh(0.180mm)Water flow rate 5.6 ltr/minOrifice diameter 0.25mmNozzle diameter 1 mmImpact angle 900Focusing tube diameter 0.8 mmWork piece thickness 10 mmTable: 2 -Fixed parameter3.4 L9 ORTHOGONAL ARRAY WITHTHREE FACTORS:-For each experiment, the machining parameterswere set to the pre-defined levels according totheorthogonal array.Sr.No.Traversespeed(mm/min)(A)Abrasive flowrate(gm/min)(B)Standofdistance(mm)(C)1 350 250 22 350 300 63 350 350 104 300 250 65 300 300 106 300 350 27 250 250 108 250 300 29 250 350 6Table:.3 - L9 Orthogonal array with ThreeFactors4. RESULT AND DISCUSSIONSSurface roughness is one of the mostimportant criteria, which help us determine howrough a workpiece material is machined. In all theinvestigations it was found that the machinedsurface is smoother near the jet entrance andgradually becomes rougher towards the jet exit. Thisis due to the fact that as the particles moves downthey loose their kinetic energy and their cuttingability deteriorates. By analyzing the experimentaldata of the selected material, it has been found thatthe optimum selection of the four basic parameters,i.e., water pressure, abrasive mass flow rate, nozzletraverse speed and nozzle standoff distance are veryimportant on controlling the process outputs such assurfaceTable: 4 –Result Tableroughness. The effect of each of these parameters isstudied while keeping the other parametersconsidered in this study as constant4.1 ANOVA ANALYSIS4.1.1 Main effect plot of MRRFig.3:- Main Effect plot for SN Ratio (MRR) v/sFactors Above plot shows the main effect plot of MRR atdifferent parameters like Traverse speed, Abrasiveflow rate and Stand of distance in Abrasive water jetmachining process of MS Main effects of MRR of each factor for various levelconditions are shown in above figure. According toabove figure the MRR increases with three majorparameter TS, AFR, and SOD. MRR is maximum inthe case of Traverse Speed (TS) at level 1 (350), inthe case of Abrasive flow Rate (MFR) at level 1(350), and in the case of Standoff distance (SOD)MRR will be maximum at level 1 (10). So theoptimal parameter setting for the MRR found TS(350) MFR (350) SOD (10).4.1.2 Main effect plot of SR:
Prof.Kamlesh H.Thakkar, Prof.Vipul M.Prajapati ,Prof.Shreyash A.Thakkar/ InternationalJournal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.1063-10661066 | P a g eFig.4: Main Effect plot for SN Ratios(Surface Roughness) V/s. Factors Above plot shows the main effect plot ofSurface Roughness at different parameters likeTraverse speed, Abrasive flow rate and Stand ofdistance in Abrasive water jet machining process ofMS.Above plot evaluates the main effects of each factorfor various level conditions. According to the abovefigure the surface Roughness decreases with threemajor parameter TS, AFR, and SOD. SR will beminimum in the case of Traverse Speed (TS) atlevel 1 (250), in the case of Abrasivw flow Rate(AFR) at level 1 (250), and in the case of Standoffdistance (SOD) at level 2(6). So the optimalparameter setting for minimum surface roughness isTS (250) MFR (250) SOD (6).4.2 OPTIMUM CONTROL PARAMETER LEVELThe ANOVA for desired response providethe significant factor. Therefore the optimal level ofa significant control factor is the level with thegreatest SN Ratio. Optimizing the output parameteris achieved by selecting the significant control factorat their optimum level. Control factor that are notsignificant can be set at any level.Response Traversespeed(mm/min)Abrasiveflow rate(gm/min)Stand ofdistance(mm)MRR 350 350 10SurfaceRoughness250 250 6Table: 5 -Optimum control parameter level5. CONCLUSIONIn this presents analysis of variousparameters and on the basis of experimental results,analysis of variance (ANOVA), and SN Ratio thefollowing conclusions can be drawn for effectivemachining of MILD STEEL (MS) by AWJMprocess as follows: Traverse Speed (TS) is the most significantfactor on MRR during AWJM. MeanwhileAbrasive Flow Rate and Standoff distance aresub significant in influencing. Therecommended parametric combination foroptimum material removal rate is TS (350)MFR (350) SOD (10). In case of surface Roughness Abrasive FlowRate is most significant control factor andhence the optimum recommended parametriccombination for optimum surface Roughness isTS (250) MFR (250) SOD (6) .REFERENCES1. M. Chithirai pon selvan and Dr. N. Mohanasundara raju “Analysis of surfaceroughness in abrasive waterjet cutting ofcast iron” International journal of science,environment and technology, vol. 1, no 3,2012, 174 – 182.2. F.L. Chen, E. Siores “The effect of cuttingjet variation on striation formation inabrasive water jet cutting” InternationalJournal of Machine Tools & Manufacture41 (2001) 1479–1486.3. Veselko Mutavgjic, Zoran Jurkovic“Experimental investigation of surfaceroughness obtained by abrasive water jetmachining” 15th InternationalResearch/Expert Conference “Trends in theDevelopment of Machinery and AssociatedTechnology” TMT 2011, Prague, CzechRepublic, 12-18 September 20114. Vinod B. Patel, Prof. V. A. Patel“Parametric analysis of Abrasives water jetmachining of EN8 Material” InternationalJournal of Engineering Research andApplications (IJERA), Vol. 2, Issue 3,May-Jun 2012.5. Leeladhar nagdeve, vedansh chaturvedi,jyoti vima “Parametric optimization ofabrasive water jet machining using taguchimethodology” international journal ofresearch in engineering & applied sciences,volume 2, issue 6 (june 2012).