ABRASIVE JET MACHINING AND STUDY OF PROCESS PARAMETERS

Abrasive Jet Machine Introduction Abrasive jet machining (AJM) is a non-traditional machining process that can machine material without generating heat and shock. Abrasive jet machining (AJM) is commonly used for Cutting, Cleaning, Drilling and Etching operation

Mechanism of AJM Fine particles are accelerated in gas stream . The particles are directed towards the focus of machining. As the particle impacts the surface, it causes a small fracture, and the gas stream carries both the abrasive particles and the fractured (wear) particles away.

Conventional Abrasive Jet Machine Compressor

Constructional Details Equipments involved in the construction of the “ Abrasive Jet Machine” are as follows COMPRESSOR 2. VIBRATOR 3. MIXING CHAMBER 4. NOZZLE 5. MACHINE TABLE 6. PRESSURE GAUGE & REGULATOR

Process Parameters 1.Carrier Gas : 2.Abrasive : The variables that influence the rate of metal removal are as follows : 1.Carrier Gas : Carbon dioxide, nitrogen & air. Air is most widely used 2.Abrasive : Aluminum oxide, Silicon carbide, Sodium bicarbonate etc. 3.Velocity of abrasive : The jet velocity is a function of nozzle pressure & design. The range of jet velocity is 150-300 m/min 4. Work Material : It is recommended for processing of brittle material 5. Nozzle Tip Distance (NTD) : It is the distance between the nozzle tip & work material.

Effect of Process Parameters on Machining a) Effect of Pressure of carrier gas on Material Removal Rate (MRR) S.No. Gas Pressure (Kgf/cm2) Material Removal Rate (MRR) (mg/min) 1 5 18 2 6 21 3 7 23 4 8 26 Table a)1 : Effect of Pressure on MRR 5 10 15 20 25 30 1 2 3 4 Pressure (Kgf/cm2) Material Removal Rate (MRR), mg/min Gas Pressure Kgf/cm2 Material Removal Rate Fig a)1 : Effect of Pressure on MRR Source : Previous Experiments conducted by M. Roopa Rani and S. Seshan

(b) Effect of Nozzle Tip Distance (NTD) on Diameter of Cut. S. No. Nozzle Tip Distance (NTD) (mm) Diameter of Cut 1 0.79 0.46 2 5.00 0.64 3 10.01 1.5 4 14.99 2.01 Table b1:Effect of Nozzle Tip Distance on Diameter of Cut. Fig b1:Shows the effect of Nozzle Tip Distance on Diameter of Cut. Source : Previous Experiments conducted by M. Roopa Rani and S. Seshan

Block Diagram of Fabricated Abrasive Jet Machine

Fabricated Abrasive Jet Machine Photograph of Fabricated Abrasive Jet Machine

Experimental Procedure: Glass was used as a test specimen, was cut into square and rectangular shape for machining on AJM. Specimens were cleaned using air jet and weighed on a sensitive scale, accurate to 0.001 gram . Each test sample was placed on the work chamber and machined by abrasive jet machine by varying various process parameters The machine work piece was then removed, cleaned and weighed again to determine the amount of material removed from the work piece. The size of hole at the top surface and bottom surface was measured and the results were tabulated.

Experimental Details: Experiment No:1- NTD Vs Diameter of Hole Observation – 1.1 Fig.1.1.1 Machined Work piece at Pressure = 5.5 kgf/cm2 Thickness of material = 4 mm

Nozzle Tip Distance NTD (mm) Bottom Surface Dia (mm) Observation Table Pressure = 5.5 Kgf/cm2 S.No. Nozzle Tip Distance NTD (mm) Top Surface Dia (mm) Bottom Surface Dia (mm) 1 6 7.05 4.51 2 12 8.72 5.05 3 15 11.21 5.33 4 18 11.65 6.65 Table1.1 Effect of Nozzle Tip Distance on Dia of Hole. Graph Dia Of Hole (mm) NTD (mm) Fig 1.1.2. Shows the graph of Diameter of Hole vs. Nozzle Tip Distance

Experiment No:1- NTD Vs Diameter of Hole Observation – 1.2 Fig 1.2.1 Machined Work piece at Pressure =6.5 kgf/cm2 Thickness of material = 4 mm

Nozzle Tip Distance NTD (mm) Observation Table Pressure = 6.5 Kgf/cm2 S.No. Nozzle Tip Distance NTD (mm) Top Surface Dia mm Bottom Surface Dia mm 1 6 7.55 4.55 2 12 9.75 5.65 3 15 11.15 5.91 4 18 11.75 6.05 Table1.2 Effect of Nozzle Tip Distance on Dia of Hole. Graph Dia Of Hole (mm) NTD (mm) Fig 1.2.2 Graph of Diameter of Hole vs. Nozzle Tip Distance

Experiment No:1- NTD Vs Diameter of Hole Observation – 1.3 Fig 1.3.1 Machined Work piece at Pressure = 8 kgf/cm2 Thickness of material = 4 mm

Nozzle Tip Distance NTD (mm) Observation Table Pressure = 8 Kgf/cm2 S.No. Nozzle Tip Distance NTD (mm) Top Surface Dia mm Bottom Surface Dia mm 1 6 7.72 5.05 2 12 9.95 5.75 3 15 11.45 5.96 4 18 11.81 6.75 Table1.3 Effect of Nozzle Tip Distance on Dia of Hole Graph Dia Of Hole (mm) NTD (mm) Fig1.3.2 Graph of Diameter of Hole vs. Nozzle Tip Distance

Experiment No:2- Pressure Vs Material Removal Rate (MRR) Observation - 2.1 Fig 2.1.1 Machined work piece for determination of MRR at Pr.=5.5 kgf/cm2 Pressure 5.5 kgf/cm2 Initial weight = 140.190 gm Final Weight = 140.150 gm Time = 20 sec Thickness = 8mm MRR = 120 mg/min Fig 2.1.2 Machined work piece for determination of MRR at Pr.=6.5 kgf/cm2 Pressure 6.5 kgf/cm2 Initial weight = 141.200 gm Final Weight = 141.130 gm Time = 20 sec Thickness = 8mm MRR = 210 mg/min Fig.2.1.3 Machined work piece for determination of MRR at Pr.=7.5 kgf/cm2 Pressure 7.5 kgf/cm2 Initial weight = 137.530 gm Final Weight = 137.370 gm Time = 20 sec Thickness = 8mm MRR = 400 mg/min

Observation Table Graph Table 2.1 Effect of Pressure on MRR S.No. Thickness = 8 mm, NTD = 12 mm Pressure kgf/cm2 Initial Weight (gm) Final Weight (gm) Time (sec) MRR (mg/min) 1 5.5 140.190 140.150 20 120 2 6.5 141.200 161.130 210 3 7.5 137.530 137.370 400 Table 2.1 Effect of Pressure on MRR Graph Fig.2.1.4 Graph of Pressure vs. MRR

Experiment No:2- Pressure Vs Material Removal Rate (MRR) Observation - 2.2 Fig. 2.2.1 Machined work piece for determination of MRR at Pr.=5.5 kgf/cm2 Pressure 5.5 kgf/cm2 Initial weight = 206.600gm Weight = 206.570 gm Time = 20 sec Thickness = 12 mm MRR = 90 mg/min Fig.2.2.2 Machined work piece for determination of MRR at Pr.=6.5 kgf/cm2 Pressure 6.5 kgf/cm2 Initial weight = 207.130gm Final Weight = 207.059 gm Time = 20 sec Thickness = 12mm MRR = 213 mg/min Fig 2.2.3 Machined work piece for determination of MRR at Pr.=7.5 kgf/cm2 Pressure 7.5 kgf/cm2 Initial weight = 201.750 gm Final Weight = 201.590 gm Time = 20 sec Thickness = 12mm MRR = 480mg/min

Observation Table Graph Table.2.2 Effect of Pressure on MRR S.No. Thickness = 12 mm, NTD = 12 mm Pressure kgf/cm2 Initial Weight (gm) Final Weight (gm) Time (sec) MRR (mg/min) 1 5.5 206.600 206.570 20 90 2 6.5 207.130 207.059 213 3 7.5 201.750 201.590 480 Table.2.2 Effect of Pressure on MRR Graph Fig.2.2.4 Graph of Pressure vs. MRR

Conclusion: From the experiment conducted it was observed that: Abrasive Jet Machine was fabricated with following specification: Diameter of nozzle = 3 mm Type of abrasive particle – aluminum oxide (AlO2) Pressure range – 5 to 8 kgf/cm2 Carrier gas used – Dry air From the experiment conducted it was observed that: 1. As Nozzle Tip Distance increases, the Top surface diameter and Bottom surface diameter increases 2. As the Pressure increases Material Removal Rate (MRR) also increases.

Scope of Future Work: In this fabricated abrasive jet unit experiment can be conducted : 1. By using different nozzle tip diameter. 2. By using different type of abrasive particles. 3. By using different sizes of abrasive particles. 4. By using different work material. 5. Also the abrasive jet machine can be improved by retrofitting, computer numerical control (CNC)

References M. Roopa Rani and S. Seshan “Abrasive Jet Machining-Process Variables and Current Application”Metals Materials and Process,1995 Vol.7 No.4,pp 279-290. P K Ray and Dr A K Paul, “Some Studies on Abrasive Jet Machining” Journal of the Institution of Engineers (India) vol 68 part PE 2 November 1987 Alok K.Verma, Cheng Y. Lin Associate Professor ,Engineering Technology Dept. Old Dominion University Norfolk, Virginia “Parametric Study of the Efficacy of Cutting Process in Abrasive Jet Machining (AJM)” P. C. Pandey & H.S. Shan ,” Modern Machining “ Tata McGraw-Hill Publishing Company , Edition :1980 Production Technology HMT Tata McGraw-Hill Publishing Company , Edition :1980 Maleev & Hartman “Machine Design “edited by O. P. Grover “ CBS Publishing & Distributor Amitabh Ghosh & Ashok Kumar Malik “Manufacturing Process “East –West Press Private Limited ,New Delhi, Edition 1995

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