SEMINAR REPORT On ABRASIVE JET MACHINING submitted to Veer Surendra Sai University of Technology in partial fulfillment of the requirements for the award of the degree of Bachelor of Technology In Production Engineering Submitted by :SUBHASISH HARSH-1802111055 Facilitator: Dr. Sudhansu Ranjan Das DEPARTMENT OF PRODUCTION ENGINEERING VEER SURENDRA SAI UNIVERSITY OF TECHNOLOGY BURLA ODISHA APRIL 2022 व ीी स ीर ीी ीीी स ीी ीीीीीीीीग ीीी ग व ीीी ग व ीीीील य ब ील ीी, ीीीश ी उ ततप तद न अ भतततततभ ततत भ तततत Veer Surendra Sai University of Technology Burla, Odisha Department of Production Engineering P.O: Engineering College Burla (Siddhi Vihar), Dist: Sambalpur, Odisha – 768018, India. Website : www.vssut.ac.in, E-mail: head_prod@vssut.ac.in CERTIFICATE This is to certify that the seminar report entitled “ABRASIVE JET MACHINING” submitted by Subhasish Harsh (1802111055), in the partial fulfillment of the requirement for the award of the degree of Bachelor of Technology from the Department of Production Engineering, Veer Surendra Sai University of Technology, is a record of candidate’s own work carried out by him. The matter embodied in this report has not been submitted in part or full to any other university or institute for the award of any degree. This is to certify that the above statement made by the candidate is correct to the best of my knowledge. Approved by: Dr. Sudhansu Ranjan Das (Facilitator) Dr. Kamal Pal (Head Of Dept.) Associate Professor DoPE, VSSUT Burla Associate Professor DoPE, VSSUT Burla DECLARATION OF ACADEMIC INTEGRITY I, Subhasish Harsh (1802111055) students of B. Tech (Semester-VIII) of Veer Surendra Sai University of Technology Burla, Odisha hereby declare that the seminar report entitled “Abrasive Jet Machining” is an original work and data provided in the study is authentic to the best of my knowledge. This report has not been submitted to any other Institute for the award of any other degree. Date: 05/04/2022 Place: Burla Subhasish Harsh Roll no.- 1802111055 ACKNOWLEDGEMENT It is my pleasure to be indebted to various people, who directly or indirectly contributed in the development of this work and who influenced my thinking, behavior and acts during the course of study. I am thankful to Dr. Sudhansu Ranjan Das for his support, cooperation, and motivation provided to me during the seminar for constant inspiration, presence and blessings. I also extent my sincere appreciation to the faculties of my department who provided their valuable suggestions and precious time in accomplishing my Seminar report. Lastly, I would like to thank the almighty and my parents for their moral support and my friends with whom I have shared our day-to-day experience and received lots of suggestions about my quality of work. Subhasish Harsh (180211055) Table of Contents SL. NO. TOPICS PAGE NO. 1 Abrasive jet machining: Abstract 6 2 Introduction 6-7 3 Equipment 7-8 4 Operating Principle 8-9 5 Mechanism of material removal 6 Abrasives 9-10 7 Process Parameter Influence MRR 10-13 8 Benefits 13-14 9 Limitations 14 10 Application 14-15 11 Conclusion 15 12 Reference 16 9 ABSTRACT:Abrasive jet machining is one of the mechanical type non-conventional machining. This process used to cut hard and brittle material like glass, mica, germanium etc. Here the operating elements are carrier gas, nozzle and abrasives. Here material removal takes place by an impact erosion through a concentrated stream of grit abrasives in high velocity gas stream. The equipment consists of gas supply unit, pressure regulator, filter, mixing chamber, dust collecting device according with the work-holding device. Here carrier gas comes out from compressor needs to be dry and filtered for removal of unnecessary contamination. Then abrasive grits are allowed to flow with the gas stream where mixing ratio is controlled by vibrator. Then the gas and abrasive mixture enters into the machining chamber and comes out from nozzle hence machining will done. Here the accuracy of cut area depends upon the standoff distance from work piece. AJM has become a useful technique for micro machining. It has various distinct advantages over the other non-traditional cutting methods, which are high machining versatility, minimum stresses on the substrate. This paper deals with several experiments that have been conducted by many researchers to assess the influence of abrasive jet machining (AJM) process parameters such as type of abrasive Particle , Abrasive Particle size, Jet pressure Nozzle tip distance. Various experiments were conducted to assess the influence of abrasive jet machine. INTRODUCTION:In Non-traditional machining process different forms of energies are directly supplied to the work piece for material removal. Here material removal takes place without chip formation, if chip formation takes place in some cases then that would be of microscopic size. Most of the non-traditional machining do not require any physical contact between tool and work piece. These processes are not affected by hardness, toughness or brittleness of material and can produce any intricate shape on any material by suitable control over various process parameters of the process. Here the basic mechanisms for material removal are impact erosion, ionic dissolution, and vaporization while source of immediate energy required for material removal are hydrostatic pressure, high current density, high voltage, ionized material etc. These can be classified according to the source of energy used to generate such a machining action: mechanical, thermal, chemical and electrochemical. Abrasive Jet Machining (AJM), or in other words Abrasive jet cutting, is a mechanically advanced unconventional machining process where abrasives having a very high velocity is used to erode away small portions of materials from the work piece surface. AJM was initially used for cutting soft materials, in early 70s. Softer materials like wood, plastic and rubber were cut using this technique. It does not encounter any vibration problems. However, in order to machine hard materials like metals and granite, another machining process called Abrasive Jet Machining (AJM) was developed. ABRASIVE JET MACHINING: In AJM, the material removal takes place due to impingement of the fine abrasive particles. It can be used to cut hard and brittle material such as germanium, silicon, mica, glass and ceramic in a high velocity cutting and deburring action. This process is smooth and free from vibration. EQUIPMENT:The machine tool of abrasive jet machine consists of gas supply unit, filter, pressure gauge, mixing chamber, nozzle and dust collecting chamber along with the work holding device. Gas supply : The filtered gas, supplied under a pressure of 2 to 8 kgf/cm to the mixing chamber containing the abrasive powder and vibrating at 50 Hz entrains the abrasive particles and is then passed into a connecting hose. This abrasive and gas mixture emerges from a small nozzle mounted on a fixture at a high velocity ranging from 150 to 300 m/min. Filter: The filter is used to clean the fuel supply so that dirt or other impurities do not hamper the progress of the process. Pressure gauge: It is used to control the pressure of the compressed used in the abrasive jet machining. As the pressure decides the depth of cutting and the amount of force required for cutting. Mixing Chamber: In the mixing chamber, abrasive powder is being fed and with the help of a vibrator amount of abrasives can be controlled. So that the abrasives and the gases will be mixed thoroughly in the mixing chamber. Nozzle: The nozzle is used to increase the velocity of the fine abrasive jet slurry at the expense of the pressure, as we know if we decrease the pressure, the velocity will increase. The material of the nozzle should be able to withstand corrosion. The nozzle is made of either circular or rectangular cross-sections and the head can be straight or at a right angle. Nozzle material: For aluminium oxide (Al2O3) abrasive: Tungsten Carbide (WC) nozzle For Silicon Carbide (SiC) abrasive: sapphire nozzle Where hardness of tungsten carbide (WC) < Hardness of sapphire Life of nozzle varies between (12hrs-30hrs) and standoff distance varies between (0.25-7.5) mm. Machining Chamber: It is well closed so that concentration of abrasive particles around the working chamber does not reach to the harmful limits. Machining chamber is equipped with vacuum dust collector. Special consideration should be given to dust collection system if the toxic material (like beryllium) are being machined. OPERATING PRINCIPLE Here the material removal rate is governed by mass flow rate and velocity of the abrasive particles uniquely related to gas mass flow rate. The jet coming of the nozzle remains straight for some time then flares out, so the accuracy of the cut area depends upon the nozzle tip distance from the work piece. Here carrier gas from nozzle needs to be dried for removal of water/ oil vapor. Then filtering is done for removal of unnecessary contamination. The abrasive is allowed to flow into the gas stream where the mixing ratio is generally controlled by vibrator. The mass flow rate of abrasive entering into the mixing chamber depends upon amplitude and frequency of vibration of shaker and hence the sieve. Then the particle and gas mixture comes out of the nozzle inside the machining chamber of the machine tool unit. Here feed motion can be given either to the work-holding device or to nozzle. Here operating elements are carrier gas, abrasive and nozzle. The variables that affect the cutting phenomena are abrasive, carrier gas and nozzle, where in abrasive we have to consider its composition, strength, shape, size and mass flow rate.Simillarly in carrier gas: composition, pressure and velocity and for nozzle: geometry, composition and standoff distance respectively. MECHANISM OF MATERIAL REMOVAL: Here material removal takes place by impact erosion through the action of a concentrated high velocity stream of the grit abrasive in a high velocity gas stream. So the kinetic energy of the particle is utilized to cause micro indentation in the work material and the material removal is a major of indentation. ABRASIVES: Aluminum oxide (Al2O3 ) ,Silicon carbide (SiC) ,Glass beads, crushed glass and sodium bicarbonate are some of abrasives used in AJM. Selection of abrasives depends on MRR, type of work material, machining accuracy. Silicon carbide is used as a loose or solid abrasive material in a variety of applications Due to its high abrasion resistance and relatively low cost. Synthetic silicon carbide is the hardest abrasive blasting media in use today. Silicon carbide offers the benefit of an extremely fast cutting speed, which, when combined with its hardness, allows for much shorter blasting times. This results in a lower per-hour cost than most other abrasive media types. The abrasive particles are considered rigid and spherical bodies of diameter equal to the average grit size. These abrasives are used in AJM are non-circulating as their effectiveness reduce a lot within one cycle. Aluminium oxide (Al2O3) Silicon carbide (SiC) PROCESS PARAMETER INFLUENCES (MRR): Parameters of Abrasive Jet Machining (AJM) are factors that influence its Metal Removal Rate (MRR). In a machining process, Metal Removal Rate (MRR) is the volume of metal removed from a given work piece in unit time. The following are some of the important process parameters of abrasive jet machining: 1. Abrasive mass flow rate 2. Nozzle tip distance 3. Gas Pressure 4. Velocity of abrasive particles 5. Mixing ratio 6. Abrasive grain size Abrasive mass flow rate: Mass flow rate of the abrasive particles is a major process parameter that influences the metal removal rate in abrasive jet machining. In AJM mass flow rate of the gas (or air) in abrasive jet is inversely proportional to the mass flow rate of the abrasive particles. Use to this fact, when continuously increasing the abrasive mass flow rate, Metal Removal Rate (MRR) first increases to an optimum value (because of increase in number of abrasive particles hitting the work piece) and then decreases. However, if the mixing ratio is kept constant, Metal Removal Rate (MRR) uniformly increases with increase in abrasive mass flow rate. Nozzle tip distance: Nozzle Tip Distance (NTD) is the gap provided between the nozzle tip and the work piece. As the standoff distance is increased, the initially MRR increases due to increase in velocity as the abrasives get enough time to gain velocity before collision. But as the standoff distance further increases then atmospheric resistance checks on the kinetic energy of the abrasives and through the velocity and hence kinetic energy tend to increase the atmospheric drag keeps checking on and the impact energy remains almost constant and hence a constant MRR is maintained for increasing standoff distance. After which the atmospheric resistance start to dominate the kinetic energy of abrasive and hence further increase in standoff distance results in decreasing MRR. Gas pressure: Gas pressure has a direct impact on metal removal rate. In abrasive jet, machining, metal removal rate is directly proportional to air or gas pressure. Velocity of abrasive particles: Whenever the velocity of abrasive particles is increased, the speed at which the abrasive particles hit the work piece is increased. Because of this reason, in abrasive jet machining, metal removal rate increases with increase in velocity of abrasive particles. Here velocity effects are more predominant than mass flow rate on material removal rate. Under lower velocity condition ductile material show lower material removal, rate for an angle of impingement 90 degree than brittle materials. However, at certain velocity U*, both material may exhibit similar property for impact erosion rate and above this velocity; ductile materials may erode very fast. Mixing ratio: Mixing ratio is a ratio that determines the quality of the air-abrasive mixture in Abrasive Jet Machining (AJM). It is the ratio between the mass flow rate of abrasive particles and the mass flow rate of air (or gas). When mixing ratio is increased continuously, metal removal rate first increases to some extent and then decreases. Abrasive grain size: Size of the abrasive particle determines the speed at which metal is removed. If smooth and fine surface finish is to be obtained, abrasive particle with small grain size is used. If metal has to be removed rapidly, abrasive particle with large grain size is used. BENEFITS: 1. This method facilitates to machine the complex holes and intricate cavities of harder materials of desired shape. 2. The fragile metals, which are very difficult to machine in the conventional machining process, are easily machined by this process with better accuracy. 3. Machining can be performed easily for brittle type of materials of thin sections. 4. Capital investment if very low. 5. No direct contact occurs between the work piece and the tool. 6. Heat generated in this process is very less. LIMITATION: Less capacity of the process due to low Material removal rate. While machining soft material abrasive gets embedded which will decrease its surface finish. The accuracy of cutting is disturbed by the tapering of the hole due to the unavoidable variation of an abrasive jet. Accuracy is not good due to stray cutting. A dust collection system is a basic requirement to prevent atmospheric pollution and health hazards so the extra cost will be there. Nozzle life is limited (300 hours). Abrasive powders cannot be reused as the sharp edges are worn and smaller particles can jam the nozzle. A small standoff distance can damage the nozzle. The process accuracy is poor because of the flaring effect of the abrasive jet. Deep holes will have a taper. AJM Process is not environment-friendly and causes pollution. Airborne abrasives can cause a hazardous atmosphere. APPLICATION: It is used for abrading and frosting glass, ceramics, and refractories and it is more economical as compared to etching or grinding. Cleaning of layering of metals like resistive coating. Deflating small castings and trimming of parting lines of injection moulded parts and forgings. It is used for engraving registration numbers on toughened glass for car windows. AJM is used for cutting thin fragile components like germanium, silicon, quartz, mica, etc. Abrasive jet machining is used effectively for micro module fabrication. Deburring etching, drilling, Cutting, and polishing of hard and brittle materials. It can be used for micromachining of brittle materials. It is used in fine drilling and aperture drilling for an electronic microscope. Used for cleaning metallic moulds and cavities. Cleaning surfaces from corrosion, paints, glues, and other contaminants. Deburring of surgical needles and hydraulic valves, nylon, Teflon, and Delran. Engraving on glass using rubber or metallic masks. CONCLUSION: AJM process is receiving more and more attention in the machining areas, particularly for the processing of difficult-to-cut materials. Its unique advantages over other conventional and unconventional methods make it a new choice in the machining industry. Various materials can be machined using this process. Efficiency of Abrasive Jet Machining process is impacted by nozzle wear, which intern depends on certain process as well as geometrical parameters such as nozzle length, nozzle diameter, orifice size, nozzle inlet angle. This process is smooth and free from vibration. This process having very low capital investment as well as heat generated in this process becomes very less, so this process is used in various industrial application. REFERENCES:1) https://learnmechanical.com/abrasive-jet-machining/ 2) http://www.minaprem.com/micro-machining/ajm/advantages-and-limitations-ofabrasive-jet-machining-ajm-process/ 3) https://learnmechanical.com/abrasive-jet-machining/ 4) https://crbtech.in/abrasive-jet-machining-principles-advantages-limitations
