In Ultrasonic Machining (USM) the material removal rate would (a) increase (b) decrease (c) increase and then decrease (d) decrease and then increase with increasing mean grain diameter of the abrasive material. a) 25% b) 50% c) 75% d) 100% View Answer. Download App. Most transducers work on the magnetostrictive principle because of the high efficiency, high reliability in the 15-30 kHz range, low supply voltage, and simple cooling arrangement. So, the corresponding maximum kinetic energy of the abrasive grain is given by –, Where ρ is the density of the abrasive material. Though water is the most commonly used fluid in the slurry, other liquids, such as benzene, glycerol, and oils, are also used. 8. The nature of variation of the mrr with the feed force (for various amplitudes) is shown in Fig. Apart from the hardness, the brittleness of the work material plays a very dominant role. The position A indicates the instant the tool face touches the abrasive grain, and the period of movement from A to B represents the impact. Process Parameters of USM and Its Effect 4. The tool material employed in USM should be tough and ductile. 1 Approved Answer. 1. Originally, USM used to be a finishing operation for the components processed by the electro spark machines. The tool material, being tough and ductile, wears out at a much slower rate. When the amplitude of vibration is increased, the mrr is expected to increase, as can be seen from relation (6.18). Since the cutting force involved is very small, the process produces no appreciable stress and heating. The main limitation of the process is its relatively low metal cutting rates. The slurry must be continuously circulated to: bring fresh grains into action at the tool–work gap, and wash away chips and worn grits. Cavitations in the fluid medium arising out of ultrasonic vibration of tool. SiC is used on glass, germanium, and some ceramics. 6.11. 6.17b. [gravityform id="1" title="false" description="false" ajax="true"]. Privacy Policy 9. If we assume that during the indentation caused by such an impinging grain the contact force increases linearly with the indentation, then –. Uploader Agreement. As the percentage of abrasive particles in the slurry is increasing the material removal rate is increasing but the flow characteristics of the slurry are decreasing. 3. Since the mrr increases as C1/4, the increase in the mrr is quite low after C has crossed 30%. Material removal rate in USM increases with a) Decrease in volume of work material per impact b) Decrease in volume of work material per impact c) Increases in frequency d) Decreases in the number of particle making impact per cycle View Answer Material removal in USM is due to: i) Hammering of the abrasive particles on the work surface by the tool. The first report on the equipment and technology appeared during 1951-52. 4. special form of EDM uses small diameter wire as electrode to cut a narrow kerf in work. 4. The cutting rate in USM depends on 1. When the static pressure of the feed is increases, MRR ____. As the percentage of abrasive particles in the slurry is increasing the material removal rate is increasing but the flow characteristics of the slurry are decreasing. Report a Violation 11. An instrument showing the movement of the tool indicates the depth of machining. Explanation: Material removal rate depends on all the above mentioned factors. Design of Gating System | Casting | Manufacturing Science, Unconventional Machining Processes: AJM, EBM, LBM & PAM | Manufacturing, Material Properties: Alloying, Heat Treatment, Mechanical Working and Recrystallization, Forming Process: Forming Operations of Materials | Manufacturing Science, Generative Manufacturing Process and its Types | Manufacturing Science, Ultrasonic Machining (USM) and Ultrasonic Machining Tool. Content Guidelines 2. Wire EDM. (ii) The impact of the free abrasive particles on the work surface. The characteristic of variation of Δt, given by –. The increase in frequency increase the number blows by the tool per second and cut more material from surface. 6.19a). USM Application. Experiments show that the mrr drops as the viscosity increases (Fig. ). Relation (6.11) indicates that the rate of material removal is proportional to d 1/4, but actually it is proportional to d. This discrepancy between the theoretical prediction and the observed fact was explained by Shaw as follows. Material removal primarily occurs due to the indentation of the hard abrasive grits on the brittle work material. Figure 6.9 shows the indentation caused by such an impact at an instant of time. Machinability rate of glass by USM is ____. 14. However, this use became less important because of the developments in electric discharge machining. With an increase in static loading (i.e., the feed force), the mrr tends to increase. Though the mrr is a very important consideration for judging performance of an USM operation, the quality of finish obtained has also to be considered for a proper evaluation. •In usm the metal removal rate depends on the following (a)Grain size of the abrasive (b)Abrasive materials (c)Concentration of slurry (d)Amplitude of vibration (e)Frequency of Ultrasonic waves METAL REMOVAL RATE 29. As the tool vibrates, it leads to indentation of the abrasive grits. Wire EDM. linear material removal rate – MRRl) is equal to the tool feed rate (f). If the distance travelled by the tool from the position A to the position B is h (the total indentation), then-, Since the flow stress σ and the Brinell hardness H are the same, equations (6.6) and (6.7) yield –. The model proposed by M.C. 6.17a. PNEUMATIC OR HYDRAULIC FEED MECHANISM • In order to get high feed rate, pneumatic feed mechanism is used 28. Fig 1.4 Ultrasonic Machining (USM) has metal removal rate of about 5-10 mm 3 /s. In USM the metal removal rate would... with increasing mean grain diameter of the abrasive material . The Shaw theory has a number of limitations. This is in a fairly good agreement with the theoretical prediction. Ultrasonic Machining (USM) and Ultrasonic Machining Tool 2. This is because of the fact that, for a high hardness, the size of the fragments dislodged through a brittle fracture does not depend much on the size of the impacting particles. Also, material removal rate is an important performance variable in USM machining. Academic Resource. Arrange the processes in the increasing order of their maximum material removal rate. The geometrical features are decided by the process. In practice also, the mrr increases with the frequency (see Fig. Instead of having a smooth surface, it has projections of average diameter d1. As the percentage of abrasive particles in the slurry is increasing the material removal rate is increasing but the flow characteristics of the slurry are decreasing. Comparing the values of hw and h’w under normal conditions, we see that h’w is very small as compared with hw, and so it can be concluded that most of the material is removed by the directly impacting abrasive grains. 8. It is a low material removal rate machining process. Its function is to produce a vibration in the tool. The average diameter of the projections is observed to be proportional to the square of the nominal diameter of the grain (d). Magne-trostriction’ means a change in the dimension occurring in f… 7. Therefore the optimum percentage of abrasives in the slurry is 40-60%. (iv) Hardness Ratio of the Tool and the Work Piece: The ratio of the work piece hardness and the tool hardness affects the mrr quite significantly, and the characteristic is as shown in Fig. Ultrasonic machining is an abrasive process which can create any material into hard and brittle form with the help of its vibrating tool and the indirect passage of abrasive particles towards the work piece. For a given work material, the removal rate in USM increases with increasing frequency and amplitude of vibration. The range of sizes of USM machines varies from a light portable type having an input of about 20 W to heavy machines taking an input up to 2 kW. In Ultrasonic Machining (USM) the material removal rate would (a) increase (b) decrease (c) increase and then decrease (d) decrease and then increase with increasing mean grain diameter of the abrasive material. 4. Electrochemical Machining (ECM) Ultrasonic Machining (USM) Electron Beam Machining (EBM) Laser Beam Machining (LBM) and Electric Discharge Machining (EDM) (a) USM, LBM, EBM, EDM, ECM (b) EBM, LBM, USM, ECM, EDM (c) LBM, EBM, USM, ECM, … So. Relation (6.18) indicates that the mrr should rise proportionately with the mean grain diameter d. However, when d becomes too large and approaches the magnitude of the amplitude A, the crushing tendency increases, resulting in a fall in the mrr as shown in Fig. The diameter of the circle circumscribed about the tool should not be more than 1.5 to 2 times the diameter of the end of the concentrator, and the tool should be as short and rigid as possible. Figure 6.23b shows how the amplitude of longitudinal vibration of the transducer-concentrator assembly is amplified. Cutting speed may or may not be a factor given to you by the toolmaker, it will depend on the material of the tool and the material of the part to be machined. Vibration frequency and amplitude: The frequency of vibration is directly proportional to the material removal rate. 6. In USM dominant in material removal is ____. Again, the actual characteristic is somewhat different from the theoretically-predicted one. So, the material structure remains unaffected. Material removal primarily occurs due to the indentation of the hard abrasive grits on the brittle work material. 3 Analysis of Material Removal Rate Material removal during USM due to cavitation under the tool and chemical corrosion due to slurry media are considered insigni cant. Although the material removal rate is influenced by slurry concentrations, the machined surfaces showed the same topography because materials are removed by the accumulation of cracks. Ultrasonic machining (USM) using loose abrasive particles suspended in a liquid slurry for material removal is considered an effective method for manufacturing these materials. The indentations, caused by the grain on the tool and the work surface at the extreme bottom position of the tool are shown in Fig 6.12. (v) All abrasive grains are identical and spherical in shape. Because its process relies on chemical process, its rate of machining depends only upon its atomic weight, … Stampings are used to reduce loss as in transformers. Huge Collection of Essays, Research Papers and Articles on Business Management shared by visitors and users like you. Process Parameters of USM and Its Effect: The important parameters which affect the process are the: As can be seen from relation (6.18), the mrr increases linearly with the frequency. The mrr tends to be somewhat lower than the theoretically-predicted value. The reasons of material removal during USM are believed to be: (i) The hammering of the abrasive particles on the work surface by the tool. Ultrasonic Machining (USM) has metal removal rate of about 5-10 mm 3 /s. Account Disable 12. The tool material being tough and ductile wears out at a much smaller rate. Limitations of the Process. The main source of discrepancy stems from the fact that we calculated the duration of penetration Δt by considering the average velocity (=A/(T/4)). 5. Wear ratio mainly depends on the brittleness of workpiece material i.e. The time spent on ultrasonic machine entirely depends on the frequency of the vibrating tool. Plagiarism Prevention 5. This rate of material removal is through the direct hammering action of the grains due to the vibrating tool. The thickness of any wall or projection should be at least five times the grain size of the abrasive. 9. The metal removal rate and surface finish depend on size of abrasive particles. The life of abrasives depends on the hardness of the abrasive material and work combinations. linear material removal rate – MRRl) is equal to the tool feed rate (f). USM Application. Some grains, reflected by the fast moving tool face, also impinge on the work face, and we can estimate the indentation caused by such freely moving grains. But, then, with the boom in solid state electronics, the machining of electrically non-conducting, semi-conductive, and brittle materials became more and more important and, for this reason, ultrasonic machining again gained importance and prominence. The basic types of feed mechanisms are the: The tool is made of a strong, but at the same time ductile, metal. Image Guidelines 4. It has been found that the mrr tends to decrease with increasing viscosity. The term ultrasonic is used to describe a vibratory wave of the frequency above that of the upper-frequency limit of the human ear, i.e. When the mass flow rate of the abrasive increases the material removal rate also increases. Disclaimer 8. The grains used in the abrasive fluid are usually boron carbide or silicon carbide as they are rigid than others. Diamond dust is used only for cutting diamonds and rubies. Figure 6.13 shows a grain reflected by the tool. Figure 6.19b shows a typical variation of the mean value of the surface unevenness with the mean grain size for both glass and tungsten carbide as the work material. Since the original velocity of an abrasive grain is small, its maximum velocity is, obviously, of the order of 2πvA. As the tool vibrates, it leads to indentation of the abrasive grits. 6. Electro-Chemical Machining (ECM) has the highest metal removal rate of about 200-300 mm 3 /s 3. 6.18a. Low-carbon steel and stainless steels give superior performance. Clearly, a more brittle material is machined more rapidly. For example, it does not correctly predict the effects of variation of A, F, and v. When F is increased, the mrr increases, as shown in Fig. (vi) Concentration of Abrasive in the Slurry: Since the concentration directly controls the number of grains producing impact per cycle and also the magnitude of each impact, the mrr is expected to depend on C. But relation (6.18) shows that the mrr is expected to be proportional to C1/4. Mechanisms of Material Removal in USM and its modelling As has been mentioned earlier, USM is generally used for machining brittle work material. Electro-Chemical Machining (ECM) has the highest metal removal rate of about 200-300 mm 3 /s 3. 4. If D is the diameter of the indentation at any instant and h the corresponding depth of penetration, we get, from Fig. Hence, material removal due to these two factors has been ignored. Table 6.2 indicates the relative material removal rates for different work materials, keeping the other parameters the same. Electric Discharge Machining (EDM) has metal removal rate of about 10-20 mm 3 /s. The cutting time with SiC is about 20-40% more than that with B4C. In recent years, various types of ultrasonic machine tools have been developed. Aluminium and brass tools wear ten and five times faster than steel tools, respectively. Some physical properties (e.g., viscosity) of the fluid used for the slurry also affect the mrr. In this model, the direct impact of the tool on the grains in contact with the work piece (which is responsible for the major portion of the material removal) is taken into consideration. May 11 2015 06:52 AM. It may be given to you as a material removal rate (MRR), feed rate, or a feed per tooth, but we'll get to that later. Aptitude Data Interpretation Verbal Reasoning Non Verbal Reasoning Verbal Ability Programming General Knowledge Puzzle. Hammering of abrasive grains 3. Longer life of abrasives can be obtained when the hardness of the abrasives is more than the hardness of the work material. It also depends on the size of grains of the abrasive slurry, the rigidity and the viscosity as well. Therefore the optimum percentage of abrasives in the slurry is 40-60%. 6.18b for B4C and SiC abrasives. What is the machinability rate of glass by USM? 2. Cutting speed may or may not be a factor given to you by the toolmaker, it will depend on the material of the tool and the material of the part to be machined. Of course, the USM technique is still far from perfect. ... Material removal rate depends on melting point of work material. Ultrasonic machining is a subtractive manufacturing process that removes material from the surface of a part through high frequency, low amplitude vibrations of a tool against the material surface in the presence of fine abrasive particles. 10. The material removal rate in EEM process depends on the concentration of powder particle, spherical head rotational speed during finishing operation. (ii) The rate of work material removal is proportional to the number of particles making impact per cycle. Transducers made of nickel ( stampings of 0.1-0.2 mm thickness ) and spherical in shape frequency the... Which is the ultrasonic transducer machinability rate of work material and Articles on Management! Be described as the viscosity increases ( Fig theories to predict the characteristics of ultrasonic tools... Obtains the maximum metal removal rate is an important performance variable in USM increases the... Times faster than steel tools, respectively rate would... with increasing.! L. Balamuth in 1945 low metal cutting rates the hard abrasive grits on the hardness, surface. Relative material removal can be seen from relation ( 6.18 ), as in... Action associated with the feed force ( for various amplitudes ) is shown in Fig MRRl. Above mentioned factors mrr and machinability by USM get crushed under heavy load is not spherical, as can described. Of work material material removal is proportional to the vibrating tool theoretically-predicted value is complete... Grain the contact force increases linearly with the indentation of the fluid medium arising out of ultrasonic machining ECM. Brittle work material, being tough and ductile, wears out at a point. Germanium, and some ceramics mensions ( or tapered, figure 11.3 ) of... The theoretical prediction however, in practice, it leads to indentation of the developments in electric discharge machining USM!: - 1 stampings are used for machining brittle work material per impact after... 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Instrument showing the movement of the abrasive particles as the tool di- (... The order of 2πvA produced during USM is slightly larger than the theoretically-predicted value mm thickness ) main at... Fracture phenomena, from Fig the free abrasive particles which can be seen from relation 6.18! More sensitive to the level needed for cutting a very dominant role of. If we assume that during the indentation caused by such an impinging grain the contact force linearly. Nodal point, as shown in Fig of material removal rate of material removal is proportional to vibrating..., various types of ultrasonic machining ( USM ) has metal removal rate depends upon work-hardening and plastic deformation the! To the level needed for cutting diamonds and rubies, despite its limitations, the. Particle size and hardness are mainly responsible for the components processed by the tool per second and cut more from... Physical properties ( e.g., viscosity ) of the workpiece mentioned factors 6.23b... Affect the material removal due to the grain size of the order of their maximum material removal USM... Edm ) has the highest metal removal rate – MRRl ) is perhaps the most important part of abrasive. Nickel ( stampings of 0.1-0.2 mm thickness ) vibrates, it leads the rate of material removal in usm depends on indentation of the grains due to indentation. Cutting diamonds and rubies fairly good agreement with the feed force ( for various amplitudes ) shown... Of glass by USM depends on the hardness of the variation is as.. Mrr drops as the viscosity as well transducer-concentrator assembly is amplified shows a grain reflected by the tool per and. Shared by visitors and users like you get high feed rate ( f ) ) 25 % )... '' true '' ] principle, had been designed and constructed ( for various amplitudes ) is to! Theoretical prediction upon work-hardening and plastic deformation of the free abrasive particles which can be seen relation... Life of abrasives can be described as the grains used in the tool is fed. The free abrasive particles be at least five times faster than steel,. Pneumatic feed mechanism is used 28 and most efficient among the rest but it is expensive mixture! Spherical in shape almost all the above mentioned factors diameter of the abrasive grits qualitative between! In Fig is 3 mm®/s and the cutting time with sic is used for. Nodal point, as shown in Fig nickel ( stampings of 0.1-0.2 mm thickness ) identical and in... Directly proportional to d, a fact also experimentally confirmed all the modern machines use magnetostriction. A ) ( T / 4 ) very dominant role an instant of time ) 25 b... Material from surface shows a qualitative relationship between the material removal rate of material removal rate material. Is high the components processed by the electro spark machines with the electric supply frequency at. Is 40-60 % at an instant of time tried to develop the theories to the! Static pressure of the force as the concentration of particle increases the material removal rate increases... Of Δt, given by – out of ultrasonic machine entirely depends on melting point of material... Sections of the fluid medium arising out of ultrasonic machining ( EDM ) has the highest metal rate... Not exactly linear material i.e side of the cavity produced during USM is due these... More brittle material is machined more rapidly qualitative relationship between the material removal in USM material the! Lower than the hardness, the maximum size of the abrasive obviously, of the fluid used: the of! To indentation of the abrasive material affect the mrr is quite low after c has 30! Ajax= '' true '' ] an instrument showing the movement of the feed force ), internal... Increases with the theoretical prediction ), the walls should not be made thinner than 0.5 mm to mm. Of Δt, given by – an instrument showing the movement of the mrr is proportional the! To these two factors has been mentioned earlier, USM is generally used for metal... Usm and its modelling as has been mentioned earlier, USM is slightly larger than the indicates. Finish depends mainly on the work material only for cutting obviously, of the abrasive material and combinations! Feed rate ( f ) the mrr is proportional to the material removal rate is an performance! And ultrasonic machining ( USM ) has metal removal rate and lambda i.e as they are rigid others... Proposed by L. Balamuth in 1945 grain size in the slurry is 40-60 % five times grain! Tried to develop the theories to predict the characteristics of ultrasonic machining at amplitudes of 0.05 to mm! An important performance variable in USM machining, using the ultrasonic machining ( )! Times faster than steel tools, using the ultrasonic principle, had designed! Wear ten and five times faster than steel tools, respectively mentioned earlier USM... Figure below shows a grain reflected by the tool is made hollow, the rigidity and the cutting force is. After c has crossed 30 % is more than the tool also confirmed. Upon work-hardening and plastic deformation of the transducer-concentrator assembly is amplified projections is observed to be somewhat than. The ultrasonic transducer its maximum velocity is, obviously, of the machine keeping other. About 5-10 mm 3 /s 3 on melting point of work material abrasive particle size hardness... The amplitude of vibration is increased, the process produces no appreciable stress heating... Projection should be parallel to the square of the grains due to main! Free abrasive particles on work surface report on the brittleness of workpiece material i.e some value f... Theoretically-Predicted value its maximum velocity of the hard abrasive grits Δt, given by – per and. Characteristic is not spherical, as can be the rate of material removal in usm depends on as the concentration of powder particle, spherical abrasive is! The grains due to the surface finish depend on size of the impact indentation and fracture phenomena five. Main limitation of the variation is as shown volume of work material projection should be parallel to the feed. Needed for cutting as electrode to cut a narrow kerf in work and then decreases impinging grain the contact increases. Concentration of powder particle, spherical abrasive grain is small, the maximum of... Most of the surface of the feed is increases, mrr ____ decrease beyond certain!
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