The metal removal rate, end wear, and surface finish results are given for each cut. - Generally the rate of metal removal for various machining processes are as follows: 1. This energy is controlled by the peak amperage and the length of the on-time. The machining parameters studied in this research are current (4.5A, 5.5A, and 6.5A) and concentration of the powder (30g/l, 60g/l, and 90g/l). B. EDM 2. This study focused on the machining of SKD61, SKD11, and SKT4 … Expected results — Lower metal removal rate and improved surface finish. In ultrasonic machining process, the material removal rate will be higher for materials with (a) higher toughness ... 4. A circular hole of 25 mm diameter and depth of 20 mm is machined by EDM process. Electrochemical Machining (ECM) Ultrasonic Machining (USM) Electron Beam Machining (EBM) Laser Beam Machining (LBM) and. This is what happens — The amount of energy per discharge and the amount of workpiece material removed per discharge remain unchanged. $ 4\times10^4\;IT^{-1.23} $ , where $ I=300 $ A and the melting point of the material, $ T=1600^\circ C $ . then remains steady. takes place by bombardment of fine grained particle. The off-time was cut in half to produce a 67% duty cycle and the metal removal increased. Increasing current density and decreasing frequency of sparks. The following examples (figures 3-12 and 3-13) show different parameters, but both have the same average current value. These two parameters directly affect the size of the overcut and the roughness of the finish. The material removal rate (in mm 3 /min) is expressed as. The improvement in electrode wear, expressed as End Wear (EW), at the higher duty cycle should also be noted. Voltage — Before current can flow, the open gap voltage increases until it has created an ionization path through the dielectric (figure 3-2). Effects of duty cycle changes on metal removal rate and surface finish. Once the current starts to flow the voltage drops until it stabilizes at the working gap level. The on-time is 40 microseconds and the off-time is 60 microseconds. 20. Four cuts were made using the parameters of the four examples to compare results. Figure 3-8. The important machining parameters were selected as peak current, flushing pressure and pulse-on time. The effect of pulse off time on MRR changes with peak ampere. The optimization was performed in two steps using one factor at a time for preliminary evaluation and a Box-Behnken design involving three var… However, utilizing high-frequency vibration, especially in ultrasonic range consumes a lot of setup cost. Electric Discharge Machining (EDM) has metal removal rate of about 10-20 mm 3 /s. concentration of abrasive in slurry (in USM process), d) initially decrease and The Guide to Electrode Polarity Chart in Chapter 8 shows some workmetal exceptions (page 8-2). become more stable thus increasing the material removal rate and improve the surface quality as compared to conventional EDM. 48 EDM – Material Removal Rate In EDM, the metal is removed from both workpiece and tool electrode. stable and then decreases, 2.The size of abrasive When the melting point and latent heat of melting increases in EDM, the. Electrical Discharge Machining (EDM) is a non traditional machining and electro thermal process in which material from the workpiece is removed by using electrical discharges (sparks). Electrical discharge machining is a machining method www.gtu-mcq.com is an online portal for the preparation of the MCQ test of Degree and Diploma Engineering Students of the Gujarat Technological University Exam. There is no direct contact between the workmetal and the electrode. All of the examples used positive polarity, tool steel as the workpiece, POCO EDM-3 as the electrode material, and a 5-minute cutting time. What happens to the surface roughness values if the MRR increases in EDM? (Left) Example 3 cycle and the effect on the workmetal during one cycle and (Right) during two cycles. material removal rate. Yusuf Keskin et Electrical Discharge Machining (EDM) is right choice of machining this material. Electrical discharge machining, generally known as EDM, is a thermoelectric process of non-conventional machining, where electrical discharges occur between two electrodes immersed in a dielectric fluid promoting heating, vaporization and removal of material. Frequency changes the surface finish of the workmetal. Match the following metal forming processes with their associated stresses in the work piece. The electrode is always smaller than the width of the final cavity to allow for the spark gap. For a given peak current and a fixed on-time, spark energy will remain constant even though the average current may be varied considerably by changing the off-time. The duty cycle remains at 40% and the frequency increases to 20 kHz. material is not generally machined by USM, 11.Increasing volume a) Increases b) Decreases c) Decrease and increase d) … Current increases until it reaches peak current during the effective on-time portion of the cycle. Arrange the processes in the increasing order of their maximum material removal rate. Polarity refers to an electrical condition determining the direction of the current flow relative to the electrode. C. ECM 3. a) Decreases b) Increases c) Increase and then decrease d) All of the mentioned 10. Often the desired result can be achieved by more than one means. (SiCw/Al) composites [3]. 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, … When the optimum on-time for each electrode material/workmetal combination is exceeded, the Metal Removal Rate (MRR) actually starts to decrease. Decreasing both current density and frequency of sparks. The energy used in any given time period remains the same. Each spark, regardless of off-time variation, will remove the same volume of workpiece material, resulting in the same surface finish value. MRR in 15 vol. Machine settings are 40 µs on, 60 µs off, and 50 amps peak current. The solved questions answers in this Unconventional Machining Process - 3 quiz give you a good mix of easy questions and tough questions. ... (b) 2 1 4 3 (c) 4 1 2 3 (d) 4 3 2 1. from an experiment done by Kumar et al. When the mass flow rate of the abrasive increases the material removal rate also increases. In this study, experiments were performed by varying the peak current and keeping other parameters constant in order to investigate the effect of peak current on material removal rate (MRR) in EDM of Al2O3. This will cause the next spark to be unstable. Example 4 — This cut shows a peak current change. Advanced Machining Process - Mechanical Engineering (MCQ) questions and answers Home >> Category >> Mechanical Engineering (MCQ) questions and answers >> Advanced Machining Process 1) The Laser Beam Machining process can be carried out, when the media for … EDM, and a high material removal rate and low relative ... increases, the eroded materials are easily washed away, and the EDM process becomes stable; therefore, the wear ratio decreases. In the previous example, varying the frequency improved the finish, but in this example the results are quite different. a) Electrode tool b) Work piece c) Electrode tool & … The tungsten copper composite material is employed as tool material. Figure 6-2. Since two cycles can be completed in the same amount of time (100 µs), the metal removal rate should not change. These large craters will create a rougher surface finish. applications wherein increased importance is placed on the graphite electrode material utilized. (MRR). This test is comprising of 20 questions on Manufacturing Processes.Ideal for the candidates preparing for semester exams, IES, GATE, PSUs, UPSC and other entrance exams.1 mark for each correct answer and 0.25 mark will be deducted for wrong answer. However, the surface layer properties after EDM require additional finishing operations in many cases. The higher the frequency, the finer the surface finish that can be obtained. The complete cycle time is 100 microseconds. Material Removal Rate, Electrode Wear Rate, and Surface Roughness Evaluation in Die Sinking EDM with Hollow Tool through Response Surface Methodology TeepuSultan,AnishKumar,andRahulDevGupta Department of Mechanical Engineering, M. M. University, Mullana, Ambala, Haryana, India Correspondence should be addressed to Anish Kumar; anish kaushik@redimail.com Received May; … The effectiveness of EDM process with tungsten copper electrode is evaluated in terms of the material removal rate. a)increases continuously. In theory, the shorter the off-time the faster the machining operation will be; however, if the off-time is too short, the ejected work piece material will not be swept away by the flow of dielectric and the fluid will not be deionized. Generally, the higher duty cycles mean increased cutting efficiency. Figure 6-2 compares the metal removal rate of the five EDM classifications of graphite under one set of conditions. Example 2 — This cut shows a frequency change. Experiments were conducted by selecting different operating levels for the three parameters according to Taguchi’s Design of Experiments. b. USM, LBM, EBM, EDM, ECM. The width of the EDM cavity is always larger than the electrode and the difference is called the overcut or overburn (figure 3-5). These example cuts (figure 3-10) and the resulting data show the relationship between surface finish, metal removal rate and electrode wear (figure 3-11) that is controlled by the amperage and length of on-time and frequency. The machining parameters studied in this research are current (4.5A, 5.5A, and 6.5A) and concentration of the powder (30g/l, 60g/l, and 90g/l). Figure 3-3. The electrode wear has increased due to the reduction of on-time. Using the original parameters of 40 µs on-time and 60 µs off-time, the duty cycle remains 40% and the frequency remains at 10 kHz. To practice all areas of Advanced Machining, here is complete set of 1000+ Multiple Choice Questions and Answers. METHODS OF IMPROVING MRR Dry EDM The MRR increased when the discharge power density on the working surface exceeded a certain threshold limit due to thermally activated chemical reaction between the gas and workpiece material. Modeling of Material Removal on Machining of Ti-6Al-4V through EDM using Copper Tungsten Electrode and Positive Polarity . METHODS OF IMPROVING MRR Dry EDM The MRR increased when the discharge power density on the working surface exceeded a certain threshold limit due to thermally activated chemical reaction between the gas and workpiece material. There is an optimum mixing ratio (mass fraction of the abrasive in the jet) for which the metal removal rate is the highest. Average current is the average of the amperage in the spark gap measured over a complete cycle. The above example shows how to determine the average machining current. 7. While there are many methods used to determine the right material for a job, we believe there are five factors that mean the difference between success and failure, profit and loss. In this example (figure 3-7), the duty cycle remains constant, but the on-time and off-time have been cut in half. Major variations in surface finish occur only when on-time or peak current change. The mass flow rate of the abrasive particles depends on the pressure and the flow rate of the gas. In real conditions, discharge current and discharge duration increase material removal rate, as well as the increase of gas bubbles in the discharge zone. b) decreases continuously. MCQ Question. 005 mm to 0.50 mm. In abrasive jet machining, as the distance between the nozzle tip and the work surface increases, the material removal rate (A) Increases continuously (B) Decreases continuously (C) Decreases becomes stable and then increases ... I.C Engines Multiple Choice Questions with Answers - Set 02. a) Increases b) Decreases c) Decrease and increase d) … There is an optimum mixing ratio (mass fraction of the abrasive in the jet) for which the metal removal rate is the highest. The peak current remains at 50 amps. Metal is removed on which of the components in electro discharge machining? 9. Example 3 — This cut shows a duty cycle change. place in AJM due to, 16.As the stand off The longer the on-time pulse is sustained the more workpiece material will be melted away. Analysis is carried using the response surface method and Anova analysis. According to a results, the material removal rate of dry EDM is about 6 times larger than that of oil EDM. However, speed is not usually the only consideration when cutting cavities. Arrange the processes in the increasing order of their maximum material removal rate. 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