is used for converting electrical energy into mechanical energy in USM, 19.The following device is Answer: c Explanation: MRR is inversely proportional to a melting point of work piece. Electrical discharge machining (EDM) is a relatively modern machining process having distinct advantages over other machining processes and can machine Ti alloys eﬀectively. Average current is the average of the amperage in the spark gap measured over a complete cycle. Match the following metal forming processes with their associated stresses in the work piece. The result is an improved surface finish with little change in the metal removal rate. This paper reviews the research trends in EDM process by using water and powder mixed dielectric as dielectric fluid. The tungsten copper composite material is employed as tool material. The primary objective in EDM of materials is always having higher material removal rate (MRR) in order to improve the productivity. However, the surface layer properties after EDM require additional finishing operations in many cases. Since all the work is done during on-time, the duration of these pulses and the number of cycles per second (frequency) are important. Abrasive slurry. The big change is that the shortened off-time allows twice as many discharges to occur over the same length of time. 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. In the present work, an attempt has been made to model material removal rate, electrode wear rate, and surface roughness through response surface methodology in a die sinking EDM process. The result is an improved surface finish with little change in the metal removal rate. Machine settings are 40 µs on, 10 µs off, and 50 amps peak current. 20. Electric Discharge Machining (EDM) Choices. The following examples (figures 3-12 and 3-13) show different parameters, but both have the same average current value. Electrode — A long on-time can put the electrode into a no-wear situation. a) Decreases b) Increases c) Increase and then decrease d) All of the mentioned 10. 9. Short on-times remove very little metal and create smaller craters. The mass flow rate of the abrasive particles depends on the pressure and the flow rate of the gas. in the following type of machining process. Frequency changes the surface finish of the workmetal. The material removal rate depends on type of abrasive powders. Arrange the processes in the increasing order of their maximum material removal rate. 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. The duty cycle remains at 40% and the frequency decreases to 10 kHz. This research work describes the effect of powder concentration in dielectric fluid during electrical discharge machining (EDM) of mild steel on material removal rate (MRR), electrode wear rate (EWR) and work surface roughness (Ra). The off-time was cut in half to produce a 67% duty cycle and the metal removal increased. MRR = 1.2 in3/hr EW = 1.4 % SF = 430 µin Ra. work surface is called which one of the following, 13.In abrasive water jet The results are an improved surface finish, a much lower metal removal rate and an increase in the electrode wear. What happens to the material removal rate if the sparks are very less in EDM? Get PDF (1 MB) Abstract. Machining parameters for Example 4 and the effect on the workmetal during one cycle. As an example, if your RDOC is.500″, your ADOC is.100″ and your Feed Rate is 41.5 inches per minute, you’d calculate MRR the following way: MRR =.500″ x.100″ x 41.5 in/min = 2.08 cubic inches per minute. Material removal rate in EDM increases with a) Increase in melting point of work piece b) Decrease in Current c) Decrease in melting point of work piece d) None of the mentioned View Answer. machining, as the distance between the nozzle tip and the work surface Material removal rate (MRR), Electrode wear rate (EWR) and Surface roughness (R a). This set of Advanced Machining Processes Multiple Choice Questions & Answers (MCQs) focuses on “EDM-Material Removal Rate”. Four cuts were made using the parameters of the four examples to compare results. The effectiveness of EDM process with tungsten copper electrode is evaluated in terms of the material removal rate. Figure 3-12. The surface finish at all three duty cycles changed very little because the crater created by the spark did not change. Low frequencies are generally used for roughing operations. What happens to the material removal rate if the sparks are very less in EDM? Machine settings are 40 µs on, 60 µs off, and 50 amps peak current. slurry are driven at a high velocity against the work by a tool vibrating at This will cause the next spark to be unstable. The material removal increases with the increase in machining time, but the machining rate is different for different workpiece materials. 1. d.Increase in the melting temperature of the workpiece material, T m. … Metal removal is directly proportional to the amount of energy applied during the on-time. 21.In WJM, removal of metal The constant value throughout these examples has been the peak current. MCQ on Mechanical Energy Based Unconventional Machining Process 1.In abrasive jet machining, as the distance between the nozzle tip and the work surface increases, the material removal rate a)increases continuously Due to impaired evacuation of machining products, a portion of the discharge energy is spent on re-melting and evaporation of solidified metal particles. 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. When the mass flow rate of the abrasive increases the material removal rate also increases. a) Increases b) Decreases c) Decrease and increase d) … The material removal rate (in mm 3 /min) is expressed as. Expected results — Lower metal removal rate and improved surface finish. Correct Answer. High voltage settings increase the gap, which improves the flushing conditions and helps to stabilize the cut. (Left) Example 3 cycle and the effect on the workmetal during one cycle and (Right) during two cycles. Join our social networks below and stay updated with latest contests, videos, internships and jobs! Variations in metal removal rate (in3/hr) occur because of differences in spark frequencies due to changes in nonproductive time (off-time). Participate in the Sanfoundry Certification contest to get free Certificate of Merit. Electrical discharge machining (EDM) is an advanced technology used to manufacture difficult-to-cut conductive materials. The energy used in any given time period remains the same. a) Electrode tool b) Work piece c) Electrode tool & … The duty cycle increases to 80% and the frequency remains at 20 kHz. 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, … Example 3 — This cut shows a duty cycle change. Extended on-times also allow more heat to sink into the workpiece and spread, which means the recast layer will be larger and the heat affected zone will be deeper. grains in abrasive jet machining ranges from, 3.The vibrating frequency 2. Increasing current density and decreasing frequency of sparks. 2.The size of abrasive grains in … Voltage — Before current can flow, the open gap voltage increases until it has created an ionization path through the dielectric (figure 3-2). 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. Both examples have approximately the same metal removal rate, but the example in figure 3-13 would produce a finer finish. • Material Removal Rate: – Roughing - removes large amounts of material, at high feeds and depths, low speeds – Finishing - Achieves final dimensions, tolerances, and finish, Low feeds and depths, high cutting ... As φ(from 10° to 35°) increase, γ(from 5 to 2) decreases. The duty cycle is calculated by dividing the on-time by the total cycle time (on-time + off-time). The on-time is 40 microseconds and the off-time is 60 microseconds. ASWDC (App, Software & Website Development Center) Darshan Institute of Engineering & Technology (DIET) takes place by bombardment of fine grained particle. This work presents an attempt to use a low-frequency vibration on workpiece of stainless steel (SS 304) during EDM process. 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 effectiveness of EDM process with tungsten copper electrode is evaluated in terms of the material removal rate. Expected results — Improved surface finish with no significant change in metal removal rate. Generally with graphite, a positive electrode gives better wear and a negative electrode gives better speed. Now, the material removal rate ( in mm 3 /min ) is done during on-time use is percentage... 10 microseconds and off-time have been cut in half observed in 1770 by Joseph Priestley off-time is 30 microseconds off-times. Increase in the increasing order of their maximum material removal rate less in EDM often desired! It stabilizes at the working gap voltage off, and average current value three duty mean! Primary objective in EDM the EDM process the work surface increases, the surface roughness R! 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