This set of Manufacturing Processes Multiple Choice Questions & Answers (MCQs) focuses on “Wire-cut EDM – 5”.
1. Which of the following materials is not machined by wire cut EDM?
c) Tool steel
Explanation: It can machine anything that is electrically conductive, from relatively common materials such as tool steel, aluminium, copper, and graphite, to exotic space-age alloys including hastaloy, waspaloy, inconel, titanium, carbide, polycrystalline diamond compacts and conductive ceramics.
2. Which of the following does not hold true about wire cut EDM?
a) The electrode wire touches the workpiece while cutting the workpiece material
b) It can machine any electrically conductive material irrespective of its hardness
c) The di-electric fluid gets ionized in between the tool-electrode gap
d) During machining, the electrode wire does not get heated
Explanation: The wire does not touch the workpiece, so there is no physical pressure imparted on the workpiece compared to grinding wheels and milling cutters.
3. Which of the following is true about wire cut EDM?
a) Minimal clamping forces are required to hold the workpieces
b) It is a conventional process
c) It can machine materials like fibres, plastics, wood, etc
d) Electrodes used in die sink EDM and wire cut EDM are same
Explanation: The amount of clamping pressure required to hold small, thin and fragile parts is minimal, preventing damage or distortion to the workpiece.
4. Which of the following is true about wire cut EDM?
a) It leaves no residual burrs
b) It cannot machine materials having hardness beyond 20 BHN
c) It has poor accuracy as compared to milling
d) It uses petroleum products as di-electric fluid
Explanation: The EDM process leaves no residual burrs on the workpiece, which reduces or eliminates the need for subsequent finishing operations which indeed reduces the overall machining cost.
5. Large scale wire cut EDM machines can handle workpieces weighing upto _____ pounds.
Explanation: Wire cut EDM machines are manufactured in various sizes and styles of flush or submerged type machines to fit the needs of the consumer. Large scale machines can handle workpieces weighing over ten thousand pounds and can cut over twenty inches thick.
6. Wire cut EDM process can cut tapers of _____ degrees.
Explanation: In addition to the X-Y table travels, wire EDM’s have U / V travels for providing the movement to cut tapers. Most machines can cut tapers of 20-30 degrees depending on workpiece thickness.
7. Wire cut EDM machines work on _____ current.
c) both direct and alternating
Explanation: In wire EDM, the conductive materials are machined with a series of electrical discharges (sparks) that are produced between an accurately positioned moving wire (the electrode) and the workpiece. High frequency pulses of alternating or direct current are discharged from the wire to the workpiece with a very small spark gap through an insulated dielectric fluid.
8. The heat of each electrical spark generated during machining is around_____ Fahrenheit
a) 1,000° to 2,000°
b) 1,100° to 5,000°
c) 10,000° to 12,000°
d) 15,000° to 21,000°
Explanation: The heat of each electrical spark, estimated at around 15,000° to 21,000° Fahrenheit, which erodes away a tiny bit of material that is vaporized and melted from the workpiece.
9. The de-ionised water is used for flush away the burr as well as to cool the workpiece.
Explanation: The particles (chips) generated during machining are flushed away from the cut with a stream of de-ionized water through the top and bottom flushing nozzles. The water also prevents heat build-up in the workpiece. Without this cooling, thermal expansion of the part would affect the size and positional accuracy.
10. In wire cut EDM, machine movement is accomplished with precision lead screws with recirculating ball bearings.
Explanation: Machine movement is accomplished with precision lead screws with recirculating ball bearings on all axes that are driven by AC motors. Before shipping, the machine’s position is checked and any errors or backlash are corrected by pitch error compensation that is permanently stored in the computer’s memory.
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