McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Mechanical Engineering .
| 301. |
Wires used in wire cut EDM are usually disposed after one usage. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: despite the minimum wear, wires are usually disposed after one usage. sparking and high temperature during the machining reduces the wire tensile strength and the wire could easily break if re-used. | |
| 302. |
The electrode wires are usually made form |
| A. | graphite |
| B. | iron |
| C. | nickel |
| D. | brass |
| Answer» D. brass | |
| Explanation: wire used in wire cut edm are usually made of brass – either zinc-coated or uncoated. brass wire can be purchased in different hardnesses and different diameters. zinc coated wire is used in machining high melting point workpiece materials | |
| 303. |
grades wire are used in automatic re-threading mechanisms. |
| A. | malleable |
| B. | softer |
| C. | harder |
| D. | commercial |
| Answer» C. harder | |
| Explanation: the harder grades are used in automatic re-threading mechanisms and also if the machined shapes contain high flat surfaces. hard wires resist change in direction and for that reason are likely to produce nice flat surfaces. | |
| 304. |
For machining of high melting point materials, wires are used. |
| A. | gallium |
| B. | zinc coated |
| C. | aluminium coated |
| D. | silver |
| Answer» B. zinc coated | |
| Explanation: zinc coated wire is used in machining high melting point workpiece materials. the zinc coating vaporises in lower temperature than the brass core. vaporisation reduces the amount of heat that transmits to the brass and the core wears less. | |
| 305. |
is/are used as di-electric fluid in die sink EDM process. |
| A. | pure water |
| B. | silicone gel |
| C. | petroleum products |
| D. | epoxy resins |
| Answer» C. petroleum products | |
| Explanation: the dielectric fluid in the die-sink edm process is usually some petroleum product. in the wire cut edm process, it is most common to use de-ionised water. | |
| 306. |
Which of the following is not the application of wire cut EDM process? |
| A. | machining ejector holes |
| B. | cutting the ejector pins |
| C. | machining cores of various moulds |
| D. | machining of complex shapes made of plastic |
| Answer» D. machining of complex shapes made of plastic | |
| Explanation: the most typical wire cut edm applications in mould making are: − | |
| 307. |
During mould making by wire cut EDM, it is important to harden to counter the effects of changes in the shape of the workpiece due to heat treatment. |
| A. | the insert |
| B. | electrode wire |
| C. | electrode holding coils |
| D. | bolting points in the workpiece |
| Answer» A. the insert | |
| Explanation: it is important to harden the insert or mould plate steel before making the tightly tolerated ends in the ejector pin holes because the heat treatment tends to change the workpiece shapes at a certain degree. | |
| 308. |
Which of the following machining process is usually preferred for cutting of ejectors which are used in mould making? |
| A. | milling |
| B. | hobbing |
| C. | wire-cut edm |
| D. | die sink edm |
| Answer» C. wire-cut edm | |
| Explanation: there is a need to cut the ejector to a right dimension and if the cavity surface is shaped there is also a need to shape the ejector end. the wire ed machine is one of the most accurate machines in mould shops and usually there is also free machining time available. another option is to cut and shape the ejectors in a milling machine, but the most accurate milling machines are used in mould cavity machining operations and normally they are rather busy for long periods of time. | |
| 309. |
How many ways are there for making the fixed cores by wire cut EDM process? |
| A. | 2 |
| B. | 3 |
| C. | 4 |
| D. | 5 |
| Answer» A. 2 | |
| Explanation: basically there are two options for making the fixed cores: | |
| 310. |
The selection of the manufacturing process depends upon |
| A. | chemical reactivity between the mould material and the di-electric fluid |
| B. | mould shape |
| C. | application of the mould |
| D. | number of parts to be machined |
| Answer» B. mould shape | |
| Explanation: the selection depends on the core dimensions and shapes. high and narrow cores or cores with sharp shapes are easiest to manufacture with separate parts. special cases are core pins. core pins are used in making small diameter holes to castings. | |
| 311. |
The wire EDM process is used for making moulds with high drafted walls. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: like every wall in the mould opening direction, the core walls are also drafted. it is rather difficult to make high drafted walls with a milling machine. especially in the case of injection moulding or high pressure die casting moulds where the accuracy requirements are very high. the wire ed machine produces these shapes accurately with ease. | |
| 312. |
For manufacturing of complex shapes, soft electrode wires are used. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: soft wires are useful in applications with complex shapes, where the machine changes the wire tilting angle several times. the harder grades are used in automatic re- threading mechanisms | |
| 313. |
What is the full form of LBM in advanced machining processes? |
| A. | laser beam manufacturing |
| B. | laser beam machining |
| C. | light blast manufacturing |
| D. | light beam machining |
| Answer» B. laser beam machining | |
| Explanation: the full form of lbm is laser beam machining in the advanced machining processes. | |
| 314. |
LBM offers a good solution for which material properties below? |
| A. | thermal conductivity |
| B. | specific heat |
| C. | boiling temperature |
| D. | all of the mentioned |
| Answer» D. all of the mentioned | |
| Explanation: lbm offers good solution for material properties such as thermal conductivity, specific heat, melting and boiling temperatures. | |
| 315. |
What is the abbreviation of Laser? |
| A. | light allowed simple emission of radiation |
| B. | light amplification by stimulated emission of radiation |
| C. | light amplified simultaneous emission of rays |
| D. | light amplified stimulated emanation of rays |
| Answer» B. light amplification by stimulated emission of radiation | |
| Explanation: full form of laser is light amplification by stimulated emission of radiation. | |
| 316. |
Which of the following are the properties of a laser? |
| A. | highly collimated |
| B. | monochromatic |
| C. | coherent light beam |
| D. | all of the mentioned |
| Answer» D. all of the mentioned | |
| Explanation: highly collimated, high monochromaticity and the coherence of the light beam are the properties of a laser. | |
| 317. |
Laser beam machining uses which type of power sources for machining? |
| A. | very low power |
| B. | low power |
| C. | medium power |
| D. | high power |
| Answer» D. high power | |
| Explanation: high power densities are used for the generation of laser and for machining in laser beam machining. | |
| 318. |
Which of the following are different types of lasers used in Laser beam machining? |
| A. | solid-state ion |
| B. | neutral gas |
| C. | semiconductor |
| D. | all of the mentioned |
| Answer» D. all of the mentioned | |
| Explanation: laser such as solid-state ion, neutral gas, molecular, semiconductor etc.., can be used in lbm. | |
| 319. |
Which types of lasers are used in Laser beam machining? |
| A. | continuous wave |
| B. | pulsed mode |
| C. | continuous wave & pulsed mode |
| D. | none of the mentioned |
| Answer» C. continuous wave & pulsed mode | |
| Explanation: laser may be in continuous wave (cw) or in pulsed mode (pm) for machining in lbm. | |
| 320. |
What is the wavelength value of Ruby laser used in Laser beam machining? |
| A. | 633 nm |
| B. | 694 nm |
| C. | 856 nm |
| D. | 1064 nm |
| Answer» B. 694 nm | |
| Explanation: the value of wave length of ruby laser used in laser beam machining is 694 nm. | |
| 321. |
What is the wavelength value of Nd-YAG and Nd-glass lasers used in LBM? |
| A. | 633 nm |
| B. | 694 nm |
| C. | 856 nm |
| D. | 1064 nm |
| Answer» D. 1064 nm | |
| Explanation: the value of wave length of nd-yag and nd-glass lasers used in lbm is 1064 nm. | |
| 322. |
What is the wavelength value of neutral gas laser used in LBM? |
| A. | 633 nm |
| B. | 694 nm |
| C. | 856 nm |
| D. | 1064 nm |
| Answer» A. 633 nm | |
| Explanation: the value of wave length of neutral gas laser used in laser beam machining is 633 nm. | |
| 323. |
What is the wavelength value of CO2 laser used in Laser beam machining? |
| A. | 0.16 μm |
| B. | 1.6 μm |
| C. | 10.6 μm |
| D. | 106 μm |
| Answer» C. 10.6 μm | |
| Explanation: the value of wave length of co2 laser used in laser beam machining is 10.6 μm. | |
| 324. |
What is the material removal mechanism of Laser beam machining process? |
| A. | melt and evaporate |
| B. | electro chemical corrosion |
| C. | mechanical erosion of materials |
| D. | electro chemical dissolution |
| Answer» A. melt and evaporate | |
| Explanation: the material is removed by melting and evaporation in laser beam machining process. | |
| 325. |
Physics of laser is very complex due to which of the reasons below? |
| A. | scattering loss |
| B. | reflection loss |
| C. | scattering & reflection loss |
| D. | none of the mentioned |
| Answer» C. scattering & reflection loss | |
| Explanation: physics of laser is very complex because of scattering and reflection losses. | |
| 326. |
What happens when the heat is diffused into bulk material? |
| A. | phase change occurs |
| B. | melting occurs |
| C. | vaporization may take place |
| D. | all of the mentioned |
| Answer» D. all of the mentioned | |
| Explanation: the heat diffusion into bulk material causes phase change, melting or vaporization in the materials. | |
| 327. |
What happens to the process efficiency if plasma plumes are formed in LBM? |
| A. | increases |
| B. | enhances |
| C. | decreases |
| D. | improves |
| Answer» C. decreases | |
| Explanation: in laser beam machining, the process efficiency is reduced due the absorption and scattering loses when plasma plumes are formed. | |
| 328. |
Machining of LBM takes place when power density is than what is lost by conduction and radiation. |
| A. | greater |
| B. | smaller |
| C. | lower |
| D. | same as |
| Answer» A. greater | |
| Explanation: machining of laser takes place when power density is greater than what is lost by conduction, convection and radiation. | |
| 329. |
Which of the following phenomenon take place before melting and evaporating in LBM? |
| A. | conduction |
| B. | reflection |
| C. | absorption |
| D. | all of the mentioned |
| Answer» D. all of the mentioned | |
| Explanation: material in lbm is removed through several effects such as conduction, absorption, reflection following melting and evaporation. | |
| 330. |
What happens to the material removal rate when reflectivity is higher? |
| A. | will decrease |
| B. | will increase |
| C. | will enhance |
| D. | remains same |
| Answer» A. will decrease | |
| Explanation: in lbm, as the reflectivity of the metals is increased the material removal rates of the process are decreased. | |
| 331. |
Reflectivity of the materials depends on which of the following factors? |
| A. | wave length |
| B. | properties of material |
| C. | surface finish |
| D. | all of the mentioned |
| Answer» D. all of the mentioned | |
| Explanation: reflectivity of the materials depends on wavelength, the properties of materials, surface finish and temperature. | |
| 332. |
How much amount of incident radiation is reflected at lower power densities? |
| A. | 10 percent |
| B. | 20 percent |
| C. | 50 percent |
| D. | 90 percent |
| Answer» D. 90 percent | |
| Explanation: most of the metals reflect nearly 90 percent of incident radiation if the power densities are low. | |
| 333. |
How are minimum energies required for plastics when compared to that required for metals? |
| A. | lower than |
| B. | higher than |
| C. | same as |
| D. | none of the mentioned |
| Answer» A. lower than | |
| Explanation: the minimum energies required for plastic are lower than that required for metals. | |
| 334. |
Which of the following has high machining speeds in Laser Beam Machining? |
| A. | metals |
| B. | non metals |
| C. | metal alloys |
| D. | all of the mentioned |
| Answer» B. non metals | |
| Explanation: non metallic material machine at higher speeds than metallic ones due to higher reflectivity in metallic materials | |
| 335. |
Which of the following are the applications of Laser Beam Machining? |
| A. | drilling |
| B. | cutting |
| C. | texturing |
| D. | all of the mentioned |
| Answer» D. all of the mentioned | |
| Explanation: drilling, cutting and grooving, texturing and structuring, milling and dressing etc.., are the applications of laser beam machining process. | |
| 336. |
State whether the following statement is true or false regarding the drilling using LBM. “Compared to LBM, conventional machining is more accurate and efficient.” |
| A. | true |
| B. | false |
| Answer» B. false | |
| Explanation: conventional machining is less sufficient than laser beam machining because of their material toughness. | |
| 337. |
Other non-conventional processes lay behind Laser beam machining in drilling process because of which factors below? |
| A. | high cost |
| B. | long lead times |
| C. | low machining speeds |
| D. | all of the mentioned |
| Answer» D. all of the mentioned | |
| Explanation: other non-conventional processes need high costs for tools, long lead times, and low machining speeds when compared to lbm. | |
| 338. |
Laser drilling has proven to be more efficient in which of the following factors? |
| A. | cost |
| B. | quality |
| C. | reliability |
| D. | all of the mentioned |
| Answer» D. all of the mentioned | |
| Explanation: laser drilling has proven to be an efficient one in terms of cost, quality, and reliability for large-scale production applications. | |
| 339. |
Which of the following are different laser drilling processes in Laser beam machining? |
| A. | direct drilling |
| B. | drill and ream |
| C. | trepanning |
| D. | all of the mentioned |
| Answer» D. all of the mentioned | |
| Explanation: laser drilling can be performed by three methods that are – direct (percussion) drilling, trepanning, drill and ream. | |
| 340. |
The hole size in direct drilling depend up on which of the factors below? |
| A. | input power |
| B. | focusing adjustments |
| C. | input power & focusing adjustments |
| D. | none of the mentioned |
| Answer» C. input power & focusing adjustments | |
| Explanation: the hole size in the direct drilling method of laser drilling process, depend on input power and focusing adjustments. | |
| 341. |
Which method mentioned below is used for drilling of large size holes? |
| A. | direct drilling |
| B. | drill and ream |
| C. | trepanning |
| D. | all of the mentioned |
| Answer» C. trepanning | |
| Explanation: trepanning method of laser drilling process is used for drilling large holes either by rotating or moving the part. | |
| 342. |
What is the value the maximum optimum depth that can be machined using Laser drilling process? |
| A. | 0.17 mm |
| B. | 1.7 mm |
| C. | 17.1 mm |
| D. | 171.7 mm |
| Answer» B. 1.7 mm | |
| Explanation: the maximum depth obtained when by using laser drilling is about 1.7 mm. | |
| 343. |
What is the depth-to-diameter ratio obtained in drilling process using Laser beam machining? |
| A. | 10:1 |
| B. | 20:1 |
| C. | 50:1 |
| D. | 80:1 |
| Answer» C. 50:1 | |
| Explanation: value of the maximum depth-to-diameter ratio obtained in drilling using laser beam machining is 50:1. | |
| 344. |
What is the maximum value of drilling depth in trepanning method of laser drilling process? |
| A. | 1.7 mm |
| B. | 4.3 mm |
| C. | 6.4 mm |
| D. | 7.9 mm |
| Answer» C. 6.4 mm | |
| Explanation: the depth increases when we use a trepanning method for laser drilling process and that is about 6.40 mm. | |
| 345. |
What is the value of minimum corner radius obtained by drilling in Laser beam machining? |
| A. | 0.10 mm |
| B. | 0.25 mm |
| C. | 0.50 mm |
| D. | 0.65 mm |
| Answer» B. 0.25 mm | |
| Explanation: the value of the minimum corner radius obtained while drilling using lbm is about 0.25 mm | |
| 346. |
Peak power should be increased in Laser drilling process by pulse energy. |
| A. | increasing |
| B. | decreasing |
| C. | reducing |
| D. | constant |
| Answer» A. increasing | |
| Explanation: required peak power in the laser drilling process can be obtained by increasing the pulse energy while keeping the pulse duration constant. | |
| 347. |
Drilling of holes with larger pulse duration causes which effect to the holes produced? |
| A. | enlarge holes |
| B. | reduce hole size |
| C. | decrease the depth |
| D. | all of the mentioned |
| Answer» A. enlarge holes | |
| Explanation: drilling the holes with larger pulse duration causes enlargement of the hole entrance. | |
| 348. |
pulse energy and pulse duration are suitable for drilling. |
| A. | low, short |
| B. | low, long |
| C. | high, short |
| D. | high, long |
| Answer» C. high, short | |
| Explanation: in lbm, high energy pulses and low pulse duration are more suitable for hole drilling in aerospace materials. | |
| 349. |
Which of the following are the functions of assist gases? |
| A. | removal of molten material |
| B. | shield the lenses |
| C. | better efficiency |
| D. | all of the mentioned |
| Answer» D. all of the mentioned | |
| Explanation: assist are used to remove the molten material, it also shield the lenses from expelled material and they are also used for obtaining better process efficiencies. | |
| 350. |
Selection of assist gas depends on which of the following properties of work piece? |
| A. | material |
| B. | thickness |
| C. | material & thickness |
| D. | none of the mentioned |
| Answer» C. material & thickness | |
| Explanation: the selection of different assist gases depends on the work piece material and its thickness. | |
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