Question 1
_____ grades wire are used in automatic re-threading mechanisms.
A. Malleable
B. Softer
C. Harder
D. Commercial
View Answer
Answer: Option C
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.
Question 2
_____ is/are used as di-electric fluid in die sink EDM process.
A. Pure water
B. Silicone gel
C. Petroleum products
D. Epoxy resins
View Answer
Answer: Option C
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.
Question 3
A water chiller is used to keep _____ thermally stable.
A. electrode wire
B. electrode coils
C. control arms
D. dielectric reservoir
View Answer
Answer: Option C
Explanation:
A water chiller is provided as standard equipment to keep following systems thermally stable:• the dielectric• workpiece• worktable• control arms• fixtures.
Question 4
A thin metallic wire used in wire-cut EDM is kept submerged in a tank of _____
A. dielectric fluid
B. pure water
C. molten metal
D. kerosene
View Answer
Answer: Option A
Explanation:
The Wire Electric Discharge Machining (WEDM) is a variation of EDM and is commonly known as wire-cut EDM or wire cutting. In this process, a thin metallic wire is fed onto the workpiece, which is submerged in a tank of dielectric fluid such as deionized water.
Question 5
After a wire break, the wire tip segment that was clamped is disposed off in a wire tip disposal unit.
A. TRUE
B. FALSE
View Answer
Answer: Option A
Explanation:
The wire tip segment that was clamped is disposed of in a wire tip disposal unit. The supply wire is then directed into the lower guide. The wire then proceeds to the back of the machine where it is discarded in a scrap wire bin.
Question 6
After originating from a supply spool, the wire is passed through _____
A. a chamber filled with special stones
B. diamond guides
C. a furnace
D. a container filled with anti-oxidant
View Answer
Answer: Option B
Explanation:
After originating from a supply spool, the wire then passes through a set of precision, round diamond guides, and is then transported into a waste bin. The wire can only be used once, due to it being eroded from the EDM process.
Question 7
Copper is not used for making electrode wires in wire cut EDM because of its _____
A. Good conductivity
B. lower tensile strength
C. high melting point
D. higher purchasing cost
View Answer
Answer: Option B
Explanation:
The low tensile strength of copper wire made it subject to wire breaks when too much tension was applied. Poor flushability was another problem, due to coppers high thermal conductivity. A good portion of the heat from the EDM spark was transferred to the wire and carried away from the workzone instead of using that heat to melt and vaporize the workpiece.
Question 8
Di-electric system used in WEDM process is similar to that of the _____ process.
A. conventional drilling
B. conventional milling
C. conventional EDM
D. broaching
View Answer
Answer: Option C
Explanation:
The power supply and the di-electric system used in WEDM is very similar to that of the conventional EDM. The main difference lies only in the type of di-electric used.
Question 9
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
View Answer
Answer: Option A
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.
Question 10
During the cutting process water conductivity level changes due to eroded chips.
A. TRUE
B. FALSE
View Answer
Answer: Option A
Explanation:
During the cutting process the chips from the material that is being eroded, gradually changes the water conductivity level. Resistivity levels of the water are set according to the cutting requirements of the workpiece material being machined.
Question 11
During the WEDM process, workpiece undergoes a number of thermal cycles.
A. TRUE
B. FALSE
View Answer
Answer: Option A
Explanation:
In WEDM process, the selection of process parameters is very crucial, as in some cases the workpiece undergoes significant thermal cycles the can be very severe. These thermal cycles can form recast layers and induce residual tensile stresses on the workpiece.
Question 12
During the wire cut EDM process, the feature of adjustable tapering values is useful for _____
A. circular workpieces
B. mould applications
C. thick workpieces
D. forging dies
View Answer
Answer: Option B
Explanation:
Tapering values can be changed within the program. This is useful for mold applications or form tools that have different side and frontal taper relief angles. Die blocks are normally machined first with their taper relief, then straight cut for their die land.
Question 13
During wire cut EDM, the size of the cavity produced by the wire while machining depends upon _____
A. material of the workpiece
B. di-electric fluid used
C. wire material
D. electric current
View Answer
Answer: Option D
Explanation:
While machining a high electric current passes through the dielectric fluid and heats the workpiece surface from a very small area. The corresponding workpiece area melts and what is left, is a small round cavity. The cavity size depends on the electric current and potential.
Question 14
Electrically conductive materials are cut by WEDM process by _____ mechanism.
A. thermal
B. electro-thermal
C. electro-dynamic
D. fused metal
View Answer
Answer: Option B
Explanation:
Electrically conductive materials are cut by WEDM process by an electro-thermal mechanism. In the WEDM process, the motion of the wire is slow. It is fed in the programmed path and material is removed from the workpiece accordingly.
Question 15
For machining of high melting point materials, _____ wires are used.
A. gallium
B. zinc coated
C. aluminium coated
D. silver
View Answer
Answer: Option B
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.
Question 16
For manufacturing of complex shapes, soft electrode wires are used.
A. TRUE
B. FALSE
View Answer
Answer: Option A
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.
Question 17
For which of the following materials wire-cut EDM is not used?
A. Aluminium
B. Zirconium
C. Steels
D. Titanium
View Answer
Answer: Option B
Explanation:
Wire-cut EDM is used for cutting:• Aluminium• Brass• Copper• Graphite• Steels• Titanium.
Question 18
How many sections does the di-electric system includes?
A. 2
B. 3
C. 4
D. 5
View Answer
Answer: Option C
Explanation:
The dielectric system includes:• the water reservoir• filtration system• de-ionization system• water chiller unit.
Question 19
How many subsystems are there in wire-cut EDM process?
A. 2
B. 3
C. 4
D. 5
View Answer
Answer: Option C
Explanation:
The subsystems of Wire-EDM process are:• Power supply• Di-electric system• Wire feeding system• Positioning system.
Question 20
How many ways are there for making the fixed cores by wire cut EDM process?
A. 2
B. 3
C. 4
D. 5
View Answer
Answer: Option A
Explanation:
Basically there are two options for making the fixed cores:− Machine the cores directly to the mould insert plate or mould plate− Machine the cores to separate pieces of mould steel and attach the piece to the mould assembly.
Question 21
If there is a wire break during machining, the machine returns to the start point.
A. TRUE
B. FALSE
View Answer
Answer: Option A
Explanation:
If there is awire break during machining, the machine returns to the start point of that opening, re-threads the wire and move through the program path to the position where it broke, powers up, and continues cutting as if the wire had never broken.
Question 22
In a wire break situation, the end of the wire is_____ while the supply wire is _____
A. clamped, drawn back
B. drawn back, clamped
C. dipped in the di-electric fluid, clamped
D. welded with the other wire, drawn back
View Answer
Answer: Option A
Explanation:
The threading process of the automatic wire threader takes place automatically if there is a broken wire or by a command in the program. In a wire break situation, the end of the wire is clamped while the supply wire is drawn back, annealing and separating the wire, while leaving a sharp point on the end of the supply wire.
Question 23
In a wire cut EDM machine, _____ is used to control the resistivity of the de-electric fluid (water).
A. resin beds
B. water reservoir
C. de-ionisation system
D. diamond guides
View Answer
Answer: Option A
Explanation:
Following filtration, the clean water is measured for conductivity, and if required passes through a vessel that contains a mixed bed of anion and cation beads. This mixed bed resin (the ion exchange unit) controls the resistivity of the water to set values automatically.
Question 24
In the wire-cut EDM process, de-ionizing units are used for controlling the _____
A. feed rate
B. resistivity
C. burr formation
D. temperature of the wire
View Answer
Answer: Option B
Explanation:
In the wire-cut EDM process, water is commonly used as the dielectric fluid. Filters and de-ionizing units are used for controlling the resistivity and other electrical properties.
Question 25
In the wire-cut EDM process, water is also used for _____
A. cooling
B. increasing the feed rate
C. flushing away the burr
D. controlling the cutting speed
View Answer
Answer: Option C
Explanation:
Apart from being used as a dielectric fluid, the water also helps in flushing away the debris from the cutting zone. The flushing also helps to determine the feed rates to be given for different thickness of the materials.
Question 26
In WEDM, the wire is held tight between_____
A. upper and lower nozzles
B. upper and lower diamond guides
C. upper and lower groves in the handle
D. upper and lower pulleys
View Answer
Answer: Option B
Explanation:
In wire-cut EDM (WEDM), the wire which is constantly fed from a spool, is held between upper and lower diamond guides. The guides are usually CNC-controlled and move in the x–y plane.
Question 27
In wire cut EDM machine, _______ axes are positioned away from the work area to avoid moisture and contamination.
A. X and Y
B. X and Z
C. U and V
D. Y and V
View Answer
Answer: Option C
Explanation:
The rigid U and V axis is positioned away from the work area to avoid moisture, contamination and deflection from the high pressure flush. Most Wire EDM’s are equipped with a programmable “Z” axis giving precise control of the upper guide assembly to ensure accurate tapers.
Question 28
In wire cut EDM, machine movement is accomplished with precision lead screws with recirculating ball bearings.
A. TRUE
B. FALSE
View Answer
Answer: Option A
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.
Question 29
In wire-cut EDM process, material removal takes place by a series of discrete discharges between _____
A. di-electric fluid and the wire electrode
B. the wire-electrode and the workpiece
C. the workpiece and the CNC-table
D. wire electrodes
View Answer
Answer: Option B
Explanation:
In wire-cut EDM process, material removal takes place by a series of discrete discharges between the wire and the workpiece in the presence of a di-electric fluid. Water is commonly used as the di-electric fluid.
Question 30
In wire-cut EDM, a moving wire is used to _____
A. remove the burr
B. cut complex outlines
C. melt the material
D. make the way for the di-electric fluid
View Answer
Answer: Option B
Explanation:
In wire-cut EDM, a moving wire is used to cut complex outlines and fine details in the required workpiece. The wire is wound on a spool and is kept in constant tension.
Question 31
Large scale wire cut EDM machines can handle workpieces weighing upto _____ pounds.
A. 100
B. 600
C. 1000
D. 10000
View Answer
Answer: Option D
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.
Question 32
Selection of the wire is based on how many factors?
A. 2
B. 3
C. 4
D. 5
View Answer
Answer: Option C
Explanation:
The selection of wires is dependent on the following factors:• Cutting speeds (for good cutting speeds, coated wires are used)• Taper angles to be machined• Tensile strength (for cutting thick workpieces, wires of high tensile strengths are used)• Flushability.
Question 33
Submerged cutting helps cutting the workpieces without hampering the flush.
A. TRUE
B. FALSE
View Answer
Answer: Option A
Explanation:
Cutting round stock or tubing presents a combination of adverse effects. Submerged cutting can efficiently cut these jobs without the flush being impaired.
Question 34
Submerged machining is extremely useful for applications that generally have_____
A. poor flushing conditions
B. intricate shapes
C. tapered sections
D. good weldability
View Answer
Answer: Option A
Explanation:
Submerged machining is extremely useful for applications that generally have poor flushing conditions. Applications where poor flushing conditions exist are numerous.
Question 35
Submerged machining is used for ____
A. cutting small taper angles
B. tiny workpieces
C. laminations
D. workpieces with no undercuts
View Answer
Answer: Option C
Explanation:
Some applications and examples where submerged machining is more practical would be cutting large taper angles, tall workpieces, laminations, tubes, irregular shaped parts, workpieces with undercuts and cutting very close to the edge of the workpiece.
Question 36
The absolute minimum inner corner radius is _____
A. the wire radius minus the sparking gap width
B. the sparking gap width minus the wire radius
C. the wire radius plus the sparking gap width
D. double of the wire radius
View Answer
Answer: Option C
Explanation:
The absolute minimum inner corner radius is the wire radius added with the sparking gap width. Therefore during machining, the shapes produced have larger dimensions as compared to the shapes mentioned in the program.
Question 37
The automatic wire threading offers the ability to cut multiple openings in a workpiece without operator intervention.
A. TRUE
B. FALSE
View Answer
Answer: Option A
Explanation:
This feature allows multiple openings to be cut in die blocks, progressive dies, production, and prototype workpieces automatically and unattended without the intervention of an operator, resulting in higher productivity. The demand for automatic wire threading (AWT) and dependent reliability has been met with new and improved designs.
Question 38
The burr or cut particles are flushed away by the______
A. electrode
B. motion of the workpiece
C. di-electric fluid
D. coolant
View Answer
Answer: Option C
Explanation:
The area wherein discharge takes place gets heated to very high temperatures such that the surface gets melted and removed. The cut particles (debris) get flushed away by the continuously flowing dielectric fluid.
Question 39
The electrode wires are usually made form _____
A. graphite
B. iron
C. nickel
D. brass
View Answer
Answer: Option D
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.
Question 40
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°
View Answer
Answer: Option D
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.
Question 41
The materials which are not stress-relieved before machining by WEDM process can get distorted during machining.
A. TRUE
B. FALSE
View Answer
Answer: Option A
Explanation:
If the energy/power pulse is relatively low (as in finishing operations), little changes in the mechanical properties of the material are expected due to residual stresses. The components which are not stress-relieved earlier can get distorted in the machining process.
Question 42
The only difference between die-sink EDM and wire cut EDM is the _____
A. way of material removal
B. electrode used for the machining
C. type of materials machined
D. processing time
View Answer
Answer: Option B
Explanation:
In the die-sink EDM method the electrode has the same shapes as the wished machining results. In the wire cut EDM method the electrode is a moving wire made from some electrically conducting material. The workpiece is cut with the electrode wire.
Question 43
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
View Answer
Answer: Option B
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.
Question 44
The U and V axes provide movement to the wire to produce taper angles upto _____ degrees.
A. 15
B. #ERROR!
C. #ERROR!
D. 45
View Answer
Answer: Option C
Explanation:
These axes provide movement to the top portion of the wire to produce taper angles of up to +/- 30 degrees. Both conical and oblique cylindrical radii can be programmed, and the size of the top and bottom radii of the part can also be programmed.
Question 45
The upper guide can move independently about_____
A. x-axis
B. y-axis
C. x-y-w axes
D. z-u-v axes
View Answer
Answer: Option D
Explanation:
On most machines, the upper guide can move independently about the z–u–v axes, giving it the flexibility to cut tapered and transitioning shapes (example: square at the bottom and circle on the top).
Question 46
The WEDM process requires _____
A. lower initial investment
B. lesser cutting forces
C. a skilled operator
D. a coolant pump
View Answer
Answer: Option B
Explanation:
The wire-cut EDM process requires lesser cutting forces in material removal; hence it is generally used when lower residual stresses in the workpiece are desired.
Question 47
The wire ED machines have _____ programmable axes.
A. 2
B. 2-5
C. 6
D. 3-9
View Answer
Answer: Option B
Explanation:
The wire cut EDM machines have 2 – 5 programmable axes. The machines that are used in mould making applications typically have 5 programmable axes. These axes are Wire guide, wire tilting in x and y –directions and workpiece or wire system movements in x and y –directions.
Question 48
The wire EDM process is used for making moulds with high drafted walls.
A. TRUE
B. FALSE
View Answer
Answer: Option A
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.
Question 49
There is a greater risk of breaking a wire if ______
A. temperature of the wire is too high
B. larger taper angles are to be cut
C. the flush is not set properly
D. there is an inadequate flow of di-electric fluid
View Answer
Answer: Option C
Explanation:
There is a greater risk of breaking a wire if the flush is not set properly or if too much power is used. This condition is greatly reduced when cutting the part submerged.
Question 50
WEDM process can be used for cutting hard extrusion dies.
A. TRUE
B. FALSE
View Answer
Answer: Option A
Explanation:
This process is used in the following areas:• Aerospace, Medical, Electronics and Semiconductor applications• Tool & Die making industries.• For cutting the hard Extrusion Dies• In making Fixtures, Gauges & Cams.
Question 51
WEDM process can be used for manufacturing of micro-tools.
A. TRUE
B. FALSE
View Answer
Answer: Option A
Explanation:
Following are the few areas where WEDM process is used:• Cutting of Gears, Strippers, Punches and Dies• Manufacturing hard Electrodes• Manufacturing micro-tooling for Micro-EDM, Micro-USM and such other micromachining applications.
Question 52
The de-ionised water is used for flush away the burr as well as to cool the workpiece.
A. TRUE
B. FALSE
View Answer
Answer: Option A
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.
Question 53
The diameter of the electrode wire is in the range of _____
A. 0.001″ – 0.0035″
B. 0.003″ – 0.004″
C. 0.004″ – 0.014″
D. 0.020″ – 0.032″
View Answer
Answer: Option C
Explanation:
Wire diameters range from .004″ through .014″ with .010″ being the most commonly used. The wire originates from a supply spool, then passes through a tension device (different diameter wires require different amounts of tension to keep it straight). It then comes in contact with power feed contacts where the electric current is applied.
Question 54
The di-electric fluid gets ionizes in between _____ gap.
A. tool-electrode
B. cathode-anode
C. workpiece-electrode
D. tool-workpiece
View Answer
Answer: Option A
Explanation:
The di-electric fluid gets ionized in between the tool-electrode gap and hence, helps in creating a path for each discharge. Because of these discharges, material is removed from the workpiece.
Question 55
When it is not possible to have the flushing nozzles close to the top or bottom of the workpiece _____ machines may require constant adjustment of the top and bottom flush.
A. submerged type
B. splash flush
C. rigid flush
D. stock flush
View Answer
Answer: Option B
Explanation:
When it is not possible to have the flushing nozzles close to the top or bottom of the workpiece, splash flush machines may require constant adjustment of the top and bottom flush. When machining submerged, you can adjust the flush once and forget it.
Question 56
When parts with existing openings in them must be cut, conventional flushing produces _____
A. air pockets
B. unnecessary tapers
C. undercuts
D. poor flushing
View Answer
Answer: Option A
Explanation:
When parts with existing openings, slots or cross holes in them must be cut, conventional flushing produces air pockets and results in reduced performance or wire breaks. Submerged machining provides stable cutting of these parts.
Question 57
Which of the following component of the wire cut EDM machine does not get heated?
A. Workpiece
B. Electrode wire
C. Di-electric fluid
D. Coils
View Answer
Answer: Option B
Explanation:
The electrode wire moves between two coils with a moderate speed. The part of the wire that actually machines the workpiece is constantly changing. There is no time for the wire to heat up.
Question 58
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
View Answer
Answer: Option A
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.
Question 59
Which of the following is not machined by wire cut EDM?
A. airfoils
B. extrusion dies
C. square shaped objects
D. perforated sheets
View Answer
Answer: Option D
Explanation:
The independent, simultaneous movement of all four axes (X, Y, U, V) makes machining extrusion dies, airfoil shapes, and “squircles” (a square shape on the top, and a circle on the bottom of the workpiece) quite easy.
Question 60
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
View Answer
Answer: Option D
Explanation:
The most typical wire cut EDM applications in mould making are: −• Machining ejector holes• Shaping and cutting the ejector pin ends to follow mould cavity surface shapes• Machining cores and corresponding fastening holes in the mould plates and inserts.
Question 61
Which of the following is not the benefit of submerged cutting?
A. improved accuracy
B. better surface finish
C. Thermal stability
D. no wire breakage
View Answer
Answer: Option D
Explanation:
Benefits of submerged cutting are:• Enhanced thermal stability of the entire set up• Accurate skim cuts• Better surface finish• Improved accuracy.
Question 62
Which of the following is not the effect of less maintenance of the wire cut EDM machines?
A. Wire breaks
B. Lines in the part
C. Lowered time to complete the job
D. Rough surfaces
View Answer
Answer: Option C
Explanation:
the lack of maintenance will lead to slower cutting speeds, size inaccuracy, lines in the part, wire breaks, a rougher surface finish, and (eventually) a service call. Maintenance of Wire EDM machine (or any EDM machine) usually consumes twenty to thirty minutes a week or less.
Question 63
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
View Answer
Answer: Option A
Explanation:
The amount of clamping pressure required to hold small, thin and fragile parts is minimal, preventing damage or distortion to the workpiece.
Question 64
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
View Answer
Answer: Option A
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.
Question 65
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
View Answer
Answer: Option C
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.
Question 66
Which of the following material properties sets restrictions to use wire cut EDM?
A. Material type
B. Melting point
C. Material hardness
D. Electrical conductivity
View Answer
Answer: Option D
Explanation:
As the electrode wire does not get heated during machining, the problems with electrode wear are not an issue like in the case of die-sink ED machining and it is possible to use wire cut EDM also for materials with high melting ranges. The material hardness sets no restrictions. The only restriction is that the material needs to be electrically conductive.
Question 67
Which of the following materials is not machined by wire cut EDM?
A. Inconel
B. Graphite
C. Tool steel
D. Hastaloy
View Answer
Answer: Option D
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.
Question 68
Which of the following materials is not used for electrode wires?
A. Molybdenum
B. Brass
C. Steel
D. Graphite
View Answer
Answer: Option C
Explanation:
There is a vast array of wires to choose from with brass wire normally being used however, molybdenum, graphitized, and thick and thin layered composite wires are available for different applications.
Question 69
While machining, the dirty water is filtered through a _____
A. paper filter
B. notch filters
C. comb filters
D. fir filters
View Answer
Answer: Option A
Explanation:
During cutting, the dirty water is drained into the unfiltered side of the dielectric reservoir where the water is then pumped and filtered through a paper filter, and returned to the clean side of the dielectric tank.
Question 70
Wire cut EDM process can cut tapers of _____ degrees.
A. 5-10
B. 8-16
C. 20-30
D. 25-45
View Answer
Answer: Option C
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.
Question 71
Wire electric discharge (ED) machining is based on the same principle as that of _____
A. hydro-dynamic EDM
B. die-sink EDM
C. polar EDM
D. non-conventional EDM
View Answer
Answer: Option B
Explanation:
Wire electric discharge (ED) machining is based on the same principle as die-sink ED machining. The basic elements in all EDM methods are dielectric fluid, a workpiece and an electrode.
Question 72
Wire-cut EDM (WEDM) process is widely used for _____
A. alloy steels
B. tool steels
C. stainless steels
D. carbon steels
View Answer
Answer: Option B
Explanation:
WEDM is a non-conventional process and is very widely used in tool steels for a pattern and die making industries. The process is also used for cutting intricate shapes in components used for the electric and aerospace industries.
Question 73
Wire-cut EDM can cut plates of thickness upto _____
A. 50mm
B. 100mm
C. 300mm
D. 500mm
View Answer
Answer: Option C
Explanation:
Wire-cut EDM process can cut plates as thick as 300mm and is used for making punches, tools and dies from hard metals that are difficult to machine with other methods.
Question 74
Wires used in wire cut EDM are usually disposed after one usage.
A. TRUE
B. FALSE
View Answer
Answer: Option A
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.
Question 75
With the addition of the programmable _____ to wire cut EDM machine, workpieces of different thicknesses can be machined.
A. X-axis
B. Y-axis
C. Z-axis
D. chuck
View Answer
Answer: Option C
Explanation:
With the addition of the programmable “Z” axis, workpieces of different thickness, can also be machined. For example, the die openings and dowel pin holes can be machined on a one inch thick die block, then the machine can be programmed to move to another location and machine the punches on a two or three inch thick workpiece.