This set of Manufacturing Processes Multiple Choice Questions & Answers (MCQs) focuses on “Wire-cut EDM – 7”.
1. 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
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.
2. The U and V axes provide movement to the wire to produce taper angles upto _____ degrees.
b) +/- 20
c) +/- 30
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.
3. 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
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.
4. The function of independent programming of the U & V axes in wire cut EDM machines is for _______
a) hexagonal workpieces
b) fullerene shaped workpieces
c) workpieces having a different shape on the top and bottom
d) workpieces having intricate shapes
Explanation: Wire cut EDM machines have U / V travels for providing the movement to cut tapers. Independent programming of the U & V axes is for workpieces that have a different shape on the top and bottom.
5. Which of the following is not machined by wire cut EDM?
b) extrusion dies
c) square shaped objects
d) perforated sheets
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.
6. How many sections does the di-electric system includes?
Explanation: The dielectric system includes:
• the water reservoir
• filtration system
• de-ionization system
• water chiller unit.
7. While machining, the dirty water is filtered through a _____
a) paper filter
b) notch filters
c) comb filters
d) fir filters
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.
8. 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
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.
9. A water chiller is used to keep _____ thermally stable.
a) electrode wire
b) electrode coils
c) control arms
d) dielectric reservoir
Explanation: A water chiller is provided as standard equipment to keep following systems thermally stable:
• the dielectric
• control arms
10. During the cutting process water conductivity level changes due to eroded chips.
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.
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