Manufacturing Processes Multiple Choice Questions on “Wire-cut EDM – 1”.
1. 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
Answer: a
Clarification: 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.
2. Wire-cut EDM can cut plates of thickness upto _____
a) 50mm
b) 100mm
c) 300mm
d) 500mm
Answer: c
Clarification: 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.
3. 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
Answer: b
Clarification: 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.
4. The upper guide can move independently about_____
a) x-axis
b) y-axis
c) x-y-w axes
d) z-u-v axes
Answer: d
Clarification: 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).
5. 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
Answer: b
Clarification: 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.
6. 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
Answer: c
Clarification: 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.
7. The WEDM process requires _____
a) lower initial investment
b) lesser cutting forces
c) a skilled operator
d) a coolant pump
Answer: b
Clarification: 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.
8. The materials which are not stress-relieved before machining by WEDM process can get distorted during machining.
a) True
b) False
Answer: a
Clarification: 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.
9. During the WEDM process, workpiece undergoes a number of thermal cycles.
a) True
b) False
Answer: a
Clarification: 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.
10. Electrically conductive materials are cut by WEDM process by _____ mechanism.
a) thermal
b) electro-thermal
c) electro-dynamic
d) fused metal
Answer: b
Clarification: 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.