250+ TOP MCQs on Electron Beam Machining – 4 and Answers

Manufacturing Processes Multiple Choice Questions on “Electron Beam Machining – 4”.

1. In electron beam machining, the plane of _____ is on the surface of the workpiece.
a) focusing
b) finishing
c) heating
d) drilling
Answer: a
Clarification: The plane of focusing would be on the surface of the workpiece or just below the surface of the workpiece. This controls the kerf shape or the shape of the hole.

2. _____ can manoeuvre the electron beam.
a) Nozzles
b) Magnetic lens
c) Electromagnetic coils
d) Deflector coils
Answer: d
Clarification: In electron beam gun assembly, the final deflection coil can manoeuvre the electron beam which helps in generating holes of non-circular cross-section as required.

3. Electron beam machining process can machine holes of diameters in the range of _____
a) 10 μm to 80 μm
b) 50 μm to 100 μm
c) 100 μm to 2 mm
d) 2 mm to 5 mm
Answer: c
Clarification: Electron beam machining can provide holes of diameter in the range of 100 μm to 2 mm with a depth up to 15 mm, i.e., with a length/diameter ratio of around 10.

4. Which of the following is true about electron beam machining (EBM)?
a) By EBM process, tapered holes can be generated
b) Electro-magnetic coils are used to change the direction of the electron beam
c) Electron beam gun works under high pressure
d) Increasing the current density increases the spot size
Answer: a
Clarification: Electron beam machining can generate a hole which can be tapered along the depth or barrel shaped. By focusing the beam below the surface a reverse taper can also be obtained.

5. Which of the following holds true for electron beam machining?
a) This process does not generate burr
b) Holes having length/diameter ratio as high as 50 can be machined by this process
c) In electron beam gun, magnetic lens is used to diverge the beam
d) Electron beam is accelerated by electromagnetic coils
Answer: a
Clarification: Generally burr formation does not occur in electron beam machining. There would be an edge rounding at the entry point along with a presence of recast layer. Also, magnetic lens is used to focus the beam at a single point. Annular anodes are used to accelerate the beam.

6. Which of the following materials is not machined by the EBM process?
a) Titanium
b) Wood
c) Plastic
d) Leather
Answer: b
Clarification: Materials which can be machined by EBM are:
• Commercial grade steel
• Stainless steel
• Ti and Ni super alloys
• Aluminium plastics
• Ceramics
• Leathers.

7. For EBM process, heat affected zone is about _____
a) 10 μm to 80 μm
b) 20 μm to 30 μm
c) 100 μm to 1 mm
d) 2 mm to 5 mm
Answer: b
Clarification: In electron beam machining, the heat-affected zone is rather narrow due to the shorter pulse duration. Typically, the heat affected zone is around 20 μm to 30 μm.

8. Which of the following materials are easy to a machine by EBM process?
a) Aluminium
b) Steel
c) Plastic
d) Wood
Answer: a
Clarification: EBM can machine steel titanium alloys, aluminium, plastics, nickel alloys, etc., but some of the materials like Al and Ti alloys are more readily machined compared to steel.

9. Number of holes drilled per second depends on the holes diameter.
a) True
b) False
Answer: a
Clarification: Number of holes drilled per second depends on:
• hole diameter
• power density
• depth of the hole
• material type.

10. While machining, there are chances of thermal damage associated with EBM.
a) True
b) False
Answer: a
Clarification: As the mechanism of material removal is thermal in nature as for example in electro-discharge machining, there would be thermal damages associated with EBM. On the contrary, heat affected zone is narrow.