# Engineering Metrology Questions and Answers – Three Dimensional Measuring Machine

This set of Engineering Metrology Multiple Choice Questions & Answers (MCQs) focuses on “Three Dimensional Measuring Machine”.

1. Which of the following is provided as scales in three dimensional measuring machines?
a) Laser interferometer
b) Straight edge
c) Vernier caliper
d) Screw gauge

Explanation: Laser interferometers are provided as scales in three dimensional measuring machines. A cooling system is also provided in this machine. This cooling system is to reduce the temperature rise when it is in operation.

2. Which motor is used to control axes movement in three dimensional measuring machines?
a) Tachometer
b) Torque motor
c) Induction motor
d) Stepping motor

Explanation: Axes movement in three dimensional measuring machines is controlled by stepping motors. Stepping motors are attached to lead-screws. 3 carriages are provided and mounted upon double V-ways.

3. Which material is used for the base in three dimensional measuring machines?
a) Steel
b) Aluminium
c) Granite

Explanation: The machine base and metrology system should be made independent of each other. The external forces upon the metrology system should be constant. Granite is chosen for building the machine base because of low coefficient of expansion.

4. How many pneumatic isolators are used to support the base of three dimensional measuring machines?
a) 1
b) 2
c) 3
d) 4

Explanation: Three dimensional measuring machine has pneumatic isolators. The base of the machine is supported on 3 pneumatic isolators. The frame of a machine is built of steel because temperature-controlled oil shower is included.

5. Which of the following is true about electronic gauge stylus used in three dimensional measuring machines?
a) It is ball tipped
b) Tip is trapezoidal
c) Polygonal tip
d) Pointed tip

Explanation: The electronic gauge stylus is ball-tipped. It is a single axis, linear variable displacement transducer carried and positioned by the vertical or we can say ‘z’ slide. The axis of the linear variable displacement transducer is mounted at a 45 degree angle w.r.t the y and z axes.

6. How many laser interferometers are provided on y-axis slide?
a) 1
b) 2
c) 3
d) 4

Explanation: Two laser interferometers are provided on the y-axis slide. These are suitably separated. The difference in readings taken by these 2 lasers is used as a servo input to drive a piezoelectric crystal.

7. Which mounts are used to support frame?
a) Effective mounts
b) Dynamic mounts
c) Static mounts
d) Kinematic mounts

Explanation: Kinematic mounts are used to support the frame inside the machine base. The plane of the supports is coincident with the bending neutral axis of the machine base. Its influence is thereby minimized on the metrology frame.

8. Which drive is used in slide drive system present in three dimensional measuring machines?
a) Rack and pinion drive without gear teeth
b) Rack and pinion drive with gear teeth
c) Worm and worm gear drive without teeth
d) Worm and worm gear drive with teeth

Explanation: A portion of each bearing is evacuated and acts like a vacuum chuck to hold the bearing. The bearing surface balance provides lift. The slide drive system used in three dimensional measuring machines can be considered as a rack and pinion drive without gear teeth.

9. Which of the following option is true for given statements about 3-dimensional measuring machines?
Statement 1: A cooling system is present in 3-dimensional measuring machine.
Statement 2: It is designed for 3-dimensional calibration but not adaptable for computer control.
a) T, T
b) F, F
c) F, T
d) T, F

Explanation: Three dimensional measuring machines are useful in modern sophisticated industry. 3-D measuring machines are designed for 3-dimensional calibration. This machine is also adaptable for computer control.

10. Which type of error is introduced when the travel direction of LVDT is not normal to the part surface?
a) Sine error
b) Cosine error
c) Tangent error
d) Cotangent error

Explanation: When the direction of travel of Linear variable displacement transducer is not normal to the part surface, the cosine error is introduced. A correction is provided in this machine for this cosine error.

11. Which type of pathways is used for laser interferometer present in three dimensional measuring machines?
a) Helium unshielded pathways
b) Neon unshielded pathways
c) Helium shielded pathways
d) Neon shielded pathways

Explanation: Displacement accuracy is achieved by laser interferometers. Laser interferometers are operated in helium-shielded pathways. The interferometers are located in strict accordance with the Abbe principle.

Sanfoundry Global Education & Learning Series – Engineering Metrology.

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