# Engineering Metrology Questions and Answers – Numerical Controlled Coordinate Measuring Machines

This set of Engineering Metrology Questions and Answers for Campus interviews focuses on “Numerical Controlled Coordinate Measuring Machines”.

1. In which of the following numerical controlled CMM used?
a) Workshops
b) Production floors
c) Workshop and production floors both
d) Can be used anywhere

Explanation: CMMs are designed originally for the measurement of high-precision on relatively few workpieces in the metrology labs but are now used both in the workshop and on the production floor.

2. Which of the following technique is used to measure the profile of cams on numerical controlled CMM?
a) Scanning technique
b) Searching technique
c) Standing technique
d) Sorting technique

Explanation: The profile or form of cams and cutting dies, etc., can be measured on numerical controlled CMM by a scanning technique. This technique takes about 50 measurements and processes them every second.

3. Which of the following is responsible to control the processes in numerical controlled machines?
a) Symbols and letters
b) Letters and numbers
c) Numbers and symbols
d) Numbers, symbols and letters

Explanation: Numerical control is a programmable automation of machines and processes in which process is controlled by symbols, letters and numbers. In numerical control program, instruction changes when job changes.

4. Which type of probe system is used in CMM?
a) One dimensional probe system
b) Two dimensional probe system
c) Three dimensional probe system
d) Both one and two dimensional probe system

Explanation: Coordinate measuring machines both portable and bridge-type have a probe system. These probe systems have three dimensional probes which are suitable for dynamic measurements.

5. In CMMs adequate numbers of soft keys are present. What are soft keys?
a) Keys with variable functions
b) Keys not hard to press
c) Soft running keys so that less fatigue to operator
d) Keys made of soft material

Explanation: In CMMs which are installed with microprocessor based controls, suitable number of soft keys are provided. These keys are the keys with variable functions, which handle commands required for man-machine dialogue.
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6. Which of the following option is true for given statements about numerical controlled CMM?
Statement 1: Idle time of the production equipment is more.
Statement 2: Software for automatic evaluation is incorporated.
a) T, T
b) F, F
c) T, F
d) F, T

Explanation: In a numerical controlled coordinating measuring machine, software suitable for automatic calibration of the probe, calculation of geometric elements and automatic evaluation and recording is incorporated.

7. What is the use of SPC software in CMMs?
a) Dynamic analysis of measurement
b) Statistical analysis of measurement
c) System analysis of measurement
d) Quality analysis of measurement

Explanation: SPC software is a feature present in CMMs. It is for statistical analysis of measurements. Temperature compensation is also present for a change in the temperature due to various reasons like environmental change.

8. Which of the following is used to inspect nonlinear surfaces in very fast way in CMMs?
a) Laser triangulation probe
b) Impact protection
c) Wave lasers
d) Line laser

Explanation: Laser triangulation probes are used to scan the surface and after scanning it transmits a continuous flow of data. Line lasers are the fastest way to inspect non-linear surfaces. It is widely used in reverse engineering.

9. Which of the following is true for the given statements about numerical controlled CMM?
Statement 1: Command like full 3D alignment is provided.
Statement 2: Repeat function is used to simplify the inspection of features which are similar.
a) T, T
b) F, F
c) F, T
d) T, F

Explanation: Various commands are provided in CMMs. These commands are full 3-D alignment, multipoint measurement of circle centers, choice of 3 working planes, probe diameter compensation etc.

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