This set of CNC Multiple Choice Questions & Answers (MCQs) focuses on “Numerical Control”.
1. Numerical Control comes under which category of automation?
a) Fixed
b) Flexible
c) Hydraulic
d) Programmable
View Answer
Explanation: In Numerical Control, a program of instructions controls the machine tool or other equipment. The program can be altered for the next variety of job that requires a different sequence of operations.
2. A Numerical Control program consists of ______ codes.
a) Pictographic
b) Alphanumeric
c) Symbolic
d) Graphical
View Answer
Explanation: A program for Numerical Control is written in alphanumeric codes. The alphanumeric characters represent instructions to operate the machine and relative position of tool and work piece.
3. Which of the following is not a basic component of the Numerical Control system?
a) Part program
b) Machine control unit
c) Part programmer
d) Processing equipment
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Explanation: A Numerical Control system has three basic components- a part program of instructions, machine control unit, and processing equipment. The person who prepares the part program is known as a part programmer.
4. Earlier, the NC part program was written on which of the following medium?
a) Punched tape
b) Compact disc
c) Digital versatile disc
d) Memory cards
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Explanation: Earlier, the program for Numerical Control was written on 1 inch wide punched tape. Gradually the punched tape was replaced by the magnetic tape, diskette, and microcomputer. The part program is written in a standard format to be interpreted by the machine control unit.
5. The processing equipment consists of reading devices for entering the part program into memory?
a) True
b) False
View Answer
Explanation: Reading devices are part of the machine control unit. The machine control unit converts the command into mechanical actions of processing machine tool or equipment. Earlier, tape readers were used in Numerical Control systems.
6. Axis system for Numerical Control is based on which of the following coordinate system?
a) Spherical coordinates
b) Cylindrical coordinates
c) Cartesian coordinates
d) Polar coordinates
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Explanation: There are two axis systems used in Numerical Control to specify the position of work head relative to the work-piece. One of these is used for flat and prismatic parts and other for rotational parts.
7. Position of the tool relative to rotating work-piece is defined in the ____ plane in a rotational Numerical Control system.
a) x-z
b) x-y
c) y-z
d) angular
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Explanation: Rotational NC system is used for NC lathes, turning machines, etc. Y-axis is not used for defining the location in the rotational NC system. The x-axis gives the radial location of tool and z-axis is parallel to the rotational axis of work-piece.
8. ________ system move worktable to a specified location and has no concern with the path taken.
a) Linear control
b) Continuous path control
c) Point to point
d) Circular
View Answer
Explanation: A point to point system is used when operations are performed at discrete locations like drilling, spot welding, etc. The program consists of a series of point locations at which operations are performed.
9. Contouring is related to which of the following type of motion control system?
a) Point to point control
b) Polar path control
c) Cartesian path control
d) Continuous path control
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Explanation: When the continuous path control system is used to control two of more axes simultaneously, it is known as contouring. The term straight cut is used when the tool moves parallel to only one of the major axis of the work table.
10. Which of the following is not an NC interpolation method for continuous path control?
a) Linear interpolation
b) Parallel interpolation
c) Circular interpolation
d) Parabolic & cubic interpolation
View Answer
Explanation: Linear interpolation, circular interpolation, helical interpolation, and parabolic & cubic interpolation methods are used for continuous path control in Numerical Control machines. Linear interpolation is used for a straight path.
11. _________ positioning defines the work head position respective to the origin of the axis system.
a) Absolute
b) Relative
c) Incremental
d) Axial
View Answer
Explanation: There are two types of positioning systems. In absolute positioning, the work head location depends on the origin of the axis system. In incremental positioning, the work head location is defined relative to its present location.
12. Circular interpolation permits to define helical path in 3D space.
a) True
b) False
View Answer
Explanation: Helical interpolation involves circular interpolation for two axes with the linear movement of the third axis. It permits a helical path in 3D space. It is used for applications like machining large internal threads.
Sanfoundry Global Education & Learning Series – CNC.
To practice all areas of CNC, here is complete set of Multiple Choice Questions and Answers.
