GOVERNMENT ENGINEERING COLLEGE
VII SEM. ( EIC)
COLLEGE NO. 08EI28
Established in 1907 by J.N.Tata.
Formerly known as TATA IRON AND STEEL
World’s 6th Largest Steel making company.
28.1 million p.a. of crude steel production
Products: Steel, Blast furnaces,EOT cranes,
Automobiles, Machines etc.
Headquartered in Jamshedpur, Jharkhand and
registered office in Mumbai ,India
INTRODUCTION OF NC AND CNC
NC stands for Numerical Control
CNC is self contained NC system with a
Control a machine by programs or set of
Widely used for manufacturing system like
Machine Tools, Welders, And Laser Beam
Motivation and Uses
To manufacture complex curved geometries
in 2D or 3D was extremely expensive by
Machining components with repeatable
Unmanned machining operations
Easier to program
Easy storage of existing
Easy to change a program
Avoids human errors
NC machines are safer to operate
Complex geometry is produced
as cheaply as simple ones
Usually generates closer
tolerances than manual machines
Increase in electrical
Increase in initial investment.
Training of existing workforce.
Not cost-effective for low-level
production on simple parts
CNC SYSTEM ELEMENTS
A typical CNC system consists of the
following six elements
Program input device
Machine control unit
OPERATIONAL FEATURES OF CNC
A part program is a series of coded
instructions required to produce a part as
in the following example
N10 G01 X5.0 Y2.5 F15.0
| | | | |
| | | | Feed rate (15 in/min)
| | | Y-coordinate (2.5")
| | X-coordinate (5.0")
| Linear interpolation mode
Block is the smallest part of the programme.
The block is composed of words and always
ends with the characters “END OF BLOCK”.
A block contains the following WORDS :
Sequence / Block number __________________________ N
Preparatory Functions _____________________________ G
Dimensions _____________________________________ X, Y, Z
Arc Center Offset _________________________________ I, J, K
Feed Function ___________________________________ F
Speed Function __________________________________ S
Tool Function ____________________________________ T
Miscellaneous Function ____________________________ M
PROGRAM INPUT DEVICE
The program input device is the
mechanism for part programs to be
entered into the CNC control.
The most commonly used program input
devices are keyboards, punched tape
reader, throgh RS 232 serial ports and
MACHINE CONTROL UNIT
It is used to perform the following
Read coded instructions
Decode coded instructions
Implement interpolations (linear, circular,
and helical) to generate axis motion
Feed axis motion commands to the amplifier
circuits for driving the axis mechanisms
Receive the feedback signals of position and
speed for each drive axis
Implement auxiliary control functions such
as coolant or spindle on/off, and tool change
TYPES OF CNC CONTROL
A drive system consists of :
stepping motors or servomotors
Open Loop v/s Closed Loop controls
Elements of CNC machines
1. Terminal Connector (TC)
The Terminal Box provides easy, reliable connections
for wires and cables
3. Limit Switches
Interlocks a mechanical motion or
position with an electrical circuit.
Most common limit switch is the
single-pole contact block with
one NO and one NC set of
4. PUSH BUTTONS
controlling a process.
Colour coded: red(stop)
Used for switching a power
circuit of higher ampere
driving force to close the
Enclosed in insulating
material for protection.
• Learned about the basic electrical
• Learn different circuits used in CNC
• Introduction to CNC machine.
• Basic programming of CNC machine.