Numeric
Control
of
Machine
Tools
The word Numerical is defined as the expression of something by numbers.
The word control is defined as the exercise of directing, guiding or restraining power over something.
Thus, the word Numerical control consists of directing, guiding or restraining power over something by the use of numbers. Since numbers are merely symbols and letters are used also, numerical control could well be caned symbolic control.
Numerical
Control
of
Machine
Tools refers
to
the
operation
of
machine
tools
using
numerical
data
stored
on
paper
or
magnetic
tape,
tabulating
cards,
computer
storage
or
direct
information.
ASTME
defines
numerical
control
as
a
technique
for
automatically
controlling
machine
tools,
equipment
or
processes.
Numerical
control can
be
defined
as
a
form
of
programmable
automation
in
which
the
process
is
controlled
by
numbers,
letters
and
symbols
A
numerically
controlled
machine
tool
is
basically
a
con
ventional
machine
tool
where
the
operator
is
replaced
by
feedback
control
equipment,
which
is
usually
controlled
by
a
(punched
paper)
tape
containing
the
various
machining
instructions.
In
numerical
control
of
machine
tools,
servo
motors
replace
human
operators
in
the
positioning
of
the
work
piece,
and
positioning
and
operation
of
cutting
tools.
The
use
is
made
of
electronic
devices
which
receive
operating
instructions
stored
on
punched
tape
to
activate
electric
motors
that
position
the
work
for
machining
On
some
N/C
machines,
tool
change
and
speeds
and
feed
are
controlled
by
instructions
punched
into
the
tape.
Numbers,
letters
and
symbols
gathered
together
and
logically
organized
to
direct
a
machine
tool
for
a
specific
task
are
called
an
NC
Program.
Most
automated
machine
tools
are
uneconomical
for
small
runs,
custom
made
products
or
job
lots.
Numerical
control
not
only
makes
such
production
possible
but
also
economically
desirable.
N/C
has
the
advantage
of
the
precision
and
uniformly
high
quality
as
made
possible
by
automation.
Numerical
control is
ideally
suited
for
the
small
batch
production
of
parts,
particularly
very
complex
parts
which
require
great
skill
on
the
part
of
a
machine
operator.
It
is
also
suited
for
larger
batch
production;
the
tapes
can
be
stored
so
that
the
machine
can
be
quickly
set
up
at
any
time
and
the
same
programme
used.
N/C
machines
are
generally
economical
for
the
machining
of
those
medium
components
that
are
required
in
small
batches
and
do
not
need
a
wide
variety
of
machining
operations
using
different
tools
and
different
positions
of
the
work
piece
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