Numerical control
CNC redirects here. For other uses, see
CNC (disambiguation).
A CNC Turning Center.
Siemens CNC panel.
Numerical control (NC) refers to the auto-
mation of machine tools that are operated by
abstractly programmed commands encoded
on a storage medium, as opposed to manually
controlled via handwheels or
levers or
mechanically automated via cams alone. The
first NC machines were built in the 1940s
and 50s, based on existing tools that were
modified with motors that moved the controls
to follow points fed into the system on paper
tape. These early servomechanisms were rap-
idly augmented with analog and digital com-
puters, creating the modern computer nu-
merical controlled (CNC) machine tools
that have revolutionized the design process.
In modern CNC systems, end-to-end com-
ponent design is highly automated using
CAD/CAM programs. The programs produce
a computer file that is interpreted to extract
the commands needed to operate a particular
machine, and then loaded into the CNC ma-
chines for production. Since any particular
component might require the use of a num-
ber of different tools - drills, saws, etc. - mod-
ern machines often combine multiple tools in-
to a single "cell". In other cases, a number of
different machines are used with an external
controller and human or robotic operators
that move the component from machine to
machine. In either case the complex series of
steps needed to produce any part is highly
automated and produces a part that closely
matches the original CAD design.
History
Earlier forms of automation
Cams
The automation of machine tool control
began in the 1800s with cams that "played" a
machine tool in the way that cams had long
been playing musical boxes or operating
elaborate cuckoo clocks. Thomas Blanchard
built
his
gun-stock-copying
lathes
(1820s-30s), and the work of people such as
Christopher Miner Spencer developed the
turret lathe into the screw machine (1870s).
Cam-based automation had already reached a
highly advanced state by World War I
(1910s).
However,