Computer numerical control (CNC) is the automation of machine tools by means of computers executing pre-programmed sequences of machine control commands. This is in contrast to machines that are manually controlled by hand wheels or levers, or mechanically automated by cams alone.

In modern CNC systems, the design of a mechanical part and its manufacturing program is highly automated. The part's mechanical dimensions are defined using computer-aided design (CAD) software, and then translated into manufacturing directives by computer –aided manufacturing (CAM) software. The resulting directives are transformed (by "post processor" software) into the specific commands necessary for a particular machine to produce the component, and then are loaded into the CNC machine.

Since any particular component might require the use of a number of different tools –drills, saws, etc. – modern machines often combine multiple tools into a single "cell". In other installations, 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 series of steps needed to produce any part is highly automated and produces a part that closely matches the original CAD.

Example Of CNC Machining:

%

o0001

G20 G40 G80 G90 G94 G54(Inch, Cutter Comp. Cancel, Deactivate all canned cycles, moves axes to machine coordinate, feed per min., origin coordinate system)

M06 T01 (Tool change to tool 1)

G43 H01 (Tool length comp. in positive direction, length compensation for tool)

M03 S1200 (Spindle turns CW at 1200RPM)

G00 X0. Y0. (Rapid Traverse to X=0. Y=0.)

G00 Z.5 (Rapid Traverse to z=.5)

G00 X1. Y-.75 (Rapid traverse to X1. Y-.75)

G01 Z-.1 F10 (Plunge into part at Z-.25 at 10in per min.)

G03 X.875 Y-.5 I.1875 J-.75 (CCW arc cut to X.875 Y-.5 with radius origin at I.625 J-.75)

G03 X.5 Y-.75 I0.0 J0.0 (CCW arc cut to X.5 Y-.75 with radius origin at I0.0 J0.0)

G03 X.75 Y-.9375 I0.0 J0.0(CCW arc cut to X.75 Y-.9375 with radius origin at I0.0 J0.0)

G02 X1. Y-1.25 I.75 J-1.25 (CW arc cut to X1. Y-1.25 with radius origin at I.75 J-1.25)

G02 X.75 Y-1.5625 I0.0 J0.0 (CW arc cut to X.75 Y-1.5625 with same radius origin as previous arc)

G02 X.5 Y-1.25 I0.0 J0.0 (CW arc cut to X.5 Y-1.25 with same radius origin as previous arc)

G00 Z.5 (Rapid traverse to z.5)

M05 (spindle stops)

M30 (Program End)

%G00 X0.0 Y0.0 (Mill returns to origin)

Having the correct Speeds and Feeds in the program provides for a more efficient and smoother product run. Incorrect speeds and feeds will cause damage to the tool, machine spindle and even the product. The quickest and simplest way to find these numbers would be to use a calculator that can be found online. A formula can also be used to calculate the proper speeds and feeds for a material