Free CAD-CAM CNC software for mechanical engineering

In modern CNC systems, end-to-end component 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 machines for production. 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 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.

Free CAD-CAM CNC software for mechanical engineering:

G-Simple This CNC program is completely free simple yet powerful software for 3-axis mills, use it to create G-codes for drilling, milling, engraving, tapping & pocketing.
Download:
http://www.polaris.com.gr/gsimple/download.html

GCAM is an free Open Source software for 3-Axis CNC mills. Simple interface for making holes, and sketches, which after extruded, provide the cutting paths for the selected end mill. GCAM also supports RS274X (Gerber) and Excellon drill files for circuit board milling..
Download:
http://gcam.js.cx/index.php/Main_Page

30-day trial versions:
http://www.softsquad.com/downloads.htm

Cut2d by Vectric
Cut2D converts CAD DXF and graphics designs to GCode / CNC Toolpaths for machining high quality parts and components, and users say it's easy to use. Price: $149 .
http://www.vectric.com/WebSite/Vectric/products/download_products.htm

We'll be adding more free cnc software sources as we fin them.