MCAD stands for Mechanical Computer-Aided Design and refers to Software that assists in transitioning Mechanical Design to Mechanical Fabrication (Implementation).

Design data such as MCAD outputs can then be converted into something a machine or machinist can use to fabricate the mechanical part (examples: conversion of an MCAD Output (.STL) into G-Code that a CNC milling machine can then use to subtractively shape a block of material; conversion of an MCAD output (.STL) into G-code that a 3D Printer can then use to additively shape a part)

The following is a great Venn Diagram indicating the overlap of this field with other Software tools: CAD Industry Diagram

Some free 2D and 2.5D Drawing MCAD Sources:

2D applications allow you to specify coordinates in X and Y dimensions. 2.5D applications allow you to specify coordinates in X and Y dimensions, along with simple depth techniques, usually based on drawing on different layers.

  • DraftSight is offered by 3DS and runs on Mac, Linux, and Windows
  • Inkscape is a general purpose vector drawing program that, with specific extensions, is very handy for turning images and text to G-code for CNC use.
  • Please add more

Some free 3D Modeling MCAD Sources:

3D applications allow you to specify coordinates in X, Y and Z dimensions, accurately describing real-world objects.

  • Google Sketchup has been steadily gaining popularity and features. There's also great gallery of preexisting parts.
  • Blender is an open source suite of cross-platform tools for making 3D objects. Very powerful.
  • BRL-CAD is an open source, cross-platform 3D Solid modeling program much like Blender. Very powerful, and used in several government and academic projects.
  • OpenSCAD is open source/cross platform tool that behaves more like a 3D scripting language, constructively building the 3D model. Good for less complex renderings and conversion from 2D drawings to 3D models.
  • Creo Elements/Direct Modeling Personal Edition is a free personal version of commercial software. It's new (5/20/11) and Metis is investigating it.

Tools for Conversion to G-Code (CNC path data) aka CAM:

Just Viewers:

  • Solidworks eDrawings Viewer - for viewing many 3D formats (windows,mac)
  • eDrawings Rapidfire Lite - for viewing many STEP, IGES, STL, Rhino, JT and OBJ files (windows, requires 16-day registration)
  • Please provide more - specifically for STEP and STL!
  • OK Meshlab Open source 3D model slicing, fixing, tweaking tool, multi-platform supports numerous formats, including STL in and out.