Assignment: Spend a handful of hours evaluating your assigned 3D modeling software (Blender)
Blender doesn’t seem like a reasonable substitute for Alibre or Solidworks… I’m not even sure CAD suites are on the radar of competing products for the Blender Dev team.
Instead, they’re positioning Blender as an alternative to Maya or 3Ds Max, and extending functionality into game design while basic CAD functionality (measurements, assemblies, alignment) is neglected.
Still, it represents a huge amount of open-source work towards the basic infrastructure required by both 3D Modeling / Animation tools and 3D Drafting / Design tools. Several efforts have been made to implement CAD functionality within Blender, but none of them seem mature enough for production work (or even sustained dabbling).
Of all the small side-projects and forks attempting to take Blender in a more CAD-like direction, the only one with any enduring momentum seems to be BlenderCAD — which proved too unstable for completing even basic work.
This pretty much describes the experience:
I wish the developers luck, though, since the lack of serious open-source CAD tools is a shame. Something Blender-based is probably the last great hope.