Hercules1...taking a step back.... as a designer of your own individual 'complex' as you stated parts you don't need to worry about the mathematics and scientific equations…. unless you are actually writing the CAD software your self….
Also let's not stray from your first post which was to request advice on different CAD software packages with your budget…..
In your last post and in reply to me you stated you didn’t want parametric but free form software…..personally for the price I actually like Alibre Design as a 3D Solid form Parametric software, even though you cannot draft surface drawings for the price it’s extremely easy and user friendly interface and supporting tutorial videos are hard to beat.
I use Alibre for non surfacing designs and some part creation as I find I require less input commands than Rhino for Solid object creation…i.e less time spent wasted converting my design sketches into CAD drawings.
Also all of us who bought and use 3D CAD packages our suggestions may not suit you and your buget……..
So for my cent’s worth my suggestions are to download all the free demos and use them all.......... then and only then make your own mind up as to what will suit your application needs for ease of use, export options and the complexity of your design creations.
You will then be in a better position to make an informed decision based on your own evaluations of the CAD packages.
Other wise you could be here for months listening to all of us telling you how great each of our software products are.