In our 3D software we can make any cross section views detail views or what ever you want.
we do the same in plain ol' AutoCAD
How often do you change this model or drawing after you are done with it?
hourly, daily, minute by minute. These things aren't "done" til' oil becomes gasoline. What you're seeing in that model is a dozen different XREF's
How much of this model can be used for other projects?
whatever isn't proprietary. The entire assembly is a one-off custom facility, however the individual components are basic models.
Can you use like a common coupling or screw and move it where you want it? Move it from project to project?
certainly
Like the beams do you draw the new beam every time if the length changes? Or is a modification from the first beam you did?
a couple of lisp function to modify the xscale, or translate the part/assembly change the member shape or whatever. But even without the customization, there's never a need to rebuild the beam from scratch unless the member size changes.
Are all new projects a new clean blank screen start?
mostly, but entry for most assemblies is parametric. tell it how many bents of rack at how many levels and member sizes and spacings and it's built. Or input the FEA data output from RISA, and it builds itself.
Also how do you do your analysis on your 3D models? How do you know your design is strong enough FEA? How do you know your Flows are what they should be CFD?
FEA is RISA, Process is Caesar, E&I is INtools.
Autocad you just model it in 3D and hope it is strong enough and hope the fluid flow how it should.?
only if you don't know how to do it right.
Final comment I guess you can not teach an old dog new tricks.
oh i can pick up a lot of new tricks, I lust have no need to drop a bundle on new software to do it.
Those who say it can't be done are a constant source of amusement to those of us doing it anyway.