Generally speaking 3d graphics differs from CAD in concept. The goal of a CAD program is to produce high quality plans or 3D model for rapid prototype. Whereas a 3D mesh modeling program is intended to create plausibility.
Here is an example; If you design a mechanical part in AutoCAD you have to engineer it down to a fairly tight tolerance or it wont work once its created.
In Blender if you render out a scene it is pretty much impossible to tell if your bracket has a 28 degree radius or a 32 degree radius. Hence if you are close enough you will achieve a desired level of plausibility in less time.
With this in mind you should probably look for efficiencies to make your scene easier to work with and speed up your render time.
Here are some efficiencies that you should consider
do all of you parts really need to be separated and have their own properties? Or instead can you join many small parts into one mesh and then have only one modifier affect everything?
Linked duplicates; Hypothetically if your design has 200 type 8 screws. Then you should create one screw and make all of the others linked duplicates. This way you will end up with 1 object and 198 instances (clones). Since the instances share all of the parent’s properties they occupy much less memory, will render faster, and a change made to one will be applied to all.
Use arrays wherever possible they are far more efficient when it comes to memory usage and render time
Wasted geometry, can you actually see the interior of your bracket. Ie do you plan on animating a disassembly process? If not and you plan to render out a static image, then you will only want to model what can be seen. For example that bracket that you have in one of you earlier posts, it looks like another plate bolts onto the top of that piece, and a shaft goes into the primary hole. If that is the case then you can get by with far less geometry. See Figure A compared to Figure B Comparison.blend (870 KB)
Generally speaking its better to import your CAD data and then use it as a guide while you actually model out each piece in Blender. I know it seems redundant and unnecessary considering that you already modeled it out in a CAD program. However you will be glad when virtually the same model renders beautifully in 30 seconds as opposed 2 hours or more.
If you wish you can upload one of your components and I’ll rebuild it for you, so that you can see this concept demonstrated.